If you've ever made soap, you probably have encountered what's referred to as "seize" at one time or another. The chemical reaction (saponification) between the lye and the oils you are mixing has fast forwarded/overreacted itself into a big, thick mess. In a "light seize," the mix just gets thick quickly and you have to work fast. In a "super seize," it goes from liquid to glob in a matter of seconds.
Causes of Seize
There are a few suspected causes of seize. The most common suspects are fragrance oils. Some fragrance oils, because of one of the constituents/compounds they contain, can cause seize. Floral fragrance oils are the most commonly reported to cause seize -- fragrances like lilac or lily or gardenia. Some essential oils, especially spice-type oils like clove or cinnamon, can also cause seize.
Using alcohol as the liquid when making soap can also cause seize.
Guard Against Seize
First and foremost, try to prevent it from happening. Buy your fragrance oils from reputable vendors. Many will tell you on their websites if a fragrance is "prone to cause acceleration." That's the nice way of saying "watch out for seizing." If you have a fragrance oil that is prone to seizing, try to minimize it by doing the following:
- Keep temperatures on the low side. Keep your lye and oils in the 90 F range rather than the 100 F range. This helps slow the saponification down.
- Dilute the fragrance oil in some warmed oils. Take several ounces (about four times the amount of the fragrance oil) of warmed oils out of your soap pot before you put the lye in. Mix the fragrance oil into the warmed oils. Then, when it's time to add the fragrance at very light trace, add the oil-fragrance mixture. The warming and the diluting seems to help minimize the shock factor when the fragrance is added to the pot.
- Don't discount your water very much, if at all. Use two times the lye amount as the water amount. For example. if your recipe calls for 4 ounces of lye, use 8 ounces of water. With seize-prone fragrances, raise that to as much as three times the lye amount. The extra water helps slow things down considerably.
- Be prepared. If you know a particular recipe/fragrance is going to get to trace quickly, don't plan elaborate swirls or colors or additives. Just have everything ready to go -- and go quickly and efficiently.
If Seize Happens
If you've done everything above and your soap still turns out as a glob of dough in your pot, don't panic. There are a few things you can do to save the batch.
- Scoop it out and mash it into the mold if you're fairly sure that you've blended everything into the soap relatively well. It's not going to be smooth, pretty soap; you're not going to get details on single-cavity molds, but it will be fine otherwise.
- Wait for it to gel. Only use this technique if you're very comfortable with your understanding of the soap-making process and know exactly what "gel" stage looks like. The saponification process has started in the pot, and if it's sped up this quickly, you're likely to get a nice hot gel stage. When the soap is in gel stage, it will be much softer and more pliable, so you'll be able to scoop and mold it easier. Insulate your pot well with towels on the top and sides and wait about 20 to 30 minutes. After that, peek in on the soap. If it's in a good gel stage from side to side of the pot, open it up and scoop. But beware. While it will be much easier to scoop, the gel stage soap can be upwards of 200 F. And it's still quite caustic from the lye. Be very careful.
- Let it sit in the pot and rebatch it the next day. You might not even have to add in any extra fragrance; just chop or grate it and add a little water. This is the best choice if you haven't been able to get the fragrance mixed in well or if you have any sort of separation in the batch. Rebaching the recipe will make sure that everything is blended well and that you get even saponification throughout the batch.