Hi John, the problem with a "basic" formula is there are a lot of variables to take into account depending on which equipment you have and what type of foam you want to make. I'm not sure which "the book" you're referring to but ours, Modernist Cooking Made Easy: Getting Started
, has a good section on foams breaking it down into the different types with basic ratios you can apply to any (well, almost any) liquid to create that type of foam.
We've also excerpted some of this information in our guide to modernist foams
. Specifically, you can scroll down to the "Stabilizing Foams" section and the last three sections which are on light, heavy, and whipped foams. Those sections will give you basic ratios you can use to turn anything into that type of foam.
I hope that helps some.
Thanks and happy cooking!
Modernist Cooking Made Easy