Future cleanup

That's odd. I flush my AB with 91% IPA after shooting Future and never had an issue.

Roger

This is just a wild guess; You may have missed a bit of Future in you original flushings or there was a small bit of a prior paint still in the brush and the Windex-Alcohol caused the resultant "sludge". But your clean out method should have been OK.

Maybe a another flush through or two, next time, before shutting down. 

Steve,

You are probably right. The last couple of times I painted I didn't disassemble the AB, I just flushed it out. There was probably some residual paint left. My own fault for tying to take a short cut. I will do a thorough cleaning before and after the next time is shoot some future.

Roger

I typically clean up my brush with Windex and alcohol as well.  I will also, at times, place my finger over the end of the brush and "back-flow" air into the cup and then continue flushing.  Doing this has never caused any problems for me.

Some acrylics such as Testor's Acryls actually do not thin with alcohol. They use a proprietary thinner and alcohol will just make it a hard and impossible mess.

I have and old air brush I don't use. Dedicating it to future is an excellent idea. Thanks for all the feedback everyone!

Roger