And other days you find that you have slipped into the Ninth Circle of Soaping Hell. Having your soap seize is the quickest way to get there.
So what is seizing? Seizing is a result of trace acceleration, meaning that the soap batter rapidly thickens, moving from trace to beyond very quickly. (Trace occurs when the soap batter is fully emulsified and will not separate.) Sometimes acceleration causes the batter to get thick like pudding or mashed potatoes, making it impossible to pour. Other times trace accelerates so rapidly that the soap "seizes" in the pot and becomes a hard mass. This is also known as soap-on-a-stick.
So, what causes trace acceleration and seizing? Many factors can play a role:
Fragrance and Essential Oils
Certain fragrance oils can cause acceleration and seizing, particularly floral or spice scents. Some essential oils - spice ones like clove or cinnamon - may sometimes cause issues. I'm not a chemistry whiz, but from what I understand, the components and compounds in some fragrance oils can speed trace along. (Something about eugenol.) Sometimes it helps to add your fragrance oil to the base oils instead of adding it at trace. And if you know that the fragrance or essential oil will act up, try using a whisk instead of a stickblender. Also, fragrances containing alcohol can cause acceleration and seizing. I've never tried it myself, but I hear that using perfume or cologne to scent soap is a great way to get soap-on-a-stick due to the alcohol content.
Which leads to another factor: Alcohol. Using a scent that contains alcohol is not a good idea. Using alcoholic beverages in soap can also cause seizing. But, wait, what about beer soap, or wine soap? How do soapmakers successfully replace the water in a soap recipe with beer or wine? The trick is to boil off the alcohol. When I use beer in soap, I bring it to a boil and let it simmer for about 10 minutes. Then I pop it in the fridge overnight to let it get nice and cold. I've made several beer batches and not had any problems when I boil it first. (Some of the beer does evaporate, so I either simmer more than I need or simply use distilled water to make up the difference.) I haven't made wine soap yet, but from what I've read I would expect that it could be treated like beer.
Soaping temperatures can also play a role. The warmer your lye solution and oils are, the faster your soap batter will accelerate. Conversely, cooler temperatures can help slow trace. I usually soap at about 100-110 degrees F. But if I am using a finicky fragrance oil or certain ingredients that contain sugars that may cause the soap to overheat (like milk, beer, honey, etc.), I'll soap cooler, maybe around 80-90 degrees F.
Sometimes the recipe itself can cause acceleration. Recipes containing a high percentage of soft oils (like olive and avocado) tend to trace more slowly than recipes calling for a higher percentage of hard oils. For instance, Castile soap, which is made exclusively with olive oil, is notorious for taking a long time to trace. Using lots of hard oils - like coconut or palm, for example - may cause the soap to trace faster. I have heard that using too much of certain ingredients - like castor oil, jojoba oil, or beeswax - may contribute to seizes, but I cannot attest to this myself. I've never used jojoba oil or beeswax, but I have made two batches of shaving soap using 10%-20% castor oil without problems.
Another thing to consider when formulating your recipe is the amount of liquid used. You may hear soapmakers talk about a "water discount," which means that they use less water than the recipe calls for. If you use "full water," that means that your lye concentration is about 27% (meaning that 27% of your lye solution is sodium hydroxide and 73% of it is water), with water being 38% of the total oil weight. (I prefer to think in terms of lye concentration instead of percentage of oil weight because it's less confusing for me. Thinking in terms of water discounts is confusing for me, too. If someone says that they use a 20% water discount, I may not really know how much water that translates into if I don't know the water amount that the recipe started off with. And then there's the math. And sometimes I wonder if someone means that they used water as 20% of the oil weight instead, which confuses me even more. It's much easier for me to just think in terms of lye concentration because it seems more solid and easier for me to understand.) The less water you use, the stronger your lye solution will be. Soapmakers often use full water to minimize acceleration. Full water is a good idea if you are doing swirls or something that requires a light trace. Discounting water is a good idea if you want to speed along a slow-tracing recipe, like Castile. Recipes calling for lots of soft oils typically handle steeper water discounts better than those with lots of hard oils. And definitely use full water if you are using a problematic fragrance or essential oil.
And sometimes the soap gremlins are just bored and mischievous. Try bribing them with cookies and beer. Don't know if that works on them, but it would work on me if I were a soap gremlin. (Make it good beer, though. Something classy. Any kind of cookie is fine.)
Pretty cool (and terrifying), huh?
So now you know some of the causes of seizing, what a seize looks like, and how to avoid it. But sometimes bad things happen to good soapers. What can you do if your soap does seize?
If you are confident that your soap batter was blended well before it seized, you might be able to mash it up and glop it into your mold like I did in the video above. Or you can wait for the soap to gel in the bowl so that it is softer and more pliable. Once the soap has gelled from one side of the bowl to the other (insulate if necessary and peek at it after about 20 minutes), scoop it into your mold. Be extremely careful if you do this! The soap will be very hot and caustic. Wear your safety gear (goggles, gloves, long sleeves and pants, etc.)!
If the soap is too hard to mash up, or if you don't think you got everything mixed before it turned into cement, you still have a couple of options.
Hot Process Hero and Crock Pot Camo tutorials for more info on hot process soapmaking.
Or you can wait until the next day to rebatch the soap. Chop or grate the soap (if it's solid enough), put it into a stainless steel pot or crock pot, and add a little bit of distilled water, starting with a couple of Tablespoons and adding more as necessary to get the right consistency. Then proceed as described above.
A seized batch is definitely a bummer, but it doesn't mean that the soap has to be a total loss. Seizing risks can be minimized, and the soap can usually be saved even if those precautions fail.
Soapmakers, have you had a batch seize on you? What has been your biggest soap fail so far?
Updated to clarify info about water discounts and recipe formulations.