Blowing Agents/Do they work?

Nowadays I have alot of customers wanting thick walled parts molded. I've read about and talked to some vendors about blowing agents. Supposably this additive is suppose to create a reaction inside the plastic that forms gas pockets in result push the plastic out against the cavity walls reducing sink marks. Has anyone ever tried this before? If so whats the thickest section you've succesfully molded.

I've used them several times in both nylon and PE. Parts with high gloss or surfaces would not be good. Looks like splay. Poor man's blowing agent is to try a little baking soda. Make sure you get compatible agent for your material.
I've made some 1/2' thick walled parts, Shrink is alittle of trial and error, if the parts aren't high tolerance like pallets and dunage works OK.