solvent-based removal of old window putty

slateberryNovember 15, 2011

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.

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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.

    Bookmark   November 15, 2011 at 3:52PM
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"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.'

    Bookmark   November 15, 2011 at 4:36PM
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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.

    Bookmark   November 15, 2011 at 9:28PM
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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.

    Bookmark   November 16, 2011 at 9:57AM
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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.

    Bookmark   November 16, 2011 at 3:14PM
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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

    Bookmark   November 16, 2011 at 6:03PM
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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

    Bookmark   November 17, 2011 at 8:14AM
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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.

    Bookmark   November 17, 2011 at 7:40PM
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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

    Bookmark   November 18, 2011 at 12:22AM
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David Stembridge

What temp is ideal regarding use of a heat gun? Trying to decide which one to get.

Did anyone have success trying to soften old glaze using linseed oil?

    Bookmark   September 17, 2014 at 12:41PM
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Since this thread has surfaced again, I want to add that in the interim I worked on a very big re-glazing project, over 500 panes, some quite large old irreplaceable glass, and what I eventually came up with was water+ heat gun = targeted steam right between putty and wood. I scored along the glass/paint/putty boundary with a razor blade, as one does when cleaning paint spatters, but actually being aggressive about exposing the edge of the putty. Then washed the sashes with hot water and detergent. I then proceeded with the heat gun at a #2 setting (5 being the hottest on the Makita guns). I was able to get a 10-pane sash de-glazed in 20 minutes this way, with no breakage from heat. I wish it had occurred to me earlier that the water heated with the heat gun would pop the putty out like it was nothing.

    Bookmark   September 17, 2014 at 3:59PM
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David Stembridge

@sombreuil_mongrel How did you heat your water, and how did you apply the water?

    Bookmark   September 17, 2014 at 8:59PM
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Casey, um...EUREKA!!! I can just picture it. Can't wait to try it. Thank you so much for sharing.

I wish I could say I'm going to jump right on it, but the schedule is getting tight this fall...because I'm applying to school to go for my MArch! Wish I had time to commute to Roger Williams, but I'm sticking to Boston-area schools in the hope that I'll still get to see my kids once in a while.

The funny thing is, there are so many great posters on gw, it actually discouraged me from applying. But out in the "real world", I meet many far less-knowledgeable and less-focused people contributing to society just fine in their chosen fields, so I figure, what the heck, even if I'm not the most talented, go for it.

Originally I was going to wait until the kids were grown and go to the classical architecture program at Notre Dame, but I decided I just couldn't wait that long to further my own career. But that would have been SO cool.

OK, definitely OT, but had to share Casey, bc you are one of my heroes. If I can get half as far and contribute half as much in my field, I'll consider it a smashing success.

    Bookmark   September 18, 2014 at 6:30AM
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OK, BTW the water was warm, like from a August-solar-heated garden hose! Don't sweat it. It's more important that you have a temp-controlled heat gun like the Makita, where a thermostat cycles the heating element on/off to maintain a steady temp, and don't go above 2 (I keep it on the low side of 2) and that is still hot enough to break glass if you train it in one spot for too long. Always move the gun forward, away, elsewhere every few seconds. The steam works, and you don't have to buy an expensive, messy steamer if you already have a heat gun.

    Bookmark   September 18, 2014 at 10:04AM
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David Stembridge

Thank you Casey! Will be trying that on my ol' 50s windows!

    Bookmark   September 18, 2014 at 10:54AM
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A couple more tips. the older the putty, the longer it can take for the water to make its way in between; The easiest is putty with lots of cracks. For putty that is sound, but old and hard, I advise laying the sash down on a flat level support, and filling the pane recesses/wells with the water for a few minutes, so it gets as deep as possible.
The more water the greater the chance that the interior paint may be disturbed, but it is still a lot kinder than putting them in a steam box, which will wreck the interior finish entirely.
Hope it works as well for you as it did for our big project.

    Bookmark   September 18, 2014 at 12:17PM
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