From: kelso@eng.umd.edu (John Kelso)
Subject: Soap making, procedure & theory (long)
Date: Sun, 22 Nov 92 15:35:41 GMT
Organization: University of Maryland, College Park
Keywords: soap


I first got interested in making soap when I read a posting in rec.food.veg
about making soap using vegetable oils, as opposed to using commercial
soaps which are made mostly of beef tallow.  I've always enjoyed making
things, and soap seemed to be easy to make from the recipe that was given.
I also thought that if I was successful, I could use my soap as fun little
give-aways for friends.

Although my first batch of soap was a success, I wasn't content.  I wanted
to learn how to make different kinds of soap; this led me to do a little
research.  I first looked for books on soapmaking in my local libraries and
bookstores.  There are more of them that you might imagine, and they vary
drasticly in quality.  The best one I've found so far is _Soap: Making it,
Enjoying it, Using it_, by Ann Bramson, from the Workman Publishing Co.
The process I describe, and some of the recipes, come from her book.  Get
it.

A more technical reference was found in the University library: _The Modern
Soap and Detergent Industry_ by Geoffrey Martin, 1931.  Also useful was the
CRC Handbook of Biochemistry and Molecular Biology.

From what I read, soap and glycerine is created when oils are mixed with a
caustic solution.  Soap factories use the "hot process" to create soap.
This process can create a harder soap from lower quality ingredients.  Soap
factories also remove the glycerine that is created, as it is a valuable
substance used in other products.  But, when the glycerine is removed, the
soap will attract water, and thus be used up faster.  Soap that is made at
home uses the "cold process".  The glycerine is not removed, resulting in a
longer-lasting bar of soap.  Also, the glycerine is soothing to the skin.

Different oils and fats can be used in making soap.  The different oils
have different properties, and produce different kinds of soap.  The
chemical process of turning oils into soap is called saponification.

The caustic solution is made from water and potassium hydroxide (KOH) or
sodium hydroxide (NaOH).  Solid soap is made using NaOH.  NaOH is also
called caustic soda, or lye.  All the recipes will be using lye.  Lye can
be bought at most hardware stores as a drain cleaner.  Red Devil is one of
the more common brands.  Lye usually comes in 12 oz cans, so that is how
much is used in the recipes I give.  Liquid soap is made using KOH.  The
two substances differ in their ability to saponify oils- the ratio is 56.1
parts KOH equals 40 parts NaOH.

The basic soapmaking process (mostly taken from Bramson):

required: a jar with a perforated lid, a thermometer, a scale, a large
mixing bowl, a large wooden or plastic spoon, flexible molds, oil, lye
water, mineral oil.

ALL measurements, even the water, are in ounces- not fluid ounces, but
ounces as measured on your scale.

1) Mix a solution of lye and water.  BE VERY CAREFUL WITH LYE!  DON'T TOUCH
IT!  DON'T SPILL IT!  Wear goggles and gloves.  Mix 12 oz of lye in to a
jar filled with 32 oz of water.  It will get very hot, and produce nasty
fumes.  Do it outside if possible.  Have the jar in a bucket in case of
spills or breakage.  Do this several hours before you want to start making
soap, as it needs time to cool.

2) Heat and mix your oils in the large bowl to between 95 and 98 degrees.
Bring the lye solution to the same temperature.  Hot water baths are a easy
way to do this.

3) While stirring the oil, pour the lye solution through the perforated lid
into the oil.  Wear your gloves in case of drips.  (The perforated lid
keeps the solution coming out at a slow steady stream.)  Keep stirring.  It
will gradually thicken.  This may take anywhere from 15 minutes to 90
minutes.  You may have to immerse the bowl in hot water to keep it warm
after an hour or so.

4) Add any color or scent.

5) Pour the soap into the mold(s), which have been rubbed with mineral oil
to keep the soap from sticking.  I use a large Rubbermaid lasagne pan sized
container.

6) Wrap the mold(s) with blankets and pillows to retain the warmth.  The soap
will continue to saponify.  Let sit for a day.

7) Pop the soap from the mold(s), and cut into bars.  Stack them up so that
air can circulate, and let then age for a couple of weeks.

8) Carve them up and make them pretty.

------------------------------------------------------------------------

I've made soap using Crisco, coconut oil, red palm oil, olive oil, etc.
I've never made it with lard or tallow, but I'm told its easier.

I get coconut and palm oil at indian and Caribbean groceries.  Try Walnut
Acres for mail order.

Weigh the lye- the amount on the can isn't always accurate.

For a mold I use a tupperware container that's been greased with mineral oil.
It's about the size of a lasgna pan, and big enought to hold the whole batch.

Making up your own soap recipes is easy if you can do some simple
algebra.

The key value you need to know for the oil you want to use is its
saponification value:

It's expresed as:
x mg of KOH saponify 1 g (1000 mg) of oil

This is used when you have a fixed amount of lye, and want to know how much
oil to use.

A related measure is the saponification equivalent:
x parts by weight of oil are saponified by 40 parts NaOH
ex: a saponification equivalent of 285 means that you need
285 g of oil to "use up" 40 g of NaOH.

This is used when you have a fixed amount of oil, and want to know how much
lye to use.

The fraction of NaOH absorbed:
This is used when you want to easily compute ratios of oil to lye, and is
all you really need to know.  Here's how it's derived:

fraction = sap. value/1405.5

sap. value = 56100/sap. equivalent

sap. equivalent = 56100/sap. value


Here are the values for different oils, as taken
from the Chemical Rubber Handbook: (I computed the fractions)

oil			sap. value	fraction NaOH absorbed
--                      ----------      ----------------------
babassu			247		.175
castor			180.3		.128
cocoa			193.8		.137
coconut			268		.190
coffee-seed		183.7		.130
corn			192		.136
cotton			194.3		.138
kapok			192.6		.137
linseed			190.3		.135
mustard			174		.123
neem			194.5		.138
niger-seed		190		.135
olive			189.7		.134
palm			199.1		.141
palm-kernel		219.9		.156
peanut			192.1		.136
perilla			192		.136
poppy-seed		194		.138
rapeseed		174.7		.124
rice bran		180.1		.128
safflower		192		.136
sesame			187.9		.133
soybean			190.6		.135
sunflower-seed		188.7		.134
tung			193.1		.137
wheat germ		184.7		.131
cod-liver		186		.132
herring			192		.136
menhaden		191		.135
sardine			191		.135
sperm whale, body	122-130		.086 - .092
sperm whale, head	140-144		.099 - .102
baleen whale		195		.138
butterfat		227		.161
human fat		196.2		.139
lard			194.6		.138
neat's foot		190-199		.135 - .141
beef tallow		197		.140
mutton tallow		194		.138


An example: you have 12 oz of lye, and want to mix your oils 75% soy
(shortening) and 25% coconut.

x=amount of coconut oil
3x=amount of soy oil

3x*.135 + x*.190 = 12

x=20.16, so 20.16 oz of coconut oil, 60.50 oz of soy for 12 oz lye.

Different types of oils givedifferent types of soaps:

1) coconut, palm kernel- saponify rapidly at ordinary temperatures.
well suited for cold process soap. coconut produces a firm, high
yielding soap, hard, white and brittle.  coconut dries the skin.

2) olive, cotton seed, corn oil.  consist mostly of olein.  olive
produces a greenish soap called "Castile", with thin slimy lather.
excellent for the skin.  cottonseed oil saponifies with difficulty, and
can become rancid.  corn oil soaps discolor with time.

3) tallow, palm oil, greases.  tallow yields a hard soap with an
inferior but persistent lather, excellent for shaving.  palm oil
produces a soap similar to tallow.  most commercial soaps are a
mixture of tallow and coconut oil.

4) linseed and castor oil.  yield a quick lather.  make a brown soap.

5) red oil and rosin.  red oil os oleic acid.  mostly used with other
oils, like tallow, to improve their characteristics.

6) hardened or hydrogenated oils (Crisco and other shortenings).  produce
harder soaps.  hydrogenated soybean oil can be used as a substitute for
tallow.  adding 5-10% castor oil increases lathering power.

A recipe for white soap using the cold process method from an old book-
I haven't tried this at home. 8^)

Mix 120 lbs of tallow, lard or palm oil with 40 lbs of coconut oil in a
large container.  Heat until 120 degrees.  Gradually add 80 lbs of
caustic soda (30% by weight NaOH).  Don't let the temperature rise
above 122 degrees, otherwise the lye will separate.  Stir diligently.
the saponification will be done in about two hours.  Add perfume and
coloring before it cools.  Put in a covered frame.  Yield is 236 lbs of
white soap, which lathers well due to the coconut oil.

Another recipe for making soap in small quantities, from the same book:

Mix 10 lbs of double refined caustic soda (98% NaOH) with 4.5 gallons
of water.  It will generate much heat.  Let it stand until it cools
off.  Heat 75 lbs of grease or tallow to not over 100 degrees.  (If oil
is used, no heating is required.)  Pour the lye into the fat in a
continuous stream, while stirring.  Continue gently stirring until it
has the consistency of honey- from 15 to 20 minutes is usually
sufficient.  Pour into a large square box- dampen the sides so the soap
will not stick.  Wrap with blankets and leave in a warm place until the
next day.  remove from the frame and cut into blocks.  Yield is 130 lbs
of soap.  If the soap feels sharp, too much lye was used.  If it feels
soft, mild and greasy, too little was used.

-- 
		John Kelso   Manager, Application Services
   University of Maryland College of Engineering, College Park MD 20742
	     kelso@glue.umd.edu -or- uunet!glue.umd.edu!kelso
--
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