The Iowa plain dealer. [volume] (New Oregon, Howard County, Iowa) 1867-1895, 1884-03-13
About Tcrra.COtta.

AAO pOputuI huONieupO VI tcFE0-
Gotta in America may be said to consist
in greater or less familiarity with such
small objects as the statuettes made in
Italy and in Spain illustrative of the
types and costumes of the people, and
in some general information concern
ing the relics of various ages in the
museums and churches Of Europe; but
the capabilities of terra-cotta as ma
terial for practical and arti tic uses are
little appreciated.
1t is our purpose to show not SO much
what has been done in tcrra-cotta rs
what still remains to he done, and how
we can learn from the best examples
to avail ourselves of the advantages
the material offers, especially in cer-
tain classes OF art work. The manu-
facture Of fterra-cotta has been carried on
in some form from the earliest civiliza-
ton of which we have any record: in
fact, much of our knowledge of ancient
history has been derived from terra
Gotta tablets, whose inpervious SUR
faces have retained the original inscrip-
tions for thousands Of years, unaer
conditions that have caused stone to
crumble away and have corrodcd metal
until all trace of its hayiag been fa IL
ioned by human hands has Il ;sappearel |.
Terra Gotta would literally include
everything male of cooked earth, !"
from brick to CHINA and porcelain; but
what is now understood by the term is
something neither so rough and coarse
as brick nor SO fine rs porcelain. 1t is
not an imitation of stone nor substi-
tute for It, but material possessing
distinct advantages and capabilities
subject to the limitations imposed by
the consistency and the processes Of
manufacture. which processes have now
become SO exact as to enable us to de-
fine clearly the advantages and disad-
yantages Of terra-cotta rs compared
with other materials in any particular
undertaking. As an understanding Of
the nature of any material is the first
requisite for its proper treatment in
design, we shall briefly describe the va
rious stages Of manufacture, from the
selection of the clay to it's final crystal
lization in work of art.
The clay selected for terra-cotta is
that composed of silicate of alumina
and small percentage of iron, oxides
of iron, as in bricks, producing red
color when fired. The clay is stacked
in sheds until it is dry; it is then
ground to fine powder, and mixed with
powdered old terra-cotta or with ground
flint, granite sand, or other yitritiable
| substances. The mixture is then
ground with certain small proportion
of water, to obtain perfectly homo
geneous, ductile modelling clay free
from the smallest air cavities. The
proportion Of water determines the
shrinkage that must occur in burning,
and this shrinkage can be relied upon
rs one-twelfth.
All objects, whether mere cubes OIL
statues, must be hollow, and as nearly
rs possible Of the same thickness
throughout, as solid object invariably
becomes distorted in burning. owing to
the interior being more slowly baked
| than the exposed portions. The darker
/ the color required, the harder the firing
must be, often reaching white heat,
or more than HOO deg L.
| 1t has not always been possible to
attain perfect uniformity of color III q
number Of pieces of terra-cotta, even
same mixture and burned at the same
time; bnt this fact is rarely serious
/ objection. On the contrary, in man,
instances some variation in tone i'll {
monotonous redu, LEGATION OF form i.
agreeably effective. +. Oakley, IN
! Harper's Nagazi,le.