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Get a Bead on Poly Beads

Aug 01, 2019

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Have you ever noticed small, gummy bumps along the edges of your floor boards during the warm summer months? Chances are that you’re a victim of poly beads. Poly beads are soft, gummy bumps that are tracked across the floor between individual boards. If left untreated, these bumps will solidify along the edges of your floor finish, or they can cause smears.

As the VOC regulations tightened up in many parts of the country, oil-modified urethane solids (OMUs) have been raised in order to comply with regulations. All OMUs dry from the top down. Since higher solids with low VOC OMUs 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. Poly beads 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 shrinkage 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 poly beads. You are more likely to encounter this problem if you cross mop with lambswool. If you start across the grain, make sure the lambswool 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 convert to waterbased sealers/finishes to prevent the issue. However, if you need to stick with OMU, try 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 poly beads, 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 to their finish thinking they are speeding the dry time 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 drying agents.

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