Real estate

ASK THE CARPENTER

Repairing wood beset by blotchy ‘blooms’

Q. I’ve sanded and restained all of the woodwork in a three-season sunroom. The section that I did first has one coat of Minwax stain and a layer applied about a week or more later of polyurethane (matte), as there is often condensation on the windows that was creating stains on the wood trim. We also had some leaky skylights and ice dams, so the project couldn’t be avoided. There is now some whitish “bloom” on several areas of the first phase of the project. I don’t know why and need to sort out how to clean it up. Should I apply the polyurethane on the newly stained sections? A damp paper towel works on some of the smaller spots. The room is basically the same temperature as the outside. What do you recommend?

ML

A. When you apply lacquer, shellac, or another quick-drying finish in humid or damp conditions, it can turn milky because the moisture trapped in the finish didn’t have a chance to evaporate before the finish hardened. A white or hazy finish can also result from:

Advertisement

 Too many coats of finish;

Get The Weekender in your inbox:
The Globe's top picks for what to see and do each weekend, in Boston and beyond.
Thank you for signing up! Sign up for more newsletters here

 Improperly stirred solution;

 Application to wood with a high moisture content.

It’s important to stir the polyurethane well; manufacturers add a flattening agent, usually zinc oxide, which disperses reflected light and cuts the gloss. This material collects at the bottom of the can.

You’ll need to identify the problem and will probably have to start over. Strip, scrape, or sand the polyurethane and redo.

Advertisement

If the hazy look is a small area, you may be able to try this trick. I learned it from my mother-in-law after I left a glass of ice water on a wood table without a coaster (ugh!):

 Cover the affected area with mayonnaise;

 Leave on overnight, then wash the wood clean. You may notice an improvement because the oil in the mayonnaise leaches moisture out of the finish.

 Repeat if you noticed a difference but the cloudiness isn’t completely gone.

Q. The entire attic (minus the floor) in our two-story home is insulated with soy foam. Other than the pull-down stairs, there is no way to ventilate. Mold is growing on belongings, and the air smells foul. We are not allowed to have windows in the space. Any ideas for how to ventilate? We have a similar problem in our concrete crawl space as well.

Advertisement

SUSAN, Provincetown

A. If there is visible mold, you should call your insurance agency and get a remediation company up there. Depending on your roof design, you may be able to add a ridge vent and lower soffit vents. Ask a contractor or roofer to evaluate your roof for venting options.

The Environmental Protection Agency has a useful publication called “A Brief Guide to Mold, Moisture, and Your Home.” (It can be found at www.epa.gov/mold. Be sure to click on the “Mold and Your Home” link.) In the guide, the EPA warns of the dangers of mold that grows indoors: “Molds produce allergens (substances that can cause allergic reactions), irritants, and in some cases, potentially toxic substances (mycotoxins). Inhaling or touching mold or mold spores may cause allergic reactions in sensitive individuals.”

Note: If you clean up the mold, but don’t fix what’s causing it like you are trying to do, it will grow back.

Rob Robillard is a general contractor, carpenter, editor of AConcordCarpenter.com, and principal of a carpentry and renovation business. Send your questions to homerepair@globe.com or tweet them to @robertrobillard.