For me, the hot process method is the quickest and easiest way to make soap. There is very little room for error and the soap turns out great 99% of the time. Still, there is that 1%, so I thought I'd try to shed some light on some common HP problems and how to easily solve them.
By no means is this a comprehensive list, but hopefully it will help you if you’re having trouble with your HP. Please bear in mind that my observations take into account that the recipe being used isn't flawed and that the equipment used (slow cooker, double boiler, oven, etc) is in good working order.
1. My soap is really thick and I have trouble getting it into the mold.
This is probably the most common problem with making HP soap. Fortunately, it's also the easiest to solve. Thick soap is usually caused by a lack of water, so it's important never to do a water discount with HP. In fact, it's a good idea to add an additional 5-10% to the recommended full water amount. I wouldn't suggest going over 10% as the extra evaporation while the soap cures can cause the sliced bars to warp or bend. The extra water may be added to the lye solution or even to the finished soap before it goes into the mold. I have 'thinned' out many a batch of thick soap by adding a small amount of hot water at the end of the cook, but it does require careful and lengthy stirring to fully incorporate into the soap.
In addition to extra water, there are a couple of additives that can help keep the soap more fluid. Adding 3-5% sugar to the lye solution before the lye is added can help keep the soap from getting too thick. It is imperative that all of the sugar is dissolved before the lye goes in or you'll end up with a caustic boiled sweet! Sodium lactate is another additive that can keep soap fluid, however, add no more than 5% or the soap can become brittle. Sodium lactate is a forgiving ingredient and may be added at any time during the soap making process. I prefer adding it at trace.
2. My soap has lumpy bits in it.
When I first started making HP, I had the lumpiest soap ever. Even the cured bars showed the tell-tale white spots. There are two main reasons for hard lumps in soap -- over-heating and over-cooking. In my experience, HP should never be brought to a temperature over 140F (60C). Doing so causes the indirect heat source to become more direct as the sides of the pot or slow cooker heat up enough to over-cook or burn the soap. The hot sides contact the soap, causing bits to over-heat and harden. While harmless, these hard bits will affect the look of the finished soap.
As with cooking soap at too high a temperature, cooking it too long will also cause lumps. A longer cook time means more evaporation -- and evaporation means harder, thicker soap. As the soap continues to over-cook, the soap will begin to form hard lumps. I have rarely had a batch of soap of any size which required cooking for more than 45 minutes.
3. My soap zaps!
Barring any mistakes with the recipe, zapping soap is undercooked. To avoid a heat or lye burn, soap shouldn't be zap tested (touching a small amount of cooked soap to the tongue) at all without meeting a few criteria first:
- Soap should be at the gel stage and there should be no parts of the soap that are not translucent. If the soap resembles cake batter in any way, do not touch it.
- Soap should be cooled before testing. While 140F isn't boiling, it can still burn.
- Soap should be rubbed between the fingers before testing. If the soap feels waxy and smooth, it's fairly safe to test, but if there are any rough or gritty bits, it should not be touched to the tongue.
If you’ve met the criteria and the soap zaps, simply cook it a bit longer.
These tips won’t solve every problem you might encounter with HP, but hopefully they’ll help you achieve more trouble free batches. If you have any hints you’d like to add, please leave me a comment. My hope is that by sharing, we can make HP a nearly fool-proof method!