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solvent-based removal of old window putty

Posted by slateberry51 (My Page) on
Tue, Nov 15, 11 at 11:34

So after all the reading and thinking and hemming and hawing (yes I've over-analyzed yet another project!), I re-glazed my first window. I used oil-based primer and Dap 33, and it went reasonably well. I told dh, the glazing was easy, it's the prep that was killer.

The single hardest thing was getting the old glazing out. Looking around at options, I've seen physical and heat-based options:

Prazi drill bit
dull chisel and 5-way tool
heat gun (20% glass breakage or more)
steam and heat softening (John Leeke's video, he claims 4% breakage)

What I wondered was, what about a solvent-based option? But what would dissolve old hardened glazing? Turns out, old hardened glazing is basically dry linseed oil and lime that has more or less turned back into limestone (OK I'm hedging there, but that's my best info.) Apparently the solvent for dry linseed oil is....linseed oil. And the solvent for limestone is...bleach? I'm not so sure about the second one, but I trust the first one.

So, I'm going to test this out and report back. But I just wanted to share what I've found with the forum in case anyone else has already tried it.

Follow-Up Postings:

RE: solvent-based removal of old window putty

I took out 36 panes of glass over the last week with a heat gun and only broke one pane; but not from the heat gun.
A couple of years ago I took 23 stained glass panes out of my kitchen door with my heat gun (and now that I understand why the putty was as hard as stone...) and didn't break any.
It depends on how careful you can be.
Not that I haven't _ever_ cracked a pane from heat because I have, many times, but you must learn and improve your technique. My average doesn't come close to 20%. If you are breaking 1 in 12 it's too many.
You must have a heat gun where the temp. can be regulated, like the Makita gun, the temp is electronically controlled.

RE: solvent-based removal of old window putty

"Apparently the solvent for dry linseed oil is....linseed oil."

There is no actual solvent for linseed oil that has polymerized.
It must be broken down, nit simply 'dissolved.'

RE: solvent-based removal of old window putty

Casey, thanks for the encouragement--you're right, experience is the best teacher. I should just jump in.

Brick, that's bad news. Stinkin' polymers.

Guess I'll be getting a heat gun for Christmas this year.

The good news is that I pulled some old windows out of the trash that turned out to be too small for replacement glass for my windows. But they'll be great for practice.

RE: solvent-based removal of old window putty

I use a 'putty chaser' in a drill, or even a small router (laminate trimmer type) with a top bearing and carbide edges.

It is not fast work, but does minimal damage.

A board about 6 inches wide is clamped to the window with the edge aligned with the muntin.
The router bearing than follows the edge of the board and is held barely 1/16 inch off the glass (this avoids any flat push points holding the glass in place).

Sometimes the muntins are aligned well enough pane to pane you can do a row of edges before moving the wood.
You need to be careful at the corners to remove as much hardened putty as possible without cutting into the wood.

The thin leaving can be removed, then the glass removed and any remaining putty used for bedding cleaned out.

Offset chisels and a small 'bruzz' chisel (inside corner) help things along.

RE: solvent-based removal of old window putty

Thanks for the details on the physical removal. I have both a router and a corded drill (don't think I'd want to use cordless for this), and while I really like the concept of that method, I've shied away from it because out of all the options, it seems to me that one would generate the most lead dust. I have my eye on a Milwaukee variable temp heat gun, hoping that I could get it hot enough to soften the putty without vaporing the lead paint. I don't know, it seems there is a downside to every method, but one way or another, I'm keepin' my windows!

If I worked outside on a tarp in a tyvek suit and disposed of the suit and tarp properly after a work session, do you think that would be a responsible way to deal with the dust generated? I mean, most of it would be from the putty, not the paint on the putty, but there would definitely be some lead dust generated. I think given that I have 3 kids, doing this inside, even in the basement, would be out of the question. It's a tough call. But I'd like to find a way to try it responsibly.

RE: solvent-based removal of old window putty

The Speedheater and similar products are designed to keep the heat below the point at which the hot paint produces lead fumes. You can shield the glass with an aluminum foil covered piece of masonite. There are some videos at

The Speedheater site may be slow to load, because it has a video on the home page.

Here is a link that might be useful: Speedheater

RE: solvent-based removal of old window putty

Yeah I've had my eye on a speedheater for a while. I get to borrow a friends the week between Christmas and New Years, so that should make for a pretty festive week. Maybe I'll hold off on getting the milwaukee 8985 until I've tried that. I'd hoped to use the milwaukee gun at one of the lower settings and thus avoid the lead vapors, but maybe I should focus on getting an IR stripper instead of both that and a variable temp heat gun. I mean, if one device can cover all the bases, why get both? I'm thinking of building my own IR paint stripper. Dh is an EE, so he probably won't let me electrocute myself if I behave.

Here is a link that might be useful: DIY IR paint remover example

RE: solvent-based removal of old window putty

TOH just ran a piece on the same subject. Norm went to a company that rebuilt old windows. I believe they steamed the windows to remove the glazing and paint.

RE: solvent-based removal of old window putty

Olde Window Restorers has a brief video showing steam paint removal:

Here is a link that might be useful: Portable Steam Paint and Putty Stripper

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