Dear Don,
 Despite living in a humid climate here in FL as you do there, it has been a surpise to me when some acrylic paintings I had laying on top of each other stuck with some of the paint coming off!  It seems that the acrylic medium wasn't dry even when I thought it was.  How long should I expect it to take for drying do you think?  Would using a hair dryer after a few days help assure that stickiness won't happen?  Setting them out in the sun?  One also stuck to a frame where it touched!  These had been in the a/c studio area for at least 10+ days.  I had no idea from feeling the surface that it wasn't completely dry.  
 I do admit that I tend to use gel or medium in most of the work.  I like the texture, but I was sure they were dry.
 Very annoying.  Suggestions?  Thanks, Brownie
 

Gel medium as a final finish stays tacky and will stick paintings togather. I use a polyurathaine water based final over the acrylic. It's hard and stays hard. They use it on bowling ally floors. Get it at any good paint store, buy the best brand they have. I delute it 1:1.

Thanks for the idea, Don.  I had assumed all acrylic artists' products dried fairly fast, certainly with a week or two!  When using gel medium in my actual painting, does it need longer to  set before putting a polyurethane coating (water based is OK, right?) over it?    
Brownie

When its dry to the touch it's dry. Give it the final water based layer. It will keep it from being sticky.