How I HP

I have had a few queries about making soap using a Hot Process (HP) rather than the perhaps more frequent Cold Process (CP), so I thought I would walk you through what I do.

But please note – this is what works for me, based on my knowledge, reading and experience – I would make NO claim to it being a “correct method”! 

Also – although I live in Oz and usually think in terms of degrees C for temp, for soap making my thermometer is set to degrees F – mostly because loads of the info that I have learned from is from USA.

Oils and butters are mixed and melted in the crock pot to whatever temp it takes to melt the slowest melting component (usually the shea butter, but beeswax takes the longest and requires the hottest temp), then I hold at that temp or turn the heat off for a bit.  My mixes are using 800-900 gm of oil, and my crockpot is a 5 litre pot.

While the betters are melting, I combine the water component and the lye, and cool it to about 140F or lower.  I aim to get the two pots within 10 degrees (F) of each other, but have discovered (with my HP) it doesn’t that much matter.

I take the ceramic inner pot out of the heated crockpot shell to add the lye / water mix and blend.  I combine the oils and the water/lye at any temp from room temp to about 140F, depends on how many other things I am doing, or how much of a hurry I am in.  I find them quite forgiving.

Because the two components are usually combined fairly hot, “trace” is reached quickly with the stick blender – I never pay much attention to whether it is thick or thin trace – it all works out in the end.

Then the inner crockpot goes back into it’s shell and I turn the heat on “High”.  Depending on our weather (2 weeks ago here, daily max was 20C, but 2 days ago it was 36C), and the temp at which the mix is after blending, I set my timer for 15 or 20 minutes. If the weather is cold, maybe the cook can take 30 minutes.

This is what I am looking for:

The crockpot heats unevenly so the outer edge is well over 180F (the temp at which I understand that saponification occurs), but the centre has not quite got there.

At this stage I am confident that I can “force” the rest of the reaction by whisking, so I remove the ceramic inner part of the pot to the bench again (making sure it sits on something suitable to absorb the heat).

After an initial stir to homogenise the mix, this temp evened out at 189F (for each batch the temp will individually vary), but the consistency looks a bit “chunky” – sometimes it evens looks as if it will separate.

This is where I whisk and watch.  The mix will start to heat up of it’s own accord whilst whisking (remember, the pot is out of the heating container at this stage) – it releases steam and the consistency starts to change – becoming shiny and looking more like a gel.  (It reminds me of seeing the gluten development while kneading bread dough.)  And you can see the temp significantly increase.  I usually add a couple of tablespoons of plain yoghurt at this stage too which seems to help the consistency (this is one of those tips I read somewhere and implemented and it worked, but I can’t remember where I read it).

And then, when the reacting is complete, the texture is thickened and homogenous, and the soap cools down quite quickly.  I keep whisking until it stops changing, and cools down.  The whisking doesn’t take too long, and is strangely satisfying – gives me a real feel for each batch.


This soap has colloidal oatmeal added and kaolin clay – I had taken some of the water component (or in this case chamomile tea), to mix with the clay and oatmeal (otherwise they clump and don’t mix through well).  I should possibly have added a little more of the liquid to this mix.


I wait until the soap has cooled a little before adding these – to stop the oatmeal from cooking to porridge!

And I have the essential oils waiting to go in as well.  These are mixed together with my “superfat” oil from the soap mix – about 20-30gm – in this case Tamanu oil – and the EOs were Lemon Tea tree and Violet leaves 3% in jojoba (usually Chamomile, but I had run out).  I mix them early and allow the scents time to synergise while I make the soap mix.

Then I google the “flash point” of whatever EO I am using and try to cool the soap mix to under this temp before I add the EO mix in order to minimise loss of scent.  This is difficult with citrus oils though as the soap has pretty well hardened before you get low enough not to “pop” the scent.  If you cool to less than about 125F the soap is getting a bit too set to easily push into the mould (it’s possible but it looks uglier).

I try to use something to “anchor” the scent if I use citrus – either another EO like patchouli if I want that scent.  Jojoba and Meadowfoam oils are also supposed to help “hold” the scent of the citrus, so I may use these as a “superfat” oil to blend the EOs in.

I use 1L cardboard milk containers for moulds (I have generous friends who collect them for me).  This means that I have only a small “top” – the rest of the soaps are consistent.  Because I cool the mix for the EOs, it is not as obliging as a CP soap for making a fancy “top” – it acts more like glue!

Send me a message if you have questions!  Like I said at the start this is just my developed and developing method that works for me – happy to hear from you if you have any hints!!

Enjoy your days : )


UPDATE (next day): So the very next batch I made (using my tried and true method – LOL!) looked like a disaster.

I had really rushed it and skimped on the first stick blending – I kind of convinced myself it had got to a light trace, but maybe not…  Then short-changed the cook time – again convinced myself it was hot enough to whisk.  Started whisking and it all looked like oily curds and whey.  Thought I would have to delete this post completely, but my stubborn streak kicked in and I gave it a little stick blend, a bit more whisking, then put back to heat some more.  Ten minutes later – different picture – it was gelling and looking like my normal soap mix.  All good – MORAL OF THE STORY – don’t be put off, HP will usually come through if you persist – it is kind of like an instant rebatch!

And then I thought I should add – I cut the soap after a day, but my soap is often quite soft (due to oil types and water content).  Once cut, it hardens fairly quickly – I usually leave a week or two to dry out, but pH-wise, it is ready to use straight away.


Sarah : )





7 thoughts on “How I HP

  1. Ooooo – I love this post. Thank you – good, clear step-by-step ‘instructions’/ information and the photos help a lot. Also the temp ranges – I think I would have panicked if I’d seen those readings as I’m used to cp and avoiding gel…I am so going to have to give this a go. Thanks again

    Liked by 1 person

  2. Pingback: Hot Process – First Attempt | The Soap Mine

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