On my Patreon feed, Sally asked: Under what circumstances can you tinker with a "finished" product" For example, a batch of shampoo isn't as foamy as I like. Can I melt some SCI and add it after the fact" Or can I make a large batch of lotion and then divide it and add separate fragrances afterwards" Are there categories of fixes than can be tried, or categories where just cut your losses and start over again"

This is a big and fantastic question, so I'll do my best to answer it in as much detail as I can. I will definitely be updating this post regularly as I think of more things!

Why wouldn't we want to add things after the fact"

1. It might mess up the emulsion. A lotion can only take x% oils before it falls apart. For instance, if you have a lotion that has a 24% oil phase and you've used 6% Polawax, adding even 1% more could make it fall apart.
Related post: Polawax and the 25% of the oil phase rule

2. It might mess up the emulsion if you have to heat it as a lot of emulsions can't take being heated again.

One of the things that comes up a lot is wanting to make the lotion thicker after it's done. One trick is to make a second batch of the lotion with more thickener, so when you combine the two lotions, you'll have the amount of thickener you want. So let's say you made a 100 gram batch of lotion with 3 grams of cetyl alcohol in it, and you wish to have it thicker, you could make a second 100 gram batch with more cetyl alco...