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Friday, 8 October 2010

Hot Process Soap Making

Photographs and process courtesy of Elizabeth at Gracefruit. Where you can find more recipes and loads of great ingredients too.


Firstly because the sodium hydroxide or lye is 'cooked' during the hot process soap making, it neutralises itself much quicker than when making cold process soap. This means, in theory anyway, you can use the soap sooner... (I do find it best to leave the soap to cure for the same amount of time but it isn't strictly necessary...just my way of doing it).

Secondly... any volatile or delicate ingredients that you may add, such as essential oils or superfat oils - are added after saponification, so they are not so much affected by the sodium hydroxide.

The method requires the use of a crock pot for ease... and peace of mind... but you can do this in a double boiler too... and I know some people do it in the oven.

Just like cold process soap you melt your oils and you add the lye. Unlike cold process soap you don't have to wait for the lye to cool down... as soon as it is disolved you pop it in and give it a stir with the stick blender.

You stir it until it reaches a good thick trace don't know what that is? You need to read about making cold process soap first.

As soon as you have reached a good thick trace put the lid on the crock pot and set it to low. Then you leave it for about 30 minutes. During this time the edges of the soap (or where the pot is hottest) will begin to gel.

Keeping checking back every ten minutes or so and you will see that more and more of the soap is gelling. Until..

all the soap in the crock pot has gelled. At this point you need to remove the crock pot from the source of heat and stir to make sure that all the soap has gelled. Then you can take a small amount of the hot soap (ouch!!) out and rub it between your fingers it should feel waxy as it cools.

Now comes the bit I never do (well I did it once and didn't like it!)

The Zap Test.

This involves touching the cool soap to your tongue and if it Zaps you... i.e. if it feels like you touched your tongue with a battery then there is uncooked lye in the soap and you need to pop it back on to the heat to cook a little more.

If the soap feels fine on your tongue then its time to add fragrance and colour and anything else you fancy!

Here you can see that Elizabeth is adding some jojoba oil. Because the soap has already saponified this oil will remain as 'free oil' in the bar - which has to be nice on your skin...

Then she has removed some of the soap and coloured it green. She then adds it back into the pot and gives it a swirl.

The lightly swirled soap gets put into a mould and left to cool overnight just the same as you would with a cold process soap.

In the morning you can unmould your soap and put it somewhere to cure. As I said... curing time is cut down by this method of soapmaking but I like my bars nice and hard so I do tend to leave them the full four weeks anyway. Doesn't it look great? I wonder what it smells like?


You may notice that the texture is not as fine as that of cold process soap (although Elizabeth has done an excellent job). Sometimes I think I used to overcook mine and it was very much like mashed potato. I should think practice is needed to get a really good finished look like these. Isn't that half the fun of it though?

Also... of course it is not as eco-friendly as cold process soap. If your electricity or gas bill is of concern (as is the future of the planet) then you may decide that this method is not for you.


  1. By the way... you can use any normal cold process soap making recipe for this. Just follow these instructions instead of the cold process ones.

  2. Great info! the best site I've come across in my many weeks of reading up soap stuff.
    I've come to know that a soap can't be really called organic bec of its lye %, but to get a foot into soap business and if I have used food grade organic ingredients, what do I call my soap?? when everybody around call theirs organic!

    1. after reacting with alkali when the soap is formed, there is no longer any lye but only soap and glycerol :)

    2. Organic is just a word. And its definition is not actually dictionary defined. As Tanishq has said, once your soap is finished, it does not contain any lye, therefore I do not see any problem in calling the soap organic. But ultimately it is down to you, if you don't want to use the organic word you can always describe your soap differently...


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