I recently used a Minwax Oil-based Polyurethane to seal my exposed brick. The problem I encountered is that on some of the bricks they turned an opaque color. I'm trying to figure out why! It's only happening to certain bricks. I started trying to problem solve and I've eliminated the following possibilities: 1. I removed all dust evenly. 2. I acid washed the wall with a mild acid, and rinsed thoroughly, and where the acid was most concentrated, the polyurethane didn't discolor.

Here's my hunch: 1. Some of the brick absorbed more moisture and weren't completely dry (I did let it dry for 48hrs.) so the polyurethane reacted with the moisture? 2. The bricks that turned opaque didn't have enough polyurethane on them...(the following morning I applied a second coat to a small area of the opaque brick, and it turned it clear again...but I haven't seen it dry yet (went to work)....
IF ANYONE CAN GIVE ME SOME GUIDANCE, I WOULD REALLY APPRECIATE IT!

Help - Brick Sealing

bricks