I can't say I know any specific gels or conditioners that encourage shrinkage, but I do know a couple of techniques that cause my hair to shrink more.

First, applying products to my hair when it is not soaking wet. If I apply products to soaking hair, my curls elongate, but if I apply products to just damp hair, it shrinks up. I believe this is because the products are not sealing as much water into the hair, so the hair is lighter.

Second, plopping. The longer I plop, the more shrinkage I get. I'm assuming this is because the having the hair piled on top of the head means that its weight is not pulling the curls down.

I agree with CurlieCutie that protein can increase shrinkage for some people. This is a great idea for a thread and I hope others chime in with condish/products recs!
Originally Posted by Hootenanny
I've never plopped before but I'm gonna buy a flour sack thing and try it. Also, by coincidence I put my usual products in my hair today after drying it more than usual, and also tossing it around and scrunching the products in and letting my hair finish drying more messy than usual (hard to explain, but just played with hair a bit and separated hair so it wouldn't dry all in one piece so to speak) and I have more volume now. So u may be right about applying products in semi dried hair. I can't wait to try plopping it!
Medium texture, normal porosity, normal elasticity