I recently had a past student ask for help in figuring out some issues they were having with their CP soap. The last couple of batches had come out more greasy and oily than usual and seemd to be overly superfated. She made sure her measurements were correct (using two scales). She hadn’t started using any new ingredients or batches of oil. I drilled her about this and that and finally asked how she stored her lye. She kept her lye in a bucket from the supplier. She was now down to the bottom of the bucket. I told her to soap using a fresh bucket of lye and her soap came out perfect!
What I suspect is since her lye was stored in a bucket (not in a plastic bag) each time she opened the container and put the lid back on she was letting in fresh air with moisture that the lye was absorbing. She did have a bit of clumping which was a big clue. So she was soaping with lye that had absorbed moisture therefore greatly increasing her superfat. The solution? Keep your lye stored in plastic bags with the air squeezed out. Here’s what I do.
I get the lye from a supplier and make a batch or two of soap.
Pour the lye into a baggy and roll up nice and tight squeezing the air out.
Rinse out the container and store the bagged lye in it.
If you’re a big time soapmaker…going through several containers of lye a week then you probably don’t have to worry about this. But if your lye sits around for a bit between use…make sure you aren’t storing away air when you store your lye.