There’s a really scientific way of explaining this that can be googled BUT: here’s a basic breakdown.
As time progresses and you branch into stronger and more complicated flavors, you will find that you may only use 1-2 drops of flavoring for a large bottle of juice. Sometimes so large that if you were to try to make a small bottle, you couldn’t do it because you would be over-flavoring the juice.
So many times what you’ll do is dilute in a 10 percent solution of PG and Flavoring.
Wet in Wet
With liquids since it’s 10 parts liquid; you use 9 parts of pg and 1 part of flavor. You will have a total of 10 parts of liquid in the end.
Depending on the strength of the flavor, sometimes you may have to do a 20% solution and it’s once again 1 part of flavoring but now it’s 19 parts of PG.
Then you simply mix this at a low percent to equal what it would have been in the final mix.
This is easiest on the 10% solutions.
A good example is when I need to add .08% of a flavor to a mix. At 10% solution, you’d simply multiply it by 10 and add .8% of the mixed solution. This will allow you to make smaller bottles of juice without sacrificing flavoring or over-flavoring because one drop in 60 mls was too strong. This will be a saving grace and you can really use the added pg to your advantage. Also think about it like this: What’s going to disperse faster and better? .1 ml or 1 ml?
Dry in Wet
When you come across a dry ingredient that you need to mix, it’s a little different, but the concept is still the same. You are going to dilute ¼ level teaspoon in 10 mils of PG. Many times I’ll simply warm a small bowl of water and put the solution in it IN ITS BOTTLE to slightly warm and dissolve the crystals. Pull it out and shake it thoroughly and it is good to mix at the percent needed.
This is considered a 10% solution and will be used accordingly. Many people will do menthol crystals, em, citric acid etc in this way. Since you are dissolving into pg, and it’s a 10% solution, you still need 10 complete parts of liquid.