Have you ever noticed small, gummy bumps along the edges of your floor boards during the warm summer months? Chances are you are a victim of polybeads. Polybeads are soft, gummy bumps that are tracked across the floor. If left untreated, these bumps will solidify along the edges of your floor finish.
As the VOC regulations tightened up in many parts of the country, oil modified urethane solids (OMU’s) have been raised in order to comply with regulations. All OMU’s dry from the top down. Since higher solids with low VOC OMU’s are thicker, they do not flow through the cracks as well. This causes the drying process to slow down significantly. The surface will dry, but the liquid underneath dries so slowly that liquid may remain in the cracks of the floor boards for six to nine months.
If the humidity is high, the moisture content in wood will rise. This will cause your wood to expand and the cracks to tighten up, closing up any remaining cracks and squeezing the semi set liquid. As the liquid is squeezed, some goes down the cracks and some rises to the surface. The portion that squeezes up will form a bump in the dried surface film with a liquid core from underneath. Polybeads usually result from jobs done in the spring about three to four weeks on either side of Easter. That is the time of the year when the floor will have cracks open due to floor boards shrinking from the winter months. If the finish is not completely dry between the boards by the time spring arrives, the seasonal rains will raise the ambient humidity and cause the wood to swell and squeeze out polybeads. You are more likely to encounter this problem if you cross mop with lambs’ wool. If you start across the grain, make sure the lambs’ wool can push enough finish down the cracks. Start in line with the grain to minimize this problem.
This is a problem that is difficult to prevent. Our best advice is to coat wood with a heavy applicator that leaves thin films for the best drying conditions. For optimal results, make sure you have plenty of air circulation to help with the drying process. We also recommend that you leave each coat to dry before applying the next coat.
To fix polybeads, scrape the finish with a putty knife and wipe the liquid residue with mineral spirits on a rag. This “squeezing up” will stop when one of three things happen. 1.) All the liquid has squeezed out and has been wiped up. 2.) The finish reaches a cure point hard enough that it can’t be squeezed out. 3.) The floor will start to drop some of its moisture and the wood will shrink back, relax the pressure and the bumps will stop forming.
Note: Some contractors have added oil drying agents, such as Japan Dryer, to their finish thinking they are speeding the drytime and acting to prevent the problem. In most cases the problem will be worse as the surface film dries faster. The OMU needs oxygen to cure with or without Japan drier.
Micah Petersen, Senior Product Manager for Basic Coatings, spent the first 15 years of his career as a Research and Development Chemist before becoming Product Manager. In his free time he enjoys spending time with his family and a multitude of outdoor activities. For further questions regarding hardwood floor care and Basic Coatings, please email Micah at Micahblog@basiccoatings.com