If you have read our books, or used our recipes and formulas, you'll have noticed that nearly all of them are measured in weight and show percentages, not volume measurements (ie cups, mls, teaspoons). Sometimes, you can use a volume, or even "eyeball" something, but for the main part cosmetic and soap formulas require accurate measuring, so this needs to be done by weight.
This also explains why some of your vials of pigments you purchase from us are full and others are half empty - because it is sold by weight!
This is a Soap Queen explanation of why this is so necessary for success! Check it out, as the graphics show clearly how important it is: