Making a water-in-silicone serum, Nanette asks: How do you determine the correct percentages of powdered ingredients? 2% of powder A could weigh significantly more than 2% of Powder B.
These kind of conundrums are the reason we weigh all our ingredients intead of using teaspoons or tablespoons. How much allantoin are we adding if we use 1 teaspoon or 5 ml? How much if we use 10 ml? And so on. It's so much easier to use 0.5 grams in 100 grams of product and know that we are using 0.5% allantoin in that product.
How to convert any recipe from percentages to grams? Convert the % sign to the word "grams" and you will have a 100 gram batch. If you want 500 grams, convert the % sign to the word "grams" and multiply by 5. And so on.
Always always always weigh your ingredients. Don't do the "5 grams of this, 1 ml of that" recipes as they are hard to scale up when you want to make bigger batches. As well, how do you know how much of something you've used in percentages if you've added 5 ml of something to a 100 gram batch?
Oils have a specific density of 0.90 grams per ml. So adding 5 ml to a 100 gram batch of product means you've added 4.5%. Glycerin has a specific density of 1.263 grams per ml, so added 5 ml to a batch, means you've actually added 6.315% to your product.
So the short answer to your question, Nanette, is that 2% of powder A and 2% of powder B will always be the same if you are using weighted measurements! (You'll have 2 grams of A and 2 grams of B!)
Why we weigh ingredients!
How to convert recipes from percentages to weights!
How do I figure out the volume of a recipe? Specific gravity