I was wondering if there was a way to make bubble bath fairly cheaply, and in fairly large amounts.
A few things, though: no retail products (in the sense that it should be from fairly raw materials - soap, salt, oils, etc. No shampoos or anything). And as little heating as possible.
Thanks 
Seriously, though, yes, just use your choice of dish soap (which actually means dish “detergent”). We found that the clear kinds worked nicely for the kids when they were little and wanted bubble bath. It’s a lot cheaper than the cartoon merchandising tie-in bubble baths, and being clear, didn’t look quite so much like “Mommy, that’s just dish soap…” to little eyes.
Just a big squirt in the bathtub, lots of bubbles, very cheap.
Oh, just realized, you’re asking about manufacturing bubble bath? Well, just find out whatever’s the active ingredient in dish soap, and use that. Diluted.
Here’s a link for you:
http://www.recipesource.com/misc/non-food/beauty/00/rec0009.html
If you don’t like that one, you can search on Google: http://www.google.com/search?sourceid=navclient&q=how+to+make+bubble+bath
In a nutshell, to make soap you need a fat/oil and an alkali (lye solution.) For bar soap you use Sodium Hydroxide and for liquid soaps you use Potassium Hydroxide, which is harder to find.
There are several sources for learning to make soap, but the only specific liquid soap book I know of is by Catherine Failor.