Or here is a quick refresher:
Water at 100% of shred weight
Glycerin at 75% of shred weight
Stearic acid at 20% of total batch weight
Your favorite liquid oil of choice at 10% of batch weight
Your colorant of choice (or none if you like the color).
Melt everything together. It will be soupy.
Cool completely. It will be like Play-Do, maybe a little more or less firm than that depending on your shreds.
Start whipping. Add FO and preservative.
After it has fluffed up, add your desired amount of scrubby ingredients. Mix just enough to incorporate well.
Be careful not to overmix, or it will get runny again from heat (easy to do with small batches).
That's not a big deal really, unless you are really keen on a specific fluffiness quotient.
I’m sorry that I never saw this until today. You can read about salting out soap at the Soapy Stuff website, here.Mobjack Bay, what do you mean by "salted out the soap"? Do you mean that by adding the salt, the soap became less soapy, i.e. less suds?
Now that I’m back from my trip, I was really anxious to get a rough idea of where I ended up, but I’m definitely going to need to check the calculations before I share them. If only the aliquot I adjusted had been 100 g instead of 75 g. What was I thinking…
Preservatives are always based on the total. Remember we cannot see bacteria until it’s overwhelming the product.My best estimate of the final percentages I used in the foot scrub are in the table below along with the percentages for the initial batch and adjusted percentages I want to try for a small next batch. As a reminder, the initial percentages resulted in a scrub that was still a bit waxy after 24 hrs. I used the modified scrub in the shower this morning and like it, but I think it can handle a wee bit more oil and exfoliants. The current version rinsed clean with no oily feeling left on the skin and my skin also didn't feel tight or dry. That was okay, but I want to see if more liquid oil, like MCT, will loosen the scrub a little. For the next attempt, I dropped the sugar a bit to compensate for increasing the pumice and ground apricot seeds and also rounded the recipe percentages a bit to make them easier to remember in use.
With so much sugar in the mix, the preservative level in the current batch is only 0.15%. Should the amount of preservative be calculated based on the weight before adding the sugar, or the final batch weight after the sugar is added?
As a reminder, I used relatively fresh tallow & lard-based soap (palmitic & stearic = 30%, approx 5% SF; 20% CO) that was made using 40% lye concentration. I don't know how much difference the initial fatty acid composition of the soap makes when this much sugar is involved, but prior to adding the sugar my initial batch had a bit of a Silly Putty/waxy texture and a hint of that texture at the 24 hr mark (see my previous posts).
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By itself, yes, and so is honey. But adding sugar to a product is a completely different story, it’s adding bug food.My understanding is that since sugar is self-preserving, that for products with a high percentage of sugar (like these scrubs), that you base the preservative on batch weight minus sugar weight.
I have several of Susan’s ebooks as we as being a patreon. I still believe the amount of preservative is based on the total amount of product. I also have a masters degree in chemistry.My understanding is based on the recommendation of at least one professional formulator (Susan Barclay of SwiftcraftyMonkey) who calculates the preservative on the pre-sugar weight if sugar is at least 50% or more of the total product weight. She has some interesting reading on the subject to explain the science behind this, i.e., the “water activity” of sugar. She also cautions that she is only confident that this works if one isn’t adding other strong bug food like ground botanicals, etc.
Another professional formulator, Sandra LaBossiere of DIY Bath & Body, also bases her preservative on the pre-sugar amount, but doesn’t explain why. I assume she is relying on the same science shared by Susan.