Tuesday, August 13, 2013

Tuesday Wonderings: Recipes that don't total to 100% and using emulsifiers

In this post, 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!


Anonymous said...

I have been reading the blog for a while, and for some reason I understood that certain ingredients were to be used ABOVE the 100%. Such as everything will add up to 100% and THEN we add the 1% (of that total) of fragrance and the 1% preservative equaling 102%.

Anyway, I wondered, if preservative's recommended usage is .5-1% how do we decide how much to use? Should we always use the maximum amount allowed?


mallong joan said...

hello again Susan I want to make enquiries on how to donate and get your PDF files you have and I Dont have a PayPal account and I can't register because its not opened to Nigerians ( and I understand perfectly well ,can't say I blame them) no harm intended in what I said (an Nigerian too) but I would really love to get them pls is there any other way of getting it thanks would be grateful and oh you are really awesome nice job .

Tina Svetek said...

Dear Susan,
Thank you so much for your answer! After I wrote that comment, I finally decided to go and make my own moisturizer. It turned out pretty good, but I did mess up few things. I didn't have cetyl alcohol so I decided to use stearic acid as thickener, which (obviously) made my cream a bit "heavy". I also have cetearyl alcohol, but I presume this too isn't the best choice for a thickener?
Since my skin isn't very dry, it's more mixed type skin, I think the Dry Skin Moiturizer recipe might be a bit too much for me. But I also think that the Oily Skin recipe might be too dry. Do you think I could just take the Dry Skin recipe and tweak it so that it has lower oil percentage (maybe 8 or 10% instead of 12%)?

Thank you again!