World Cultural Heritage—Solving 10 Mysteries of Nirayama Reverberatory Furnace
T. Kanno
Kimura Chuzosho Co., Ltd., 1157 Shimizu-cho, Shizuoka Prefecture, Japan
Key-Words: Nirayama reverberatory furnace, World Heritage, Cannon, Cast iron, Pig iron, Melting temperature,
Bellows, Fuel, Firebrick
1. Introduction
Nirayama reverberatory furnace is located in Izunokuni
city, the Izu Peninsula, Shizuoka Prefecture. As shown in
Fig. 1, they are composed of four furnaces in total: twopairs of twin towers, 15.6 m in height.1) Though the existing
reverberatory furnace is also in Yamaguchi Prefecture,
Nirayama’s is the only existing one which was actuallyused to melt cast iron in the world. Being one of theconstituent properties of “Sites of Japan’s Meiji Industrial
Revolution: Kyushu-Yamaguchi and related Areas,” it was
decided to be the government’s recommendee for the World
Heritage registration in 2015, on September 17th, 2013.
Every year one site is selected in the aim of promoting
domestic cultural properties for inclusion on the World
Heritage List.
This application aims to register as one of the group of“Heritages of Industrial Modernization in Kyushu area andYamaguchi,” not Nirayama’s individually. The group iscomposed of 8 areas, 11 sites, and 23 properties, including
the castle town in Hagi city, Shuseikan in Kagoshima city,
Nirayama reverberatory furnace in Izunokuni city, Hashino
blast furnace in Kamaishi city, Mie Tsu Naval Training
Center in Saga city, Hashima Coal Mine and Glover Housein Nagasaki city, Miike Coal Mine in Arao city and Omuta
city and Yahata Steel Works in Kitakyushu city. Somepeople judge the value of a reverberatory furnace by its
capability to melt cast iron, but we think otherwise. The
purpose of the application is to hand down to posterity oneof the important assets in human history which contributed
to “spread of industrial modernization throughout Asia.”
ICOMOS, an advisory body of UNESCO, advised them toinscribe these sites on the World Heritage List on May 4th,2015. On July 5, 2015, World Heritage list registrationof "Sites of Japan's Meiji Industrial Revolution"
including Nirayama reverberatory furnace was decided.
What is important for the registration is local residents’cooperation in its preservation and enhanced interest in it.
Under these circumstances, we had activities to raise public
interest. We produced miniature cannons by a cupolafurnace and hosted a workshop for kids to make accessories
by casting on February 24th, 2013, when Symposium for
Registration of Nirayama reverberatory furnace was held.
As shown in Fig. 2, thanks to the cooperation of Mr. Murata,
the president of Naniwa Roki, we could show cupola-style
casting in the open. Since then about 40 children haveparticipated in the workshop every year.

Fig. 1 Nirayama reverberatory furnace and 24
pounderFig. 2 Cupola (*1) and casting workshop*1 Cupola: a furnace to obtain molten cast iron that does
not get chilled, using combustion heat of coke. Nagasaki
Ironworks’ is the first cupola built in Japan. The
principle in melting is the same as that of a blast furnace.
Japanese original furnace koshiki is also the same inprinciple but the only difference is its fuel--coal andcharcoal instead of coke. The furnace is named after anearthen vessel, koshiki, used to be a tool to steam rice,
whose shape resembles to that of the furnace. Althoughkoshiki tends to be confused with tatara, they are not thesame and have different shape. Tatara is a furnace tomake tamahagane, special steel to process into Japaneseswords.
1

It was 20 years ago, around July in 1997, when I first got
involved with the reverberatory furnace. There was aconcern that it was inappropriate for Nirayama to exhibit acement cannon, from Prof. Madono, an authority in casting,and Prof. Nakae, my former teacher of Waseda University.
In March the next year, we Kimura Chuzosho Co., Ltd casta 24 pounder and donated it to Izunokuni city. It wasaround 2004 when I began in earnest to investigate thefurnace with all my family. Of my children, so young 13
years ago, my eldest son and daughter have become
members of society while my second son and second
daughter have grown up to go to university (Fig. 3). Prof.
Nakae, who afforded me the opportunity to produce thecannon, currently serves as the chief investigationcommittee member of National Museum of Nature andScience. With Firearms Historical Academy of Japan, he ismaking a detailed survey of cast cannons from the closingdays of Tokugawa regime to Meiji era, based on aperspective of casting engineering.
Here I unravel mysteries of producing cannons with
Nirayama reverberatory furnace beyond time, weaving into
this article the studies by Prof. Nakae, an adviser of Kimura
Chuzosho Co., Ltd at present, and ours on the furnace.

people's first encounter with iron was realized by meteorite.
In Egypt, an iron necklace made from meteorite around3000 B.C. was found. Thus, the first processing method of
metals was forging. Beating, that is, forging gradually
pushes out dust and impurities included in metal. Carbon
also get eliminated into outside. Human beings haveeliminated impurities from metal with hammering,
controlled carbon contents, and made tools and weapons fora long time. Come to think of it, Japanese sword is the mostadvanced forging product in the world.
The casting technology by pouring molten metal into amold and solidifying started in 3600 B.C. at Mesopotamia.
It was approximately 5600 years ago. Pouring molten
bronze into a mold is considered as the beginning.3) It is the
beginning of Bronze civilization, that is, the beginning of
casting. This means casting has 5600 years history.
The situation that people cast a door while sending windwith stepping bellows (*3)was described in an Egyptian
papyrus of about 1500 B.C. in Fig. 4.4) Humans could gethigher temperature by the invention of bellows, and theBronze Age reached the golden age. By the way, themelting point of bronze is approximately 800°C with Cu25%Sn. Considering pouring, it has a possibility that themelting temperature had exceeded 900-1000°C.
*3 Bellows: A manual or treadle blower which is simply

structured. Bellows were used for furnaces small in size tosend air to the fuel.

Fig. 3 My children and climbing kiln (*2)

*2 Climbing kiln: the characteristic is that it consists ofseveral chambers built stepwise on a sloping land. It is
structured to send heat, smoke, and ash from the bottom,
where firewood is burned, through chambers into thekiln top. In Japan, it started from Edo period (1610),
famous for early Imari ware. Even today, it is burned atabout 1200-1250°C. This temperature is 50-100°C
higher than the melting temperature 1153°C of the highcarbon cast iron. Around the climbing kiln at Nashimoto,much alumina white clay is seen, and it is conceivablethat people burned firebricks made with the clay.

Fig. 4 Casting bronze doors (around 1500 B.C. in
Egypt)

Since iron is oxidized on earth, it cannot be used as iron
if not be deoxidized. It has been believed that in 1700 B.C.,
the Hittite empire first obtained much iron by deoxidizing
iron ore. People used a batch-type furnace which
deoxidized iron sand by charcoal, and took out spongiform
pure iron which gathered at the bottom of the furnace. Theyobtained ironware by heating and forging that iron. It was

2. What Is a Reverberatory Furnace?
2.1 History of Metal and Casting
Human beings have first encountered metals in 50006000 B.C. when people were processing natural
gold/silver/copper by hand beating.2) It is thought that2

written in an epic poem of Homer in the eighth century B.C.
that iron was highly expensive. Probably, the price of ironwas 5-10 times as high as that of gold. Iron has a defect that
it is easy to rust unlike gold and bronze. Therefore, only
few historical relics of iron are left because they have rusted
and returned to soil. The technology of producing iron has
spread throughout Europe because Hittite empire lost at
Trojan War, famous for the Trojan horse and Achilles, inabout 1200 B.C.
Strangely, the iron production by forging has continued
until the fourteenth century, but casting, a method in whichmolten metal is poured into a mold, has not been started
until after the fourteenth century. Also, it is thought thatsaber became a European weapon, considering thedifference in history of how to produce iron.
The casting technology of pouring molten iron instead ofbronze into a mold, was developed in China in the earlyseventh century B.C.5) China is thought to have had atechnology to generate considerably high temperature withbellows in bronze production. Apparently this technology
allowed them to make various tools by melting the ironwhich had high carbon composition (generally, it is called
cast iron when its carbon content is more than 2.1%). While
the melting temperature of low-carbon iron composition is
1536℃ and high, that of high-carbon cast iron is 1153°C
and low. This low-carbon iron enabled iron casting for its
excellent flowability. The composition of the casting iron ofaround fourth century B.C was C2.5-4.3%, Si0.1-0.2%,
Mn0.01-0.2%, P0.1-0.5%, S0.01-0.1%.3) The Si content
was higher than Japanese cast iron (less than 0.1%), so it ispossible to assume that they have gotten high temperature.
However Si even in the composition of this cast iron was
also low. It became a hard and brittle material that is called
chill (*4) and didn’t have graphite.
This chilled cast iron is hard and brittle, so it has thebiggest disadvantage that it cannot be machined. It isdifficult to machine the chilled cast iron even with present
machines. The microstructure of the hard and brittle chilledcast iron is shown in Fig. 5. As there is little graphite in thischill casting, it makes good sound like a wind-bell. On theother hand, in the modern cast iron which can be machined
shown in Fig. 6, some flake graphite comes out, and its
ability to absorb sound vibration is high. If a wind bell ismade with current machinable cast iron, the sound would
hardly come out. The modern cast iron is used for basematerials of machining tool or industrial equipment, withtaking advantage of vibration absorbing quality.
In China, they produced whiteheart malleable cast iron(shown in Fig. 7) in about 470 B.C. by heating this cast iron(shown in Fig. 5) in about 900-1000°C oxidized iron forthree days6). The celebrated swords which belonged to Cao
Cao and Zhuge Liang in the era of the Three Kingdoms are
assumed to be made by heat treatment(*5)and forging thismalleable cast iron to adjust the amount of carbon.
According to a book on industrial technology published in
1637, Heavenly Creations, wrought iron was createdalready during Han dynasty around the second to the third
century B.C. as shown in Fig. 8. Their wrought iron is thesame as that later made through puddling process using areverberatory furnace which Henry Cort invented in 1784.7)
In China, from this drawing, using bellows and a blast
furnace like koshiki enabled to obtain molten iron of aconsiderably high temperature. Historically, the whiteheart
malleable cast iron (iron close to modern steel which has nographite in Fig. 7) was invented by Réaumur in France in
1772. Also, blackheart malleable cast iron (shown in Fig. 9)
was produced by Boyden in America in 1826.8) Even today,
malleable cast iron is infrequently used, but the amount of
production has decreased, because spheroidal graphite castiron (shown in Fig. 10) was invented by Morrogh in 1948.
By the way, some of the parts requiring excellent
elongation of Brunat’s engine used in Tomioka Silk Mill,
designated a World Heritage in 2014, are turned out to bemalleable cast iron from my investigation.
The Chinese iron history changed from bronze to chill
casting, to malleable cast iron made by heat treatment, andthen to wrought iron.

Graphite

GraphiteFig. 5 Microstructure of oldchill casting which is hardand brittle (*4)

Fig. 6 Microstructure ofmodern machinable cast iron3

Fig. 7 Microstructure of white heart
malleable cast iron same as that ofsteel which made from chill
casting.7)

*4 Chill casting: Originally, chill has the meaningof cooling or cooling down. In a casting process,the speed for molten metal to cool down iscontrolled by putting pieces of metal called
chillers outside of a mold, and if the speed is too
high, it would be a chill casting with no graphite,and be a defective. From this experience, as theparts which were put chillers to often formed chill,so those parts became called chill. Anyhow,
unless casting includes some Si or high carbon, it
would become easily chilled cast iron. Chill
casting is too hard to machine.
*5 Heat treatment: A process to achieve a desired
property by heating and cooling iron, steel, andnon-ferrous metals at below the melting point.23)
For example, as mentioned above, Réaumur
developed a method to turn chill casting into steellike iron by heat treatment.

Fig. 8 Refining furnace of cast iron and wrought iron7)

GraphiteFig. 9 Microstructure of
blackheart malleable cast ironmade of heat-treated chill
casting.9)

GraphiteFig. 10 Modern spheroidal
graphite cast ironThis brittle characteristic of chilled cast iron seems to bea cause that iron casting technology had not been
introduced to Europe until the fourteenth century. Therefore,
from the seventh century B.C. to the eighteenth century of
the Industrial Revolution in Europe, cast iron was hard andbrittle. Also, in Japan, chilled cast iron was used mainly
until the end of the Edo period before blast furnaces wereintroduced. No wonder for forged iron made by hammering
was valued in Europe and Japan, as it has a good viscosity,
gets hardened by quenching, and is made by hammering.
Meanwhile in China, people produced malleable cast ironby heat treatment to chilled cast iron, and they had gotten
materials like steel (shown in Fig. 11). From Heavenly
Creations, they seem to have made wrought iron using sortof blast furnaces with bellows.
Increasing silicon (Si) content changed cast iron’s
property largely. Iron Bridge was built in England in 1779,
when high silicon and non-chilled cast iron was developed(Fig. 12). In England, Darby the second achieved producing
cast iron with a blast furnace, and high silicon cast iron
began to be produced. Because non-chilled cast ironFig. 11 Microstructure of steel（S25C）

appeared, cast iron became machinable for the first time. It
enabled to produce steam engines, and led to the Industrial
Revolution. In such meaning, cast iron was the mother of
the Industrial Revolution, and is an important material tosupport industry nowadays.

Fig. 12 The Iron Bridge made from non-chilled flake
graphite cast iron, in 1799 (World’s Cultural Heritagein Coalbrookdale, UK)In summary, there were four types of cast iron: (1) iron toforge, (2) hard and brittle chill casting, (3) the hard and4brittle chill casting softened by heat treatment, and (4) akind of iron called wrought iron which requires hightemperature to create as China succeeded using bellows.
When seeing metal history in terms of reduction of oxide,
you may find some interesting things. Fig. 13 shows thegraph of the relationship of stability and temperature ofoxides.

without chill, while malleable cast iron was not fit for large
and thick castings. The best days of casting are from theinvention of a blast furnace till that of a converter. A
reverberatory furnace was invented by Thomas and George
Cranage in 1766, behind success of a blast furnace. It is atechnology to re-melt pig iron (*6), which was made with ablast furnace in advance, by burning coal in a reverberatory
furnace. This invention made it possible to get large amountof molten cast iron independently of a blast furnace. Notethat it is not in 1766 when a reverberatory furnace itself wasinvented, but it was already in use to melt copper and leadin low temperature. After that, in 1772, Réaumur invented
whiteheart malleable cast iron (modern iron similar to steel),which is made by heat-treating chill casting. In 1784, Henry
Cort developed a method to reduce amount of carbon to
produce steel (wrought iron) by puddling molten metal in areverberatory furnace (puddling process). The wrought ironis a kind of steel which contains 0-0.25% of carbon. The
process is as follows: first put iron oxide into areverberatory furnace and reduce amount of carbon throughreaction between the molten pig iron and iron oxide (FeO +C → Fe + CO ↑). Then puddle the iron with rods to make asteel ball, which is later forged into steel. Therefore
reverberatory-furnace wrought iron had a fault that 10-20%
inclusion remains inside due to the slags(*7). Through thisprocess, about 200 kg of steel (wrought iron) is created at atime. The Eiffel Tower, built in 1889 for Universal
Exposition, was made of this wrought iron. Its iron frames
weigh 7000 t, which gives us the impression of a big project.
By the way, the Tokyo Tower weighs 4000 t, and theSkytree 36,000 t only above the ground part. In China, as
mentioned above, wrought iron was made during Han
Dynasty, from the third century to the second century B.C.,
through puddling process. In the literature it is often
described simply as iron was produced with a reverberatory
furnace through puddling process. I need to emphasize themeaningful change as follows: the furnace was used (a) tomelt copper or lead which has low melting temperature in
the early period, (b) to re-melt pig iron which was made bya blast furnace in the middle period, and (c) to produce
wrought iron with puddling process. Puddling process was a
way to produce another kind, wrought iron (Table 1).

Fig. 13 Relationship of temperature and stability ofoxidesSeeing the Fig. 13, all materials become unstable withincreasing temperature, because the atom vibration becomeslarge. It is the same as changing from ice to water and to
steam with increasing temperature. However, only carbon
monoxide (CO gas) becomes stable with temperature riseapart from this law of the universe. It is the special material
which becomes more stable if the temperature gets higher.
Thanks to existence of carbon monoxide, humancivilization was born and built up by reducing oxidized
metal. Let’s take copper as an example, in Fig. 13. Copperoxide is reduced to copper when it is put among charcoal(carbon) whose temperature is kept over 155°C, about as
hot as a bonfire. We could know from Fig. 13 that the lower
the reducing temperature is, the older history metal has. I
described previously that production of non-chilled castingneeds silicon, that Si became possible to get from silica
stone (including much SiO2). It was after A.D. 1700, when
the furnace capable to reach higher than 1600°C wasdeveloped. Thinking this way, we can say that humancivilization has fought against temperature.
2.2 Historical Position of a Reverberatory Furnace
As mentioned above, it was in 1735 when Darby second
enabled to make machinable high-silicon cast iron using a
blast furnace in Britain. His machinable cast iron became
the most significant material for a steam engine. The engine
worked as a device to blow strong wind into a blast furnace,
generating high temperature inside. The point of his
invention is that it enabled to produce machinable castings
5

Year
1735
1766

Reverberatory-furnace age (forabout 90 years)

about 70 years)(for age (for about 70
years)

Steelage

Wrought iron age (forCast iron age (forabout 50 years)

Table 1 Historical Position of Reverberatory Furnace

Furnace and material
Blast furnace and castiron
Reverberatory furnaceand cast iron

Inventor
Darby thesecondThomas andGeorgeCranageRéaumurContents and historical importance
Enabled producing machinable high-silicon cast iron.
Enabled to get large amount of molten cast ironindependently of a blast furnace, by re-melting pig iron(*4) made with a blast furnace.
Turned iron similar to steel by heat-treating theunmachinable chill casting.

1772

Whiteheart malleable
cast iron

1784

Reverberatory furnacewith puddling process
and wrought ironHenry Cort

Made wrought iron by puddling molten iron in areverberatory furnace and reducing amount of carbon(puddling process): the Eiffel Tower, built for Universal
Exposition in 1889, is made of wrought iron

1856

Bessemer’s converterand steelBessemer

Enabled to make steel whose carbon content is under
2.1% directly from molten iron, while that had needed
forging before.

*6 Pig iron: It is a general term for iron materials processed into steel or cast iron. In old times they were called zuku. Createdby reducing iron ore (iron oxide) with high-carbon cokes or charcoal, pig iron includes much carbon and impurities.
*7 Slag: Unwanted substances produced in melting process due to reactions among metal oxides, solvents and lining

materials. 23) It is required to prevent slags from entering into space of molds because they can cause defects. In operations at
Nirayama, it is considered that they took slags out through the slag hole first, and then poured metal through the tap hole.
As explained in the history of casting, it was since
Bessemer’s invention of a converter in 1856, when it
became possible to get steel, not the forged type but one
with carbon content under 2.1% directly from molten metal.
By the way, some of the parts requiring excellent
elongation of Brunat’s engine used in Tomioka Silk Mill,
designated a World Heritage in 2014, are turned out to bemalleable cast iron from my investigation.
In response to the changes of the times from Darby thesecond’s cast-iron manufacture by a blast furnace to steel
manufacture by a converter, reverberatory furnaces during
the Industrial Revolution in Britain, gradually shifted its
shape: to those to melt cast iron independently of blast
furnaces, and then to those to make steel called wroughtiron. By the way, malleable cast iron cannot be obtained byheat-treating non-chilled cast iron. The main reason why
reverberatory furnaces were used to produce cannons in
Europe is as follows: first, they could obtain from blast
furnaces non-chilled pig iron with high silicon content.
Secondly, they were the most appropriate to get large
amount of molten metal, and in the third place,reverberatory furnaces made it possible to reduce carbon
content from 4.3% to 3.2% to produce castings with highstrength. It is a kind of refining to reduce carbon in areverberatory furnace, but not such refining as to remove
impurities in a converter.

3. Could They Cast Iron Cannons with Nirayama
Reverberatory Furnace?
3.1. Consideration from the Structure of Nirayama
Reverberatory Furnace
Fig. 14 shows the structure of Nirayama reverberatory
furnace. It is constituted of four furnaces and a pouring
platform, 2.7 m deep. Each chimney is 15.6 m high, 5.0 mwide, and 6.0 m long. Fuel such as charcoal, coal or coke
was burned on its fire grate. Then metal materials were put
through a hole into the hearth and were melted with heat of
the furnace. With koshiki, the iron material was made inadvance as the following size: 10 cm wide, 10 cm long, and100 cm high. Molten metal and slags go down the slope tothe tap, where they gather. Stirring the liquid with rods
through hoko, a square hole, evens out its temperature andaccelerates the separation of metal and slags. As following
describes, the South furnace, which was built earlier, has astructure to focus radiant heat around the materials, whilethat of the North one, built later, focuses it on molten iron.
The chimneys are narrowed with a dent at the bottom. Suchstructure, called misaki, prevents heat from getting out andat the same time draws a more draft due to Venturi effectwhich is caused by change in pressure in the chimneys.

6Fig. 14 Structure of Nirayama reverberatory furnace1)

OthersBricksHow to melt

Table 2 Unsolved mysteries of Nirayama reverberatory furnace and general opinions

Unsolved Mysteries of Nirayama
reverberatory furnace
1. Was cast iron melted with Nirayama
reverberatory furnace?
2. How high was the melting
temperature?
3. How long did it take to melt materials?
4. Was metal poured directly into a mold,or into a ladle (*8) before pouring?
5. Were bellows used?
6. What was the fuel? Was coke used?
7. What kind of material were used, ironsand from Iwami, gantetsu (iron ore)from Iwate, imported pig iron (Nambaniron) (*9), or ballast?
8. Where were the bricks forming thefurnace fired?

9. How many cannons were produced,
and finished at Nirayama?
10. Defects caused by compositions ofcast iron cannons

General opinions
Because the iron starts to melt at 1600°C, the temperature in the furnace
did not go up high enough to melt iron.

It took long because they used charcoal as fuel.
They used a ladle because the furnace has a facility to install a crane tolift it.
They did not use bellows as Venturi effect allowed the firebox to draw adraft.
They did not use coke.
While Saga domain (*10) used ballast, gravel placed at the bottom of aship, Nirayama did not.

Nashimoto in Kawazu-cho and the hill behind Nirayama reverberatory
furnace

Two iron cannons and 128 cannons including bronze ones.
It included many impurities such as titanium and sulfur. In addition,molten metal’s temperature was not high.

Table 2 summarizes the unsolved mysteries of Nirayama
reverberatory furnace. As to general opinions seen in theliterature, authors avoid clear expressions, ending up in
ambiguous answers. I am going to examine the mysteries
by comparing the literature with my own experiments.
Visitors would doubt that iron was actually melted withsuch a small, simple furnace. Due to this impression many
people deduce that it was impossible. First, it is necessary
to emphasize that the material was not pure iron whose

melting point is 1536°C, but cast iron, with a carbon
content of over 4.3%, melting point 1153°C. If the cast ironis composed to solidify at 1153°C, the sufficienttemperature to melt it (the melting temperature) is about
1250°C, which is 100°C higher. It is slightly higher thanthat of the kiln used to fire bricks because the temperature
in it was between 1200°C and 1250°C.

7

Fig. 15 is the reverberatory furnace depicted in theCasting Method at the Royal Liege Foundry for Iron
Cannons written by U. Huguenin. It has a hearth sloping at
a greater angle and no cavity under the ground. Except
those differences, it is highly congruent with Nirayama’s interms of the misaki and the shape of the furnace.
Takisho hunyuko is an entrance of air into the firebox(Fig. 16). By Venturi effect of the chimney, a large quantityof air is drawn through it. There are firebricks marked witha circle in many parts of this hole or the furnace. They wereburned in Nashimoto, Shimoda, where they were used toconstruct a local reverberatory furnace, and then later they
were brought to Nirayama. From the bend of the cast-ironbar of a fire grate at takisho hunyuko, you could see howhigh the temperature went up there.

Fig. 15 Reverberatory furnace drawn in theCasting Method at the Royal Liege Foundry for Iron
Cannons owned by the National Diet LibraryFig. 16 Entrance of air into firebox
Arched plate

Izu stone

Arched plate

Compositions of cast-iron materials made at reverberatory furnace, %Iron
Arched panel

Lintel

C
3.5
4.2

Si
0.016
0.02

Mn
-

P
0.14

S
0.026
0.014

Cu
-

Ti
0.003
0.008

Fig. 17 Arched plates and Izu stones1)*8 Ladle: A heat-resistant vessel to transport molten metal from the tap hole to molds. Depending on the size of castings, theshape varies from a large spoon with a long handle to a large pot carried with a car or an overhead crane. Compared to themethod to pour metal directly from the tap hole into a mold, the poured melt’s temperature decreases by around 100°C whenthe metal is collected in a ladle before transportation.
*9 Namban iron: Iron produced in India. During the Age of Civil Wars (around 16th century), Japan imported Namban ironthrough intermediatry trade with Portugal to deal with a shortage of iron for swords and guns. The iron was preferred material
as well as ballast. However, a survey revealed that Namban iron was chill casting unmachinable for its low Si content.
*10 Saga domain: A domain located in the northwest Kyushu. The feudal lord at the time, Naomasa Nabeshima, wasenthusiastic about introducing Western techniques, encouraging medical science and military theory in his domain. Aftertranslating Huguenin’s book by his command, they built a reverberatory furnace and cast an iron cannon for the first time inJapan. Their cannons were trusted so high that the Tokugawa shogunate made a large order. Due to their outstanding ability,
Saga domain had a significant influence on Japan’s coastal defenses.
8Hole forMetal materials

Fire door

Fig. 18 Holes to put metal materials onto fire grate and to put fuel into firebox

Square hole

Hole formetal materials

Fire door

Slag hole
Hole formetal materials

Tap hole

HearthFire grate

Fig. 19 Inside of reverberatory furnace1)

Slag hole
Tap hole

Fig. 20 Tap holes and slag holes

The cavity under the bottom of the furnace has an archedceiling, which is made of metal plates bent semi-circle andthe plates are supported by Izu stones (Fig. 17). The ceilinghas square holes so that water from the hearth drops
through them without mixing with molten iron. The idea
seems to belong exclusively to Nirayama as Huguenin’sbook does not mention such a structure.
A hole to put through cast iron made by koshiki, isunusually big meanwhile takiguchi, a hole to put fuelthrough, is not so (Fig. 18). It is said that all materials weremore, refining is all the more unnecessary. The reason will
be explained later.

put into the hearth from the beginning of melting, but its
largeness is nevertheless incomprehensible.
Like a climbing kiln, inside of the furnace is coated withglass apparently for the purpose of reflecting radiant heat(Fig. 19). The slag hole is a hole to discharge slags, and thetap hole is a hole to tap molten iron. Hoko, a square hole, ismade to get rods through and stir slags and the metal.
Though some insist that iron was refined by puddlingprocess, I regard such refining as removing impurities was
not done. As for cast iron with carbon content of 4.3% andFrom outside of the reverberatory furnace, hoko, the slag
hole, and the tap hole can be seen (Fig. 20). Just in front of
the tap hole, there is a pouring platform to set a mold on.
9Because it is built so close to the tap hole, molten metal isconsidered to have been poured directly through it. As forthe mystery of the platform, I will mention it later.

diary that they conducted a firing test on at least one castiron cannon, though the pig iron had some problems.
The diary shows that crews of Perry’s black ships broke
into the construction site of Shimoda’s reverberatory
furnace, which caused transferring the site to Nirayama.
Also until Sugitani from Saga domain arrived, they weremaking metal flasks for cannon production with the South
furnace. For flasks, chill casting was enough. With thecooperation of Saga, on September 9th, they cast an 18
pounder for the first time with the South furnace. The helpof engineers from Saga domain was indispensable. They
started to drill the barrel of the first 18 pounder on
December 4th. Though it is recorded that machining
continued until February 17th, no information about thecannon after that appears in the diary. Probably it had someproblems to be used in actual combat. The South furnace
which was used to produce the first cannon had a structure
to concentrate heat not on molten metal but on metalmaterials, which is revealed by the study of Nirayama highschool students as following describes.

3.2 Consideration from the Operation Record of
Nirayama Reverberatory Furnace
Table 3 shows the excerpts from the operation record of
Nirayama reverberatory furnace (hereinafter referred to as
the reverberatory furnace diary). 1) According to thereverberatory furnace diary, they produced at least three 18
pounders from cast iron. Also orders were placed for 60 t ofcoal, 10,000 bales of Amagi charcoal (also used for baking
bricks), and lime and oyster shells as flux to soften slags.
As metal materials, they ordered 43 t of pig iron and 13.7 tof iron (equivalent to 12 pieces of 18 pound cannons), 2700
kg of copper, 270 kg of tin (this copper-tin ratio is exactly
equivalent to bronze which contains 10% tin). Consideringthat the majority of the total orders is associated with iron, I
have no doubt Nirayama reverberatory furnace was built forthe purpose of melting cast iron. Also you can see from theTable.3 Excerpt from the operation record of Nirayama reverberatory furnace1)

Year
1853

Date
DecemberJanuary
February 1
February 17
March 4
March 8March 16
March 18
March 27
April
April 6
April 9April 17
May 29June 4
July 25
July 18
July 22
August 8
August 14
September 17
November 4

Event[Shimoda, Izu]
Prepared for the construction at Takoma, Shimoda.
Mined white clay at Nashimoto.
Leveled the ground for the construction of the reverberatory furnace.
Started to produce firebricks.
Perry’s black ships entered the port of Shimoda.
Gave notice of sending Edo pig iron.
The ridgepole-raising ceremony of the house for boring machines took place.
Pig iron arrived from Osaka.
Foreigners broke into the construction site.
Purchased 60 t of Chikugo coal
10,000 bales of Amagi charcoal.
Ordered to transfer the construction site.
Joban coal 6 t
Shipped foundation stones. All directors departed.
[Nirayama, Nakamura]
Off-loaded building materials at Numazu.
Sorted firebricks to send on.
Ordered two bales of lime and four bales of oyster shells.
Started to lay firebricks.
Cast iron slabs.
Cast front slabs for an 18 pounder.
Cast iron slabs for an 18 pounder.
Started to plaster walls.
The major earthquake of Ansei (Nothing wrong with the reverberatory furnace)

10

1855

January 16
February 21

April 23

1856

AugustDecember
April 111857

February 5
July 1
September
September 9
November 7
November 19
December 4
December 6

1858

January 8
February 22
February
the last day
March

March 13
March 22
October

1859

January 25
August 21
October 28
1860
January 5
From July 1863 to
February 1864
1864
NovemberZaemon Taro Egawa died.
Cast with one of the first furnace pair.
At 1:00 cast 2 t of pig iron as the first operation of the furnace.
At 11:00 cast a metal flask for an 18 pounder.
At 13:00 operation ended.
A foundry expert, Kuno, arrived at Nirayama for consulting about a metal flask for a 36
pounder.
Requested Saga domain to help Nirayama.
Saga domain accepted the request.
Finished construction of the tar factory.
Cast four times in this month.
Sugitani arrived from Saga. (The first furnace of the South furnace pair was almost
finished.)
Test operation with the South furnace
Test operation with one of the East furnace pair
Test operation with metal flasks
Poured into an 18 pounder mold.
Started at 1:00 and finished pouring at 12:00.
Operation started with the second North furnace. [Pig iron 2270 kg]
Operated with the second South furnace. [Pig iron 2660 kg]
Started to machine the 18 pounder.
Started at 4:30 and ended at 2:16.
The second furnace (the North furnace)[Pig iron 4500 kg] (Used two furnaces) (Probably the second 18 pounder)
Machined the first 18 pounder. (Continued until February 17th.)
Cast the third 18 pounder. [4870 kg]
Cut off the riser. The cannon had no shrinkage cavity.
Finished building one of the triple boring machines.
Using pig iron made with Nagasaki’s blast furnace, it is possible to produce cannons
same as those Western-style. However, the usual pig iron would be used for cannons forurgent orders, because the result of tests showed that the cannons made with the usual pig
iron had a good endurance.
Firing test on the third 18 pounder
All dispatched members from Saga domain departed.
Answered on casting bronze cannons to the government.
A reverberatory furnace for bronze castings has no chimney, which reduces the internal
temperature down to one-seventh. Being poured into a sand mold in a wooden flask, acannon became poor in quality. A metal flask was better.
Four bronze 80 pounders and a 24 pounder
Ordered to produce a bronze 80 pounder and a 24 pounder.
Repaired the reverberatory furnace.
Repaired the chimney of the first furnace which had been badly damaged.
Cast a cannon with the trainees dispatched from the kobusho military academy and persons
concerned with the Egawas. The product was mostly defective.
A suggestion was made that Nirayama reverberatory furnace should be discontinued.

*11 Kikko pattern: A pattern formed over the surface of molten cast iron. Oxide film is generated over the surface of molten
metal. Torn and drifting, this film forms various types of patterns. The patterns have been an indicator of the quality ofmolten metal throughout the ages because they are affected by temperature, chemical composition, and oxidation level. Our
experiment shows that the requirement for formation of the patterns are the following four points: S content of over 0.02%
and Si content of over 0.5%, generation of SiO2 film, and appropriate content of C. Bamboo leaves, pine needles, andhexagons are the typical patterns. Of these patterns, the hexagonal pattern is called kikko (turtle shell) pattern, as hexagons
arranged side by side look like the pattern of a turtle shell.
11For the third 18 pounder which was cast with the North
furnace on February 22th, 1858, 1125 kg of kikko pig iron(*12) was used (Fig. 21). Kikko (*11), a turtle shell, is thesame name as the hexagonal type of patterns formed on
molten metal’s surface, which is described later. As thetotal amount of the melted material is 4870 kg, the pig ironaccounts for 23% of it. On the other hand, no mention ismade about kikko pig iron in the item of November 7th,
maybe because the melting process was not for cannon
production. Our research on surface patterns on molten iron
revealed that it requires 0.5% silicon or more for the
hexagonal pattern to appear.10) Also even hyper-eutectic
cast iron with a high carbon content does not form thehexagonal pattern, when the amount of silicon in the iron islower than 0.5%. Therefore, it is quite likely that silicon
was contained in kikko pig iron. It cannot be a coincidence
that the name kikko stands for both the pattern on molten
cast iron of high quality (Fig. 22) and the kind of pig iron in
the Casting Diary owned by the Egawa family. The
description of the firing test on the third 18 pounder, cast on
February 22nd using pig iron, means at least one cast-ironcannon was finished in Nirayama. However, quantity of the
gunpowder used here was probably about half the usual
quantity, as it was only a test. To summarize, a firing test
was run on at least one cannon. According to the Casting
Diary, the riser (*13) was cut off on the last day (30th) of
February and a firing test was run on March 13th. The
record means it took less than 15 days to machine the third
18 pounder. On the other hand, for the first 18 pounder,
machining continued for 73 days, starting on December 4th
and ending on February 17th. Probably the casting partly
got chilled because it was made without kikko pig iron, of
which following describes.
Saga domain is believed to have succeeded in producing
cannons by using ballast (*14) of the Denryumaru theybought from the Netherlands. Ballast is the cast-iron (pigiron) pieces used to weight down sailing ships with tallmasts and keep their balance. In leaving Europe they wereplaced at the bottom of a ship, and in leaving Japan cargos
were loaded instead of them.

Kikko
pig
iron

Fig. 22 Kikko pattern seen on surface of molten castiron of high quality

Fig. 21 Casting Diary of November 7th, 1875
(owned by the Egawa family)
Kikko pig iron was described to be used.

(One kind of Marangoni convection which occurs
due to differences in surface tension)

CannonBallast(a) Microstructure ofcannon(b) Microstructure of ballast

Fig. 23 Compositions of cannon and ballast (*14) loaded on ship wrecked near coast of Australia in 177011)*12 Kikko pig iron: Material recorded in Casting Diary owned by the Egawa family. As the name agrees with that of kikko
pattern mentioned above, it is thought to be pig iron which forms kikko, that is, hexagonal surface pattern (which looks likethe pattern of a turtle shell), when melted. The third 18 pounder made of this pig iron was machined and endured a firing test.
12

*13 Riser: If molten metal is poured in the same volume as a product, cavities form on the surface or inside of the casting,because molten metal shrinks largely as it solidifies. To prevent this, molten metal needs to be kept in a pool (riser) built
above and linked to the part which potentially cavitates. As solidification proceeds, the product part shrinks and runs short ofmolten metal, which a riser is designed to supply to. In cannon casting at Nirayama, a riser was used.
*14 Ballast: as ships in those days were basically sailing ships, iron pieces were loaded at the bottom of them. Some insist
Saga domain cast cannons from the ballast which had been loaded on the Denryumaru, the ship they purchased from theNetherlands. However, it seems unusual to use pig iron with high silicon (Si) content for ballast, as you can see from theorigin of the word ballast, deprived from “bare,” implicating its ”worthlessness.” In addition, the small amount of the
Denryumaru’s ballast contradicts the large number of the cannons they produced.
3.3 Yasujiro Masuda’s Method to Create Non-chilled
Cast Iron without Silicon
There is evidence that a technology existed in Edo era tocreate machinable cannons without generating chill even if
silicon content was insufficient. The cannon Anori shrine
exhibits is said to have been made in the closing days of theTokugawa regime by a founder, Yasujiro Masuda. Fig. 24 is
the pictures of its figure and microstructure. This cast ironcontains a high amount of carbon, which makes its
composition hyper-eutectic. Increasing the carbon content up
to 4.5% enables to create non-chilled casting. Founders inthose days knew that, though most of present-day casting
engineers do not. In the microstructure, you can see roughand large graphite, kish, which directly crystallizes from themolten metal.

According to the overseas literature on this ballast in 1980,
as shown in Fig. 23, the silicon content of the cannon loadedon the ship, (also known as the famous Captain Cook’s11)), is
0.5% and is flake graphite cast iron. The silicon content of
the ballast of this ship is small as 0.01%, and the ballast’s
microstructure is chill12). There is a pronounced difference
between the iron material for cannon casting and that for
ballast.
As for Namban iron, which is thought to have been used
as often as ballast, it is analyzed by Kenji Sato in the Tokyo
Metropolitan Industrial Technology Research Institute13).
Table 4 shows the result, each type of Namban iron has low
silicon levels.
Many point out that the view of Saga domain’s using
ballast contradicts the fact that they produced a large numberof cast-iron cannons.14) Few of these cannons remain today,in addition, which could entail their use of hyper-eutectic
cast iron, as following describes. Therefore, it can be said
that hyper-eutectic cast iron is a leading theory.
Table 4 Chemical Composition of Namban iron, %13)
C
Si
Mn
P
S
1.6
0.08
0.00
0.07
0.00
Oval
0
0
9
6
3
1.5
0.01
0.01
0.01
trace
Thin bar a8671
Surface of
0.4
0.03
0.03
0.00
trace
9
8
7
2
thin bar b
Left side of
0.0
0.07
0.10
trace
trace
thick bar
60
1Considering from the facts, Saga domain had to use pig
iron from a blast furnace in order to obtain high silicon pig
iron. Huguenin’s book on cannon casting clearly describesthat pig iron from a blast furnace should be melted in areverberatory furnace. Apparently people in those days were
well aware of the necessity of blast-furnace pig iron. In thereverberatory furnace diary “the same cannon as the Western
one can be made with the pig iron of the Nagasaki’s pig iron.
However…” Such description shows that they knew it very
well. If that is the case, it is the greatest mystery what kindof metal kikko pig iron was.
Since 1859, bronze became main material for cannons.
One of the reasons of this trend was because the cannons
with a rifled barrel which used streamlined rocket-typebullets replaced the old cannons which used spherical bullets,
as time passes.
13

Kish graphite

200μｍ

C4.48%-Si0.13%-Mn<0.001%-P0.117%S0.034%- Ti0.005% (made by Yasujiro Masuda)
Fig. 24 Cast-iron cannon of Anori shrine and its
microstructure (offered by Prof. Nakae)

Fig. 25 shows the result of our experiment. We examined
the temperatures at which they finish solidification. Black
dots stand for modern machinable cast iron with a highsilicon content. White dots stand for chilled cast iron madeby adding the element of tellurium (Te) into the former

molten cast iron. We compared how the temperature (offinishing solidification) changes depending on the amount ofcarbon contained in each metal. With carbon content of morethan 4.3%, cast iron does not generate chill and turns tomachinable cast iron like that of present day. 15)

because rough and large flake graphite (kish in Fig. 24)
crystallizes in such hyper-eutectic compositions. Examining
the compositions of these Japanese old products reveals it
was common knowledge that cast iron needed to be hypereutectic to prevent it from getting chilled.
According to Ohashi, Yasujiro Masuda, who had made thecannon of Anori shrine, became a millionaire, by producing
213 cannons and 41,323 cannonballs.16) He is also known tohave been highly trusted by Shuhan Takashima. It is highly
possible that his method of hyper-eutectic cast iron was
adopted to produce cannons at Saga domain and Nirayama.
Fig. 26 shows the temperatures at which iron containing
carbon starts to solidify. The temperature decreases as themolten metal has a higher carbon level. When carbon content
is 4.3%, the solidification start temperature goes down to1153°C. From the fact that the compositions of Japanesecastings from the seventeenth to eighteenth century were
nearly eutectic, we can infer that they knew the metal melts
at low temperature when its composition is hyper-eutectic.
Also the existence of non-chilled castings with carbon ofover 4.3% may have been recognized. Mixing with tin
lowers the solidification point of molten copper, which
results in decreasing the melting temperature. By
maintaining the temperature of iron after melting at 1250°C,
about 100°C higher than 1153°C, and adding carbon to cover
the surface of the molten iron, the carbon content
spontaneously increases up to 4.5%, according to thesolubility of graphite. In the circumstances difficult toacquire silicon, this was the only way to make machinable
cast iron.

Fig. 25 Carbon content and chill casting15)

In molten metal whose composition is hyper-eutectic (*15),
graphite crystallizes out first as its temperature decreases.
These graphite particles become nucleuses for flake graphite
to grow from, which prevents the cast iron from getting
chilled. On the other hand, the molten metal with less than
4.3% carbon turns into chill casting because iron itself
crystallizes out first as the molten metal solidifies (the crystal
is called primary austenite in technical terms). Table 5 shows
the compositions of cast-iron castings made between 1590
and 1840 in Japan. Foreign-made castings in the table are
made from non-chilled cast iron, which have a higher silicon
content than those made in Japan. As for Japanese cast iron,
their compositions are mostly near hyper-eutectic containing
much carbon, whereas silicon content is less than 0.1%. Of
such castings, those with over 4.3% carbon are machinable,

Table 5 Compositions of cast-iron
No. Casting item

1

Garden lantern withbamboos and tiger
pattern

Year ofmanufacture

Area ofmanufacture

1591

Chemical compositions, %Kind of cast ironFurnace

0.020

Rough and large graphite cast ironof hyper-eutectic composition (*6)

Koshiki

C

Si

Mn

P

S

Kyoto

4.35
~
4.47

0.05
~
0.06

-

0.23
~
0.24

2

Tea kettle

1600s

Kyoto

4.30

0.03

0.002

0.204

0.027

Chill casting

Koshiki

3

Tea kettle

1700s

Kyoto

4.17

0.07

0.014

0.191

0.019

Chill casting

Koshiki

4

Tea kettle

1800s

Kyoto

4.30

0.04

0.025

0.279

0.020

Chill casting

Koshiki

0.240

0.025

Rough and large graphite cast ironof hyper-eutectic composition

Koshiki

5

Torii gateway

Refe
renc
e

IRON BRIDGE
Cannon (Tokyo)

1839

Nara

4.57

0.05

0.006

1779

UK

3.25

1.48

1.05

0.54

0.037

Machinable cast iron

CupolaAbout 1820

America

3.22

0.69

0.27

0.275

0.132

Machinable cast iron

Cupola?

*15 Hyper-eutectic cast iron is cast iron whose carbon content is over 4.3%. Such iron does not get chilled because carbon works as theseeds which graphite grows from. On the other hand, cast iron with carbon content of less than 4.3% is called hypo-eutectic cast iron.
Without silicon, hypo-eutectic cast iron gets chilled. When cast iron contains carbon of 4.3%, it is called eutectic cast iron.

14

Compared to the old cast iron (with 0.05% silicon) shownin Table 5, silicon content in the composition of Masuda’scannon is a little higher, 0.13%. As for Nirayama
reverberatory furnace, as mentioned above, 23% of thematerials for the third 18 pounder is kikko pig iron.
Regarding the silicon content of kikko pig iron as 0.5%
which is the sufficient amount to form kikko pattern, thesilicon content of the 18 pounder is calculated as follows:(0.5% x 0.23) + (0.05% x 0.77) = 0.15%. The silicon
content of the 18 pounder comes to 0.15%. This value
almost coincides with that of Masuda’s cannon. It is highly
possible that he knew the existence of kikko pig iron andadopted it in his works.
Fig. 28 is the microstructure of the hyper-eutectic castiron made in our laboratory. Its structure resembles that ofAnori shrine’s cannon. In the structure, you can see flake
carbide similar to Widmannstatten pattern, often found inmeteorites.

Fig. 26 Carbon amount and solidification
temperature(a) C4.31％(b) C4.53％
Fig. 27 Microstructures of cast ironC 4.53%-Si <0.01%-Mn 0.070% -P 0.158%-S 0.040%
Fig. 28 Microstructure of the hyper-eutectic castiron made in our laboratory

Fig. 27 is the microstructures of two kinds of cast ironprepared in different ways: (a) the molten metal of the firstone was prepared in ordinary way (C 4.31%) while (b) the
surface of the molten metal of another was covered withgraphite at a temperature of 1250°C and kept as it was(C4.53%). There is an outstanding difference between thetwo microstructures. However, the tensile strength of this
hyper-eutectic cast iron is only 100MPa, which leaves aquestion if a cannon made from it is actually usable. By theway thin castings made from cast iron with carbon content
of less than 4.5% tend to get chilled, whereas cast iron withcarbon content of more than 4.5% shows rapid decrease instrength. To acquire balance of the two characteristics,
4.5% is the best composition. This carbon content
magically corresponds with that of Masujiro Yasuda. As forthe 24 pounder of Saga domain, it contains only 3.2%
carbon, which can be a good reason for being an imported
one. Actually Ohashi writes in his paper that the cast-iron
24 pounder of Saga domain was made in America. 14)
By the way, the strength of cast iron with carbon content
of 3.2% is 250MPa. Cast-iron cannons produced withJapanese reverberatory furnaces do not remain today,
because they were made of hyper-eutectic cast iron which
had low strength and low impact value. Cannons of suchcompositions quite possibly exploded in actual combat even
if they endured machining and firing tests. In Prof. Nakae’s
investigation either, the existence of a cannon surely madein Japan was not identified. This would support the viewthat these cannons with low strength did not endure combat.

3.4 Melting Time of Reverberatory Furnace
I examined the melting time of the reverberatory furnacefrom the operation record of Saga domain and Nirayama. In
Edo period, they used the temporal hour system. Daytime,from sunrise to sunset, and nighttime, from sunset to sunrise,are divided each into six equal parts. One of the daytime
parts means two hours and 38 minutes on the summer
solstice, whereas it means an hour and 50 minutes on thewinter solstice. The time from the start of melting totapping (when the molten metal is tapped out) is expressedwith 16.7 cm incense sticks in the reverberatory furnace
diary of Nirayama. It comes to seven sticks (about four orfive hours). The melting time was the same as the furnaceof Saga domain. Saga domain wrote the details such as thetime from lighting, and referring to it, the average ofmelting time is as shown in Fig. 29.
Probably, it took three hours to heat whole reverberatory
furnace, and cast iron started melting in two hours aftermaterials were thrown in the furnace. They collected themolten metal for two hours from the start of melting to thestart of tapping, after that, they poured it into the mold. As
the combustion temperature of fuel such as charcoal is low,
it is inferred that it was used to preheat the furnace which
required heat quantity most.

15

First lighting
Put cast-iron(Preheating
materialsof the furnace） About 3
hours

Begin melting
About 2hours

Start tapping
About 2hours

Finish pouring
About 1hour

Total
8 hours

Fig. 29 Melting time of reverberatory furnace （Example of Saga domain）17)

Since it took about an hour from the start of tapping(getting out molten metal) to finish pouring, molten metal
could be considered to come out consecutively like incupolas. From the common sense in casting, the defect suchas cold shut (*16) occurs unless sufficient molten metal iscollected and is poured in a short time. The structure ofreverberatory furnace is suitable for storing molten metal,
so certain quantity of molten metal was collected and waspoured in a short time. When receiving molten metal with aladle, the temperature of molten metal decreases by about
100ºC, so it is difficult to pour with a ladle. We can thinkthat they poured directly into the molds of cannons.
Nevertheless, the height from the pouring platform to thetapping hole is only 3 m, and an 18 pounder is 3.5 m long,so a discrepancy remains. Also, the platform was just aplace for molding, so the question or inference occurs thatthe surrounding area of the platform might have been about
4.5 m deep, longer than the cannon. In the investigation of
the pouring platform in 1988, they did not excavate aroundthe tapping hole of the reverberatory furnace1). It is
indispensable to excavate around the tapping hole in orderto make clear whether they poured molten metal directlyfrom the hole.

(Magnetite which is a kind of relatively high purity ironore). I conducted a test with a focus on the amount ofsilicon. We did melting aiming the target composition ofSaga domain cannon shown in Table 6, and investigated thefollowing relationship: melting temperatures, changes ofmolten metal surface pattern, existence of sparks, anddegree of adhesion of molten metal to the graphite
crucible(*17).
Table 7 shows the change of the molten metal surface
pattern and the degree of adhesion of the molten metal to
the graphite crucible at 1290ºC. The surface pattern can beseen on the molten metal with high silicon, but it cannot beseen on molten metal with low silicon. Moreover, in themolten metal with low silicon, sparks generate rapidly athigh temperature range. At the same time, molten metalswells and is likely to spout out. This phenomenon was
written in the operation record of Saga domain, and there isa description of “sparks and smoke rose much”17) in it. The
hexagonal surface pattern can be seen on molten metal with
0.7% silicon. However, it cannot be seen on molten metal
with 0.05% silicon, and sparks generate.
The molten metal of the Saga domain’s cast iron, whichhas 3.2% carbon and 0.7% silicon, comes to adhere to themixing stick and the graphite crucible at 1290ºC, so about
1350ºC even at low temperature is needed to melt.
Solidification start temperature that is obtained from thecomposition of Saga domain’s cast iron is 1248ºC, so at
1280ºC molten metal was thought to start adhering to themixing stick. Generally, pouring temperature for large
castings is 100ºC higher than solidification starttemperature, so we can consider that 1350ºC is the proper
melting temperature for the composition of Saga domain’s
cast iron. However, Okumura and Ohashi dispute madeobvious that Saga domain’s cannon was made in America,so the prospect temperature 1350 ºC itself has no meaning.
In contrast to this, if carbon of Saga domain’s andNirayama reverberatory furnace’s cast iron were eutectic
composition (4.3% carbon), then the solidification starttemperature would be 1153ºC, so the pouring temperature
would be enough at 1250ºC.

*16 Cold shut: If poured melt’s temperature is too low, theboundary occurs at meeting place of molten metal inside ofmold. This phenomenon is called cold shut.
3.5 Consideration from Melting Test of Nirayama
Reverberatory Furnace
In order to infer the maximum temperature in the furnace,heat analysis including radiation heat has to be conducted.
We have not conducted the heat analysis yet. In here, basedon the composition of Saga domain’s 24 pounder (somepeople say it was made in America), whose cast ironcontains 0.69% silicon, and half-moon plate, whose castiron contains 0.05% silicon, we investigated the differenceof molten metal’s qualities owing to Si existence and themelting temperature for casting cannons. The compositionsof molten metal are shown in Table 6.
Osaka pig iron that was recognized as poor quality andused in Nirayama reverberatory furnace is thought to bemade from pig iron of Sanin Iwami. Edo pig iron (alsocalled soft iron) that was evaluated as a little better quality
is thought to be made from rock iron of Kamaishi

Table 6 Molten metal composition used in test17)

Saga domain’s 24 pounder
A little silicon

C
3.22
3.20

Si
0.69
0.05
16

Mn
0.27
0.30

P
0.27
0.27

S
0.13
0.13

Ti
0.01
0.01

Cu
<0.01
<0.01

*17 Graphite crucible: A fire-resistant container made of graphite. It is used to melt cast iron, light alloy, and copper alloy.
Table 7 Difference of molten metal surface pattern (*18) depending on silicon content

Silicon 0.05%

Silicon 0.69%

Hexagonal pattern

The film forms
completely at 1290ºC.

The hexagonal molten
metal surface pattern isseen at 1290-1340ºC.

SparksNo pattern

At 1290ºC, sparks’ rapid
generations are seen.

In 1290-1320ºC, somesurface pattern isgenerated, but it is notclear.

The color of molten metal The adhesion of molten
turns orange at 1400ºC.
metal to the graphite
crucible is seen under
1290ºC.

The color of molten metal If molten metal is stirred,turns white at 1400ºC.
then cast iron adheres tothe mixing stick at
1280ºC.

*18 Surface pattern: On molten cast iron, which has over 0.5% silicon and over 0.02% sulfur, made in a cupola or anelectric furnace, surface patterns such as bamboo-leaf type, pine needle type and hexagonal type appear. The people of thepast judged molten metal with hexagonal type to be good and that with bamboo-leaf type to be bad. I do not think that it is acoincidence that there is a similarity between the name “hexagonal pig iron” in the Casting Diary with the hexagonal pattern
type on molten cast iron. This pattern forms are caused by Marangoni convection owing to the difference of surface tension.
investigated by Nirayama high school students18, 19). The
South furnace was built completely before Saga domaincame to help. The North furnace was built with cooperationof Saga Domain. While the south furnace’s structure allows
heat to concentrate on melted materials, the North furnace’s
structure allows heat to concentrate on molten metal.
Judging from the original meaning of a reverberatory
furnace, the heat distribution of the North furnace built later
is ideal.
In addition, the students conducted an experimentcontrolling the flame by bellows, and they have advocated atheory that the bellows were used in Nirayama
reverberatroy furnace.18, 19) We cannot deny the theory
easily because it became clear that a ventilation hole fromthe outside was installed toward the chimney.20)

From the above, the melting temperature of cast iron in
Nirayama reverberatory furnace is thought to be 1350ºC
with composition of cannon made with Saga domain’s
furnace, and as for high carbon cast iron (more than 4.3%
carbon), which was mainstream at that time, the melting
temperature is thought to be 1250ºC. The solidification starttemperature of bronze chips (Cu90%-Sn9%) excavated at
Nirayama reverberatory furnace, which I will mention later,
was 1028ºC, so the required melting temperature is morethan 1120ºC.
3.6 Heat Distribution of Nirayama Reverberatory
FurnaceFig. 30 shows the thermal energy intensity ratios between
the South furnace, whose first operation was held in July,
1857 and the North furnace in November, 1857. It was17

Fig. 30 Comparison of thermal energy intensity ratios between South furnace and North furnace18, 19)

exist anywhere in the drawing. Fig. 32 is a picture of thereverberatory furnace that seems to have been taken aroundthe time when the furnace was handed over to the ministryof military affair in 1872. We can see piping in front of thefurnace. The piping match the drawing of the piping to
produce tar from coke left in the collection of the Egawa
family (Fig. 33). From this picture and the drawing from theEgawas’ collection, we could consider that a tar room wasmade in the aim of producing coke from coal, and tar was
made as by-product of coke production. This tar was used
for Western-style sailing ship, the Toda, which was built
firstly in Japan in 1855. Therefore, a probability that coke
was used as fuel of the reverberatory furnace is high during
the period, since it needs much heat, when cast-ironmaterials started to be melted until pouring was finished.
Because shachidai (stilted building) can be seen in frontof the furnace in the drawing (Fig. 32), some insist thatmolten metal was poured into a mold with a ladle lifted by acrane. It is considered that they turned the water wheel byusing water of a river called Furukawa, and made a holeinside the cannon. As mentioned above, the period it took tomachine the third 18 pounder is thought to have been lessthan 15 days.

3.7 Whole Aspect of Nirayama Reverberatroy Furnace
In Fig. 31, the whole aspect of Nirayama reverberatroy
furnace was drawn in old picture map. You can see thatreverberatory furnace itself was a group of munitions
factories. From the existence of a drying barn, they appear
to have used a type of molds made by baking green sandmolds, whose material is sand mixed with clay and a small
amount of water. Also, koshiki furnace was there, so it isassumed that materials for construction of reverberatory
furnace and melted materials were produced with koshiki
furnace in advance. Depending on the literature, it isdescribed as a koshiki or tatara furnace. Because tatara
furnace is for production of tamahagane (steel), it is notsuitable to make cast iron. Koshiki furnace can produce
high carbon cast iron, so we have to recognize that people
melted materials not with tatara furnace but with koshiki
furnace.

Fig. 31 Site of reverberatroy furnace in old drawing1)

There was a barn to produce tar, so there is no doubt thatpeople had produced coke from coal. There are arguments
regarding use of coke, but the evidences to deny it do not18

3.8 Number of Cannons Cast with Nirayama
Reverberatory Furnace
Although there are various theories about the number ofcannons cast with Nirayama reverberatory furnace, it is notclear enough. The research result in the literature that has ahigher reliability is shown in Table 8. Inferring from thisresult, it is valid to assume that only three cannons weremade from cast iron.
Table 8 Estimated number of cast iron cannons
produced at Nirayama reverberatory furnace
ReferenceContents
Number ofcannonThe operation record of 18 pounders were
3 cast-iron 18
Nirayama reverberatory produced with castpounders were
furnace etc.1, p.23)
iron. The first one
cast. More than
was machined. The
3 bronze
third one wascannons, andmachined, and its
firing tests were
firing test was
conducted on
conducted. 4 bronze one cast-iron
80 pounders, a 24
cannon.
pounder, total 5cannons.
Catalog of the army
Finished cannons: 14 Materials aremagistrate in 18661, p.23) Incompleted: 50
unclear.
Defective: 36
Purchasedcannon might be
included.
Investigation book on Planned to cast, and However, thethe number of cannons1, sent to Odaiba,
number is
p.20)
Shinagawa, 86
unknown
cannons frombecause it was
Nirayama, 50 fromonly a plan.
Saga domain, 175
from Yushima
Sakuranobaba cannon
factory, and 5 from
Osaka.
The Shimazu family
Ten 80 pounders, two 28 cannons.
investigation, Weapons 24 pounders, twelve
and reverberatory
12 pounders, and 4
furnaces of eachlong howitzers, total
domain1, p.21)
28 cannons weremade at Nirayama
reverberatory furnace,
were sent to No.1
Odaiba.
Masao Serizawa:
Trial casting 5times, 3 3 cast-iron 18
Yoshiki Seitetsu notimes cast 18 pound in pounders, 128
Hoga21, p.94)
two furnaces
bronze cannons
combined. From 1863 (100 of themto 1864, 128 bronze were defective).
cannons were
produced and 100
cannons became
defect.
Kurao Kubota; Material 75 cast iron cannon
12 cannons
Science andwere produced, and succeededTechnology22, p.67)
12 cannons had noamong 75
defects such as cavity cannons.
shrinkage.

Tar
Distillation
pipingFig. 32 Nirayama reverberatroy furnace in about 1872
(Meiji era) (owned by the Egawa family)

Fig. 33 Tar distillation piping to produce coke from coal(owned by the Egawa family)

Bronze chips were found at the excavation in 2013, andthe result was shown in Fig. 34. This chip is made fromonly copper and tin, and lead was not included. The ratio oftin is about 10%, and it matches the description in thereverberatory furnace diary of Nirayama that they bought
copper 2700 kg and tin 270 kg. From this chip, we canpredict that cannon had been cast with bronze whose
solidification start temperature is approximately 1020ºC,
and been machined as described in the reverberatory
furnace diary. The total bronze cannons produced at
Nirayama is estimated to be four 80 pounders and one 24
pounder from the diary.

Chip just after excavation
Cu：89.7%
Sn：9.20%

Chip after cleaning
Pb undetected

Fig. 34 Bronze chip found at excavation of Nirayama
reverberatroy furnace

19

One of the three was cast with high-quality pig iron
whose melted surface pattern is hexagonal one and which iscalled hexagon pig iron (kikko pig iron). After machining, itmaybe had a firing test.

graphite parts had silicon as high as 0.17%, and carbon was
4.32% that is hypereutectic composition. Interfaces of graycast iron and chilled cast iron were rough, and then it isassumed that the balls were made from the composite
material made by pouring two kinds of molten metal having
different compositions. Cannonballs are hollow inside, so it
is an interesting mystery how to prevent separation of those
two kinds of components, owing to gravity.
By the way, the maximum flying range of 24 ponder was
2793 m, and that of 18 ponder was 2600 m. The flying
distance of the bronze 20 duim mortar, which is located at
Nirayama reverberatory furnace, was 1364 m surprisingly,
with 469 g of gunpowder.

3.9 Cannonball Used in a Firing Test in Hagi
Cannonball used in a firing test in Hagi and its
microstructures are shown in Fig. 35. This cannonball was
made from a composite material of three kinds of iron. (a)Inside is made of machinable cast iron (flake graphite castiron), (b) outside is made of chilled cast iron, and (c) the
surface is made of whiteheart malleable cast iron (steel) thatis made by heat-treated chilled cast iron. Also, flake(a) Cast iron
鋳鉄(b)
チChill(c)ルMalleable
可鍛鋳
cast iron
鉄
43t
White parton inside (a) of cannonball made of gray cast
内側白色部の鋳鉄
ironSurface (c) of malleable castiron

Chill microstructure on outside (b) of cannonball

C

Si

Mn

P

S

Composition range of the Hagi cannonball

3.7～4.3

0.0015～0.16―

0.05～0.16

0.05～0.14

Flake graphite part

4.32

0.17

＜0.005

0.15

0.018

Fig. 35 Microstructure of the cannonball which was shot as a trial at Hagi (Offered by Professor Nakata
Takeshi of Shibaura Institute of Technology)

20

Namban iron and ballast of ships are considered as agood melted material, but according to this investigation,
they were chilled cast iron. At that time, people bought
cast-iron cannons from abroad, so there is a high possibility
that existing cannons which contain 3.2% carbon and about
0.5% silicon are imported cannons. It was after blast
furnaces’ invention that they could get high silicon andcould produce cast-iron cannons of low carbon and of highmachinability.
I hope that this paper will help in “Sites of Japan’s Meiji
Industrial Revolution: Kyushu-Yamaguchi and related
Areas” including Nirayama reverberatory furnace as World
Industrial Heritage Site.Moreover, I would really appreciate
it if many people would get interested in foundry
engineering.

Conclusion
Although I could not explain about all items (mysteriesof Nirayama reverberatory furnace) due to limitations ofspace, Table 9 summarizes the mysteries.
It is difficult to conclude that cast iron had not been
melted in Nirayama reverberatory furnace, if we guess fromthe reverberatory furnace diary. According to the diary, it isappropriate to think that three cannons were produced fromcast iron, and one of those cannons had a firing test. In
order to make non-chilled cast iron (machinable cast iron),the possible way is as follows: (a) set the quantity of kikko
pig iron with about 0.5% silicon at 23% of the totalmaterials, which makes the molten iron contain 0.15%
silicon. (b) Spread carbon over the molten iron of just its
carbon content to 4.5%. This temperature, 1250ºC, is low
enough to prepare in Nirayama reverberatory furnace.

Table 9 Conclusion of mysteries remained in Nirayama reverberatory furnace

Remained mystery
1. Was cast iron melted with Nirayama
reverberatory furnace?
2. How high was the melting temperature?

How to melt

3. How long did it take to melt materials?
4. Was metal poured directly into a mold, or
into a ladle (*8) before pouring?
5. Were bellows used?
6. What was the fuel? Was coke used?

OthersBricks7. What kind of materials were used, iron sandfrom Iawami, gantetsu (iron ore) from Iwate,
imported pig iron (Namban iron), or ballast?

Conclusion
Pouring temperature was about 1250 ºC with about 4.5% carbon
content same as that of the cannon of Anori shrine. It was madeby Yasujiro Masuda who was a founder in Kawaguchi.
About eight hours from first lighting to completion of pouring.
Though casting time was written as an hour, it was conceivablethat certain quantity of molten metal was collected and waspoured in a short time.
The molten metal seems to have been poured directly into the
upright cannon mold. Neither a ladle nor a crane was used.
There is a possibility that they were used to control the flame.
Coke was used.
It is said that Saga domain used ballast and increased content ofsilicon, but there is a possibility that ballast did not containsilicon. Kikko pig iron (high-quality pig iron) which probably
included high silicon (about 0.5%) was used in the third cannon at
Nirayama. “Where people could get Kikko pig iron from”
becomes a next mystery.

8. Where were the bricks forming the furnace
fired?

Bricks marked with a circle were made in Kawazu Nashimoto,and those without a circle were made at the back hill of
Nirayama. Bricks were fireproof brick made with burned white
alumina clay.

9. How many cannons were produced, andfinished at Nirayama?

Four iron cannons were cast, and two of them had firing tests.
Four 80 pounders and one 24 pounder were made of bronze.

10. Defects caused by compositions of cast ironcannons

The main reason is that people could not get the melting materials
with high silicon contents. Therefore people cast hyper-eutectic
molten metal whose carbon contents was more than 4.3% and did
not get to chilled same as the cannon of Anori shrine. It was madeby Yasujiro Masuda who was a founder in Kawaguchi. If thecannon was hyper-eutectic, the cannon could be machined andhad a firing test that needs half of powder. However, thosecannons had a high possibility to have exploded in actual combat
because of low strength and low impact value. That’s the reason
why no cannon exist in Saga and Nirayama.

* According to the latest research, it is found that four iron cannons were cast (not three) and had firing tests.
21

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Hakubutsukan Chosakenkyuusho 5 (1979) 34, 39
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22