Stripping Old Windows
How to get old paint off historic window sashes without damaging the wood. March 18, 2006
Question
I need to dip strip some tall (9ft total) double hung sashes from a church. Because of the length, I'm concerned about the stiles warping. The stripper would prefer to dip in lye because of old milk paint. (The windows will be repainted, so I'm not worried about color - just moisture content and movement/warping.) Anyone have experience with this?
Forum Responses
(Architectural Woodworking Forum)
From contributor F:
My experience with dip stripping is that the glue joints will be weakened, if not totally dissolved and falling apart. Also, the chemicals soften and damage the wood itself, along with the paint. If you don't want to totally rebuild the windows, you will get less damage with paint-on strippers. Also, if these windows are historical treasures, scraping and wire brushing, power wire brushing, sandpaper will do the least damage to the wood.
From contributor G:
As for wood movement, I have no idea what the dipping solution is comprised of, but if it has no water in it, you're okay. Water is the only thing that can make wood shrink and swell. Period. (I once grabbed some rubbing alcohol and put it on some wood's surface, not knowing that it is diluted with water.)
From contributor S:
Large dip-stripping tanks are usually filled with caustic soda and should be avoided for exterior timber, as it saturates the timber with caustic soda. This will leach out of the timber in humid conditions, stripping any paint that has been applied to the timber. Go with methylene chloride or CitriStrip and careful handwork.
From contributor M:
Lye dipping is a bad idea. We had big problems with stuff that was lye dipped with too long of a dwell time and improper neutralizing. The wood will never hold paint. There are other strippers you can use. You can even use a lye product like peel-away, but need to be careful it does not soak into the wood. You must test the ph. We usually strip windows with electric heat guns and protect the glass with heat shields. If you are salvaging old glass, it can be safely cleaned with lye after removal.
From contributor S:
Heat guns and old paint can be a problem, as any lead-based pigment can produce lead oxide fumes. Better to use liquid strippers, followed by wet sanding to minimize dust formation.
From contributor V:
We have stripped a number of windows and doors and find the Silent Paint Remover a viable alternative to heat guns and chemical strippers. The infrared technology operates at a temperature below the vaporization level of the lead. An alternative would be to find someone with a steam stripper system large enough to handle your windows.
The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).
Comment from contributor W:
I worked for a painting contractor a few years ago when we had to strip 100 years of paint off of exterior windows in our state capitol building. Because of the lead abatement we used a product called peel-a-way. It was a caustic stripper but it did a great job, and it was quick too. The trick with this is to wash it down with an acidic wash after you’re done to neutralize the stripper, and then wash down with water. We then sanded, primed the finish, and painted. We also used heat guns and we were quite successful. You have to pay attention to what you’re doing. It doesn’t really take to get rid of 100 years of paint and you must use a respirator when doing this though!
