White Line Syndrome

White Line Syndrome

Board /Crack Beading or Poly Bubbles:

The Problem:

Beads of finish forming in the joints.

The Cause:

Most finishes and stains dry from the top down. When the first coat is applied, ( and especially when a very heavy coat is applied) whether it is a stain or finish, it seeps down into the cracks between the boards. The material therefore stays comparatively wet because there is no air movement. Usually, at this point three things happen:

Additional coats of finish are applied
The floor is covered
As additional coats are applied, the problem is compounded. Then covering the floor may affect the dry time by locking the solvents down in the cracks. In time the floor expands and contracts. Expansion pushes the boards together and the still wet material down in the gaps is squeezed up, forming the beads.

How to fix the problem:

It has to be understood that this is NOT a finish problem. How to know? The finish looks great on the face of the boards for all coats; the only issue is the cracks.

The only real solution to the problem is time. Allow the floor to expand and contract and just keep removing the beads that have cured or hardened with a putty knife or scraper. DO NOT attempt to screen the beads off, this will cause circular scratches in the surface of the finish. If there are bubbles that are still soft, remove them with a scraper then wipe the area with a rag dampened with mineral spirits.

How to avoid in the future:

Apply the sealer, stain and or finish as per manufacturer's recommended instructions using the correct coverage rate. Remember more material is not better as the general rule of applying any finish is that 2 thin coats are better than 1 heavy coat. Watch for excessive space in the boards. These can be trowel-filled (as per manufacturer's instructions) Also pay attention to the factors that affect dry time. Floors should be installed at normal living conditions. That means, for new wood floor installations, all windows and doors should be in place, all wet trades done and the HVAC system running. It is important to control the job site environment. Avoid high relative humidity, above 90% R.H. and lower temperatures below 50 degrees F (10 C) that can seriously slow the drying time of sealers, stains and finishes.

Once the floor is finished, allow it to cure appropriately before covering. Check the manufacturers technical sheets for correct dry times.