I don't know anything about chemistry, so I don't understand the % you put for each ingredient. I'm used to read cooking recipes, where they tell you 1 teaspoon of this, 1 cup of that, but I don't know how I would measure the % of the ingredients in your formulations. Maybe you have a blog post explaining this but I haven't found it yet, so can you enlighten me about how should I measure the ingredients for a formulation? Do I use a scale? a measuring cup? How do the % translate into miligrams, grams, ounces or whatever measurement system is the appropriate one?
All the recipes on my blog are in percentages and they should add up to 100% (although there are some differences in the amount of preservative used). The easiest way to convert the recipe is to think of the percentage sign as the word "grams". So if you see 70% water, you'd use 70 grams of water. 15% oil would become 15 grams of oil and so on. The recipe will total 100 grams of product.
But let's say you want to make a really large batch of lotion to give as Christmas presents. Substitute the percentage sign with grams, then multiply by how much you want to make. If you want 500 grams of lotion, you'd see the 70% water as 70 grams of water x 5 for 350 grams of water. 15% oil would be 15 grams x 5 for 75 grams of water. And so on. You'd have 500 grams of product.
You can do the same thing for weighed ounces, but it really is a pain in the bum. The easiest way is to convert the percentage sign to ounces, move the decimal one space to the left, and use that. So if you have 70% water, you'd convert that to 70 ounces, then move the decimal over once space to the left and call it 7 ounces. The recipe will total 10 ounces of product. (But this is a way more complicated way to do it!) You can multiply the ounces by the amount of product you want to make.
Why do we weigh all our recipes? For accuracy. Using cups and teaspoons aren't accurate, so we might end up with more or less emulsifying wax than we need, which can result in an epic lotion fail or end up with more beeswax than we want in a lotion bar, leading to drag on our skin. It makes it easier to replicate that awesome recipe you made last time, as well.
Here's an excerpt from a previous post I wrote on weight vs volume!
Pure water at 4 Celsius is our baseline for specific gravity and everything else is compared to it. Water weighs 1000 grams per litre - 1 kg per litre - or 1 gram per millilitre. If something is listed as being less than 1, it weighs less than water per gram. If something is more than 1, it weighs more than water per gram.
So if we see cetrimonium chloride listed as having a specific gravity of 0.93, we know this means it weighs 0.93 grams per 1 cc or 1 ml. Let's say we want 5% cetrimonium chloride in our conditioner. If we're making a 100 ml batch and add 5 ml, we'd only have 4.65% cetrimonium chloride. Not the biggest deal in the world. If you wanted to make 1 litre of conditioner and added 50 ml, you'd only have 46.5 grams of cetac or 4.65%.
Liquid Germall Plus has a specific gravity of 1.15 to 1.25. If you want 0.5% in a lotion and add it in volume at 0.5 ml to a 100 ml batch of lotion, you might have 0.575 to 0.625 ml preservative, which is above the 0.5% recommended!
If you are using a lot of extracts, want to make mineral make-up, or want to be really accurate, you can get digital scales that register to 0.1 grams. I use an epoxy weighing scale I bought at the hardware store because it's sealed and has a nice little cover that closes up to make it portable. (The last one I had wasn't sealed and I'm a bit of a klutz, so I ended up shorting it out because so much goo got under the weighing plate!) I find it works well for weighing my extracts, preservatives, proteins, panthenol, and anything else I'm adding at less than 3%.
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