CPHP is a rewarding way to make a quick batch of handmade soap. Unlike the Cold Process soap method, which can take up to 6 weeks to fully cure, you can use properly made CPHP the same day you make it. We're talking instant gratification! This method also allows you to make smaller batches more reliably. There are other ways to achieve Hot Process soap...in the mold, in the oven, in a double boiler. This method is my current favorite.
Both types of soap making are enjoyable, for different reasons. Cold Process soap is a virtual Artisan palette for swirling and layering techniques. But, it is much less forgiving of creative additives than Hot Process. Hot Process soap requires less essential or fragrance oil by measure than the same amount of Cold Process soap, so it is more cost effective. Colorants can be added as soon as the soap traces, so there is time to adjust or deepen the color if necessary as it cooks. Bars of Hot Process soap offer a bigger initial burst of bubbly lather. The trade off? A bar of Hot Process soap doesn't last as long as a bar of cold process.
I use a couple of different crock pots, depending on the amount of soap I want to make. The Turkey roasting oven will accommodate a 6-8 lb. batch nicely. But for the most part I use a 4 quart Crock Pot, for a batch that makes about 12 bars of soap. It is helpful if your crock pot has a "keep warm" setting. It gives you a little more time to get the soap into the molds or split the batter into two different kinds of soaps.
I made this batch of Peach scented soap for my daughter. I strongly recommend you have prior knowledge of Cold Process soap making methods, and experience with basic safety procedures required when working with Lye, before jumping in to make your first batch of CPHP.
Any Cold Process soap recipe will "work" with CPHP soap. A higher ratio of oil to solid fats makes for a smoother CPHP soap, i.e., Castile recipes work particularly well in the crock pot. You can dissolve sugar in the water BEFORE you add the sodium hydroxide to boost the lather. Make sure the sugar is completely dissolved in the water before adding the lye. A higher proportion of solid fats is recommended if you wish to use the fancy little plastic molds. Don't discount the water in CPHP! You may even want to add a little more water (when dissolving the lye) or end of the cook, to smooth out the gelled soap. Sodium Lactate is another optional additive that helps smooth the texture of CPHP.
The fats and oils have been weighed and placed in the crock pot.
You now have two choices. If using room temperature lye solution, heat the oils and fats till the fats are at least partially melted, then stir in the lye solution.
If the lye solution is newly mixed and still very hot, it can be stirred in to the lumpy fat & oil mixture, and the heat of the solution will melt them as it is added. Use a stick blender as a wand to hand stir the fats as you add the lye solution in a steady stream. Once all the solution has been added, hold the stick blender vertically and turn on, using the low speed setting.
Once squiggly lines can be traced across the surface of the liquid soap with your spatula, the stage of the soap is called "Trace". This is the time to stir any colorant into the soap. Next, put the lid on the crock pot and cook on HIGH for approximately 30-40 minutes. (If you are busy doing other things, you can use the Low heat setting, and plan on the process taking a lot longer.) You can lift the lid halfway through and stir briefly, moving soap that has gelled on the edges towards the center to mix it in.
It cooked on HIGH for 35 minutes, and the soap has changed to a clear gel consistency. It has completely gelled. Using a teaspoon, remove a tiny bit of the soap. Let it cool a minutes, then rub it between your fingertips. It should feel somewhat "waxy". Now is the time to thin it out with one or two tablespoons of water or milk, if the gel seems dry or stiff at the edges. It will definitely require a bit of stirring to incorporate the liquid into the gel thoroughly. If you are adding herbs or clays to the soap, stir about 2-3 Tbs. Jojoba or other super fatting oil INTO the herbs in a small container. Then add them to the finished soap. Allow the mixture to cool about 5 minutes. Ideally, add the Essential or Fragrance oils when the mixture is 140 degrees or below, and stir them in as quickly as possible.
Have a mold ready. A plastic storage box is fine. A silicone mold is ideal, for single bars. There are so many to choose from at soap making supply stores! Some come in special, decorative shapes or designs, and the silicone works for cold process soap as well. This batch of soap will completely fill this mold, yielding 12 bars.
The gelled soap will need to be glopped into the mold cups quickly, as it gets thicker with every degree it cools. Pack it into the mold with your spatula, pressing and compacting it firmly.
This large, curved heavy duty spatula is my favorite tool to use for packing hot process soap.
If your gelled soap is thinned properly, it will be easier to fill the molds. If you add too much liquid the soap will take longer to firm up. I didn't thin this batch, as I wanted to show you how the surface looks if you don't thin it. It doesn't hurt the finished soap, but the appearance of it may be a little shaggy, with a few air holes. This was great soap, nonetheless!