Published on May 29th, 2014 | by Henri


Polyurethane caulk needs to cure for a week

Q.  I know that you are a fan of polyurethane caulk for its performance, and I have used it for some time. I had a curious experience recently, and wonder if you might have any insight.

My shower stall was in need of some caulking, both inside and out. Unfortunately, several hours after I completed the job, my son used the shower. I noticed several days later that while the caulk on the outside of the shower stall retained its white color, the inside caulking, which had been exposed to running water, developed what appear to be small rust stains.

There is not an overabundance of them, but enough to be somewhat annoying. They have not changed or grown since I first noticed them, which has been about two weeks now. I can only assume that the water had a reaction with the caulk before it had sufficient time to cure. Are you familiar with this phenomenon?

A.    Polyurethane caulking needs to be allowed to cure without getting wet for seven days. Otherwise, it turns somewhat pink. Unfortunately, you will have to remove it (which is not easy to do) and put new caulking if you cannot live with the change.

Or try to apply a thin film of the same caulking over the stained one after making sure it is thoroughly dry, and be sure not to let it get wet for a week, if that is possible. Otherwise, choose a different brand such as DAP Kwik Seal Plus Premium Kitchen & Bath Adhesive Caulk w/MICROBAN, a mildew retarder.

I have used it as well to see how it would hold up, but was disappointed over time as it separated from the tiles. But it did remain sparkling white. It has some silicone in it, and my experiences with silicone products have not been too successful, which is why I prefer polyurethane caulking compounds.

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