Mold, Mildew

Published on March 4th, 2013 | by Henri


Finishing a window frame that is discolored by mold

Q.  I am trying to apply finish to new windows in a home that I’m building myself.  The windows were put in a year and a half ago and I am just now getting around to finishing the wood. The windows are Andersen, vinyl-clad on the outside, wood inside.  The problem is this, in the course of the year and a half since putting the windows in, we’ve had a moisture problem (timber-frame home, no air exchange). Most of the upper sashes and some lower ones have had mold/mildew grow on them and they’ve now discolored.

I’ve done some reading and had calcium hypochlorite recommended, but wanted to check in with you. I want the stains completely gone before I apply an oil-based stain and polyurethane. Is that possible? Will sanding the affected areas and then hitting them with a dose of the hypochlorite get rid of that stain? Is there anything that I can do to get rid of them? At what point is it safe to apply the stain and polyurethane? If sanding and chloride is the answer, what grit should I use and how long should I leave the chloride on for? I’m a little afraid to sand too much as I don’t want to go down too far and affect the integrity of window itself. Any help would be greatly appreciated.

A.    Apply full-strength fresh Clorox bleach (sodium hypochlorite) or calcium hypochlorite (swimming pool chlorination compound) to the stained areas with a small brush until the mold is removed. Let dry and follow up with your finish of choice.

If the mold is so deeply ingrained that these chemicals do not completely remove it, try oxalic acid crystals, which you can buy in paint stores. Be very careful with all these chemicals; get full instructions in handling them and wear eye and skin protection.

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