hard layer on top, soft on bottom

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Jun 10, 2024
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Mississippi, USA
Greetings Soapers. I'm looking for some help. I have been using the same recipe for a while but my latest batch behaved oddly so I was wondering if anyone could offer some insight.

Basic recipe: 5% castor, 12% coconut (76), 10% Olive Oil (usually some infusion that varies by color), 10% Beef tallow, 53% Lard, 10% Palm oil; 0.5 fragrance ratio; 2:1 water:lye ratio. Other additives: 0.29 oz goat milk powder ppo, 0.57 tsp clay pop (type varies by color), 0.3 tsp sodium lactate ppo, 0.43 tsp sorbitol ppo, 0.5 oz fragrance ppo.

The goat milk is reconstituted from powder in dH2O and frozen. The sorbitol and NaLactate are added to the goat milk/lye solution. The goat milk/lye is kept below 75degrees to prevent scorching of the sugars. Room temp lye/goat milk is added to 92 degree oils. The temp of batter after combining lye and oil is around 86d F. The batter is poured into a silicone mold at light trace and placed in the freezer. After ~15 minutes, the loaf is sprayed with IPA and covered with plastic wrap. The soap is left in the freezer for about 4 hours, transferred to the fridge for an additional 4 hours and then removed from fridge and left at room temp until 24 hours after pour. The soap normally is hard enough at this point to cleanly remove from the mold and to cut. I usually wait another 24 hours to trim and stamp the bars. At that time, the bars are pretty hard - hard enough that it need quite a bit of pressure get a good stamp.

The current soap was made with alfalfa/parsley/spinach infused olive oil, 1/32 tsp green chrome oxide, 1 tsp French green clay and Crafter's Choice Night Blooming Jasmine fragrance (first time I've used this fragrance).

I always add the sodium lactate (60% solution) and sorbitol (70% solution) to the lye/goat milk solution. This time I added the sodium lactate and sorbitol to the goat milk before freezing to make things a little easier. Before I made this change, I did some research to see if there was any reason chemically not to add the NaLactate and sorbitol to the water before adding the NaOH but there didn't seem to be any reason not to and I thought it would simplify things on soap day.

Result: The batter took much longer than usual to reach trace and it was just the very lightest trace at pour. Then the next day, the soap was really mushy when I started to try un-molding it so I left it in the mold for an additional day and tried again. The soap was a little harder so I did get it out of the mold but it was super soft in all the corners and it came out a little messed up with some soap stuck in the corners of the mold. I left the loaf on the drying rack for yet another day before cutting. At this point there was a visibly different hard layer, kinda translucent?, on the top (see picture) but the rest was uniform and still on the soft side - harder than the day before, about as hard as my loaves usually are 24 hours after pour.

Questions: What caused the layer on top? Is the soap safe to use? Does adding the NaLactate or sorbitol before NaOH make a difference? Was there something else that I did or used that resulted in the soft soap and hard layer? Could it be the fragrance (never used it before)? Has anyone seen this before? I've been soaping for about 5 years and have never seen this...

Thank you for your help!


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I would put my money on the FO being the problem, not the way you added the SL or sorbitol. But honestly, I can’t see any separate layers in your soap. It looks great to me.
Ok, I can see it the top layer now on my laptop if I enlarge the picture; it wasn't visible at all on my phone. I'm still going to guess that the FO caused the separation, or perhaps the interaction of the FO with the alcohol that was sprayed. Whatever the cause, unless the soap remains zappy after a few days, it should be fine to use.
I was wondering about the alcohol too. Today the soap is pretty hard and a piece of trim scrap dissolved in distilled water pH'd at 9.4 with a pH meter so I think it might be OK after all. Thank you so much for your help!
You are welcome, and glad that it turned out. As an aside, pH does not tell you whether the soap is lye-heavy or not. You can read more about that here (scroll down to the section about pH and lye-heavy soaps).

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