Oven Hot Process Soap Tutorial

by Adrienne Gidley

For an explanation of the different soap making methods discussed in this article, we recommend reading the Teach Soap article, "Soap Making Methods".

I started out doing cold process soap (CP), and I still love that way of making soap. You really can achieve a higher level of artistry with cold process. CP has become easier than ever since some clever soapers started discounting water, soaping with room temperature oils, and of course using a stick blender. It’s nice to be able to blend your ingredients, pour into a mold, cover it, and leave it to sit until it’s ready to cut. Hot process (HP) is not, in my opinion, easier than CP. But it’s more interactive…and I like interactive. I’m what you’d call an “anxious soaper;” meaning I hover over the soap as much as I can, peek under the lid, poke it with a thermometer, and in general bother the heck out of it. There’s only so much you can do to cold process, but with hot process, bothering the soap is not only encouraged, but a necessity!

Anyway, another one of the benefits of hot process soaping is being able to reduce your fragrance amount—yes, you really can reduce the amount you use by half! The fragrance is also less likely to morph. I’ve heard that another benefit of hot process is that your soap won’t do funky things when you add the fragrance…I don’t think this is entirely true, though. Most of the time, when I add the fragrance, the consistency of the soap changes. It thickens appreciably. Some fragrances don’t do this; for example, Scent-Works lilac doesn’t, Soap Studio's Fresh Lemon doesn't, and most essential oils don't.

I read several tutorials before I attempted hot process, and then adjusted them to suit my own methods. I think the key ingredient to achieving a look similar to cold process is the addition of sodium lactate (SL). It really helps the soap stay fluid. Also, it is imperative that you not discount your water. Use the full recommended amount (such as the one recommended by an online lye calculator).

I don't deduct the amount of water by the amount of sodium lactate (SL) I add. I add the full recommended water amount, plus .25 oz of sodium lactate (SL) parts per ounce (ppo). I know the recommended amounts for SL are .5 to 1 oz ppo, but I like the consistency of the soap better with less than that. It's less crumbly.

Alright, on to the pictures! Ok, I set the dial on my oven to 210º...I set it that high because my oven is old, and I don't think the dial is an accurate indicator of temperature. I first tried setting the dial to 170º, but the soap took 30 minutes to reach a thick trace! It never even cooked or gelled! I recommend starting lower, and then adjusting the oven temperature as needed.

I weigh and combine my ingredients in a smallish stockpot, and I make sure that the Palm Kernel Oil (and cocoa butter, if I'm using it) are broken into small chunks. I add my hot lye water WITH sodium lactate & stick blend to trace. I also make sure that there are no chunks in the traced soap. They would probably melt during the cook, but I don't want to chance it.

Here I am stickblending the soap to trace. You can cut your oven time by stickblending the soap as much as possible, until it’s at a thick, blobby trace, but I prefer not to tax my stick blender unnecessarily. Might as well let the oven do the work for you—especially if you’ve got lard in the soap—your wrist will thank you. Depending on your colorant/additives, you can add them at trace. I used select shades for this batch, and since the color is liquid, I added it at trace so that the color would be well incorporated. I added 1-2 tsp of aquamarine, if you must know.

I put the stockpot with the lid over it in the oven and set the timer for 15 minutes. After 15 minutes, the soap should either be at a gloppy trace or firming up to the consistency of cookie dough. Go ahead and take it out and stir it.

This is what it looks like after 15 minutes in the oven. It doesn’t look much different than it did 15 minutes ago, but I like to check it anyway. Put it back in the oven for another 15 minutes. You could probably just set the timer for 30 minutes and skip this step, but I'm nosey, and I like to see how the soap is doing. (Do you see the select shades color chart in the background?) So after the second 15 minutes of cooking (30 minutes total so far), take your soap out again. It should be much looser, with some or all of it gelling. The gelled parts will look like applesauce.

Here you can see the partial applesauce gel I’m talking about. The ungelled parts of the soap are dense and hard to incorporate, like cookie dough. Stir it up as much as possible. If you don’t have sodium lactate in your batch, the gel will be more of a Vaseline consistency. If all of the soap isn't gelling, I put it back in for another 10 minutes. If it is all gelled, I do the tongue test. If I get zapped, in she goes for another 10 minutes.

In this and the next couple of pictures, you can see what complete (applesauce) gel looks like. Very different from Vaseline. It’s very, very fluid & smooth…I hope you can tell from the pictures.

So liquid it leaks through my slotted spoon.

Yep, it’s fluid. Do you get the picture? LOL. Once it's loose & gelling, and there is no zap, I take out the portion I'm going to color (or leave uncolored, depending on whatever I added at the beginning) and add it to a Pyrex glass bowl I can keep warm in the oven. I didn’t get any pictures of this, because I had to work fast. Once that portion of the soap is away from the main batch, it cools quickly.

I add whatever (additional) color I need to the small portion I’ve removed and I stir it in (and sometimes stickblend if I can't get it incorporated). I return the small portion I reserved in the pyrex bowl back into the oven, covered, to help it stay fluid. This takes about 3-5 minutes. It won't be fluid, like the main batch, it will have lost too much heat, but it will be the consistency of mashed potatoes. Doesn't matter anyway, since when you add it to the main portion, the heat of the main portion will remelt it.

Once the main portion has cooled enough, but is still hot and fluid, I add a little fragrance. If it steams back in my face, I wait another 3 minutes or so, while stirring (to expose all parts of the soap to air to help it cool). I would say you can add your goodies and fragrance no sooner than 3-5 minutes after removal from the oven. It might take as much as 10 minutes before the soap is cool enough to add goodies to, but I wouldn't wait any longer than that if you want to be able to pour your soap. If you wait too long it's like trying to stir candle wax (and it has that appearance).

Here I am, adding Ocean Mist to the main portion. After adding the fragrance, and stirring it in really well, I take the small bowl out of the oven and add it in glops to my main pot. I then stir and mash up any large lumps of the reserved portion, and make "trails" with my spoon out of the colored portion--kind of a modified CP "in the pot" swirl.

Here I have added the chunks from the Pyrex bowl. They are still soft, but not fluid. It’s hard to tell from this photo, but if you look beyond the chunks, you can see how weird the main portion of the soap looks. Hot process can be finicky about fragrance just like cold process, too. When I added the fragrance, it stiffened up almost immediately.

Then, I pour into my molds, and depending on how fluid the soap was when poured, I bang the heck out of the mold and mash the soap down with freezer paper.

***caution*** the soap is still very hot. Protect your hands with gloves when you touch the soap through the freezer paper.

There she is, snug and comfortable in my soap mold. The top looks pretty rough, but that trims off easily. I’ll have to show you a pic of the cut soap later, since I uploaded these before the batch was ready to cut. I’m warning you now, though, it’s unimpressive. I didn’t alter the color of the reserved portion enough to make the swirl contrast with the base color. Instead, I’ll show you another batch I ‘swirled.’ I use those annoying quotation marks because a swirl in hot process is different from a swirl in cold process. HP looks marbled—at least at my level of skill.

Not the greatest picture, but the soap is really pretty, trust me. Very smooth, slightly waxy, but no pumps and bumps. Smells heavenly, too. Scented with the Scent-Works lilac & colored with select shades. Well, there ya go. I hope you were at least entertained.

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