Fixing gas bubbles in epoxy and urethane coatings

Fixing gas bubbles in epoxy and urethane coatings

All too often during the first coat of an epoxy seal, bubbles and craters appear as the floor hardens. Gases like argon and methane can pass though the floor, causing bubbles to appear in the paint. Often, gases come from chemical reactions still being produced by the preparatory floor cleaning process. Many times bubbles can be avoided by doing two thorough scrub rinses. Pressure washing and other rinse techniques don’t penetrate deeply enough into the porous surface to keep reactions from happening. We’ve also seen gases being sucked into the room through the floor by the heating system or by natural airflow. We prescribe, here, a simple, effective solution for repairing these defects.
Many times just screening the floor and putting on another coat will solve the problem, but not always. That is, even after a second coat, there may be telltale signs of bubbling. Before re-coating, look closely at one of the bubbles. Remove any skin from the top of the bubble and see if there is a small hole at the bottom of the crater. This small hole is a sign that something is blowing through the hole, causing the bubble. Usually, screening off the tops of those bubbles will clog the hole at the bottom. As a result, no bubbles will form during the second coat. But for extreme cases, and for a positive cure, use glazing compound to fill each hole before doing your next coat. While this sounds like a big job, in fact you and a helper can fill a 1200 sq. ft. floor in about an hour.

Here are the steps for positive repair and concealment of your cratering problems. First, use a rotary scrubber and pad with a 60-grit screen to quickly go over the floor, shaving off any bubble tops and thereby flattening the floor. Next, sweep up the screening dust. Then put on those kneepads and, using a tooth paste-style tube of glazing compound and a putty knife, start filling. After all the problem craters are filled, screen again. A good second screening can be done as soon as you are finished filling. This screening will quickly remove excess glaze and blend each hole flat. Sweep again and then coat the floor.

With this extra hour of work you can be sure that the holes are all permanently filled and with no holes remaining in the floor, there should not be any new bubbles or craters. Make sure that when you mix your floor coating you don’t whip air into the mixture. Use a hand paddle for about 200 strokes then let the mixture sit for 20 minutes before using it, pot life permitting. If you suspect that your roller cover is pushing air into your product, use a mohair-style roller cover and pour the product on the floor; don’t dip the roller into it. Having the room temperature near 70 degrees and preventing wind and hot or cool spots is also helpful.

For a detailed quote of materials needed to apply epoxy paint to your floor, please visit our free cost analysis page at

For more information, contact Chris Biesanz at or phone 1-800-466-8910 or 952-888-1488 (24/7).

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