Soapmaking
Practical Action
At this stage the mixture should be uniform with the consistency of cream. A few drops
cooled on a glass plate should show neither separate globules of oil or water droplets.
Continue boiling and add the remainder of the fat and lye alternately, taking care that there is
no excess lye at the end of the process. Boiled hard soaps have saponified when the mixture
is thick and ropy and slides off the paddle.
Up to this point, the process is similar to boiling soft soap, but the important difference in
making hard soap is the addition of salt at this point. This is the means by which the creamy
emulsion of oils and lye is broken up. The salt has a stronger affinity for water than it has for
soap, and it therefore takes the water and causes the soap to separate. The soap then rises to
the surface of the lye in granules and looks like milk curd. The spent lye contains glycerine,
salt and other impurities, but no fat or alkali. Pour the honey-thick mixture into soap moulds
or shallow wooden boxes, over which loose pieces of cloth have been placed to stop the soap
from sticking. Alternatively, the soap may be poured into a tub which has been soaked
overnight in water, to cool and solidify. Do not use an aluminium container because the soap
will corrode it. Cover the moulds or tub with sacks to keep the heat in, and let it set for 2 - 3
days.
When cold the soap may be cut into smaller bars with a smooth, hard cord or a fine wire. It is
possible to use a knife, but care is needed because it chips the soap. Stack the bars loosely
on slatted wooden shelves in a cool, dry place and leave them for at least 3 weeks to season
and become thoroughly dry and hard.
Be careful! Uncured or 'green' soap is caustic since the lye has not reacted fully with the fat
and neutralised it. This is known as the curing process. Wear rubber gloves when handling
the hardened soap until it has been cured for a few weeks.
Difficulties involved with the soapmaking process
Problems that can occur in soapmaking and their possible causes are described in Table 2 :
Problem
Soap will not thicken quickly
enough
Mixture curdles while stirring
Mixture sets too quickly, while in
the kettle
Mixture is grainy
Layer of oil forms on soap as it
cools
Clear liquid in soap when it is cut
Soft spongy soap
Hard brittle soap
Soap smells rancid
Air bubbles in soap
Mottled soap
Soap separates in mould, greasy
surface layer on soap
White powder on cured soap
Warped bars
Possible causes
Not enough lye, too much water, temperature too low, not
stirred enough or too slowly, too much unsaturated oil (e.g.
sunflower or safflower).
Fat and/or lye at too high temperature, not stirred enough or
too slowly.
Fat and lye temperatures too high.
Fat and lye temperature too hot or too cold, not stirred enough
or too slowly.
Too much fat in recipe or not enough lye.
Too much lye in recipe, not stirred enough or too slowly.
Not enough lye, too much water, or too much unsaturated oil
Too much lye
Poor quality fat, too much fat or not enough lye.
Stirred too long
Not stirred enough or too slowly or temperature fluctuations
during curing.
Not enough lye, not boiled for long enough, not stirred enough
or too slowly
Hard water, lye not dissolved properly, reaction with air.
Drying conditions variable.
4