yesterday's question about why some of my lotion recipes are so thick - I used to agree that your recipes came out awfully thick, but then I learned to account for evaporated water. I now make sure my vessels that contain my ingredients for heating weigh the same before AND after heating. I make up the difference with distilled water that has been heated and held.
If you're not compensating for water amount, you will get a thicker lotion than you expected! Let's say you need a grand total of 70% water in your lotion. If you heat and hold for 20 minutes, you might end up with a total of 60% water in your your lotion and that's going to make for a much thicker lotion! So make sure you measure your water phase with container at the start of the heating and holding process and the end, and add enough heated water to get back to the number you need in the recipe.
And this relates to this question from Always Looking 4 1 More (from this post): I love formulating but I've been trying to keep my formulating (and my life) as healthy as possible. So I'm wondering how much of the "good stuff" that we use many natural oils, aloes, etc. for is retained in it after we heat & hold for 20 mins. or so? It seems the "good stuff" will all be destroyed and all we have left is a product that just "feels good and smells delightful". Are we inadvertently sending nutrients out into the air while trying to kill different kinds of germs and germ-causing elements in the oils and waters (eg, aloe)?
in this post, but let's summarize that before moving on to the water soluble ingredients Most oils have a smoke point well over 100˚C (for instance, grapeseed oil is around 216˚C and camellia seed oil is around 485˚F!), and we're heating our products up to 70˚C/158˚F and holding them, so the oils will be just fine. Yes, we might speed up rancidity slightly, though not by much. We aren't ruining any polyphenols or phytosterols or lovely fatty acids or hurting the oil in any way. On the other hand, not heating and holding our oils can have a huge impact on the emulsification of the product, and a failed lotion is definitely something that can ruin our oils and waste our money!
As for the water phase, the only things we add to the heated phases are things that can stand the heat! Anything that can't stand the heat goes into the cool down phase, which is at 45˚C or 113˚F. We aren't boiling our ingredients, and any evaporation we experience will be from the water portion of the lovely ingredient (every liquid ingredient has some water in it!). We are ending up with a more concentrated of the ingredient (for instance, aloe or a hydrosol), which isn't a bad thing. (Although we should add the water back to the product, so it'll all even out in the end.)
If you're really worried about things going out into the air - although I can't think of anything other than water and some smells - you can put a lid on your container, but just watch it to ensure that your ingredients stay around 70˚C or 158˚F. (Don't put the lid or plastic wrap on tightly!) This will also reduce the amount of evaporation in the product.
The good stuff we want from our ingredients include vitamins, minerals, fatty acids, phytosterols, polyphenols, polysaccharides, and more, and those things are either heat tolerable or not. Something like panthenol wants to be added at the cool down phase because it can't tolerate heat, whereas aloe vera can.
If you're in doubt as to whether your ingredient can stand the heat, click here for some ideas on when to add our products to the various phases! And here are two posts on evaporation - surface area and evaporation and compensation for evaporation when making products!
And keep the questions and comments coming by commenting on a post or writing to me, Swift, at firstname.lastname@example.org! I'll do my best to get to your question in the coming days!