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Q.Over the past five years, I’ve built more than 30 laminate countertops, and I’ve never had any problems with them. Recently, however, one of my countertops started to bubble in a few places about five weeks after I built it. I tried taking an iron and heating the laminate, then flattening it with a J-roller until the laminate cooled. This worked, but for only about a week. What could be causing this to happen? And what can I do to fix this problem?

A.Merrill Glos, engineer at Formica Corp., responds: The most common cause of bubbling laminate is dimensional incompatibility between the laminate and the substrate. To prevent the problem, the substrate and the laminate must be compatible — they must respond to humidity changes by expanding and contracting at the same rates — and they must both be acclimated to the indoor environment before they are bonded.

If the laminate is dry and the particleboard is wet, the laminate will bubble when the laminate grows and the substrate either shrinks or stays the same size. It takes laminate about two days to acclimate, if air can get to both sides of the material. For a piece of 3/4-inch particleboard substrate, it takes about a week. The best substrate is particleboard, which has good dimensional compatibility with laminate. Plywood makes a poor substrate, because it is more dimensionally stable than laminate.

Solvent-based adhesives are preferable to water-based adhesives. When it comes to dimensional movement, wood reacts with moisture, not with solvent. Even with proper acclimation, if you use water-based contact adhesive, the water can disrupt the humidity balance by introducing water into the laminate or the substrate. Solvent-based adhesives tend to be more forgiving than water-based adhesives, and do not induce dimensional change problems.

To solve the problem, you’ll have to heat up a larger area of the laminate than just the bubbled area. Heat up the bubbled area, as well as the entire area from the bubbles to the nearest laminate edge. This will allow the laminate to slip, adjusting to the change in dimension. After heating, use a 3-inch J-roller to rebond the contact adhesive, rolling until the adhesive is cool and has regained its strength.