Formulating facial moisturizers for wrinkled skin, Tina asks: I have recently found your blog and instantl fell in love :) Thank you for al the effort you are putting in it, there are soooo many interesting and useful information for a hobby cosmetic maker. I do have one question though - I read a couple of your facial moisturizer recipes and the percentages (water phase, oil phase and cool down phase) don't add up to 100%. Did I just added thing up wrong or is there a mistake?
Thanks for the kind words, Tina. I'm glad you like the blog!
Recipes should add up to 100%. Mine may not for a few reasons. I might have indicated you can use 0.5% to 1% preservative, so the recipe might add up to 100.5% with the 1%, or I might have an optional ingredient, or I might have messed up on the math. The easy thing to do is reduce the water so you get 100% total.
Most formulators get around this problem by putting "water, q.v." meaning, use as much water as you need to make up 100%. I don't use that on the blog as I think it might be a bit confusing at times.
In the grand scheme of things, being a titch over or under 100% isn't the end of the world. Being a lot away from 100% is as you aren't getting the right percentage of ingredients, which isn't a huge deal for something like an oil, but it is for an emulsifier, preservative, or ingredient that has limited solubility.
The recipe in question has 102%. This isn't right - it should be 100% to 100.5 to account for the variable preservative - so I've altered it by removing 2% water. Why did it total more than 100%? I got the math wrong.
If you see a recipe that is out of whack - meaning more than 102% and less than 98% - please comment and I'll fix it!