Removing a Pane of Glass

[hugh]

I want to remove a pane of glass from the French windows to install a cat flap. I've taken out the beading and the external putty. Are there any tips on how to remove the glass without breaking it?

[Cash]

Unless the putty [1] is recent - you won't have a "cats chance in hell" of removing the glass without breaking. ;-)

The simplest way to do this job is to put a dust sheet down, slip on a pair of leather gloves (and goggles if you wish) and then work a flat bladed scraper (or broad knife) between the frame and glass and lever out the glass. It will break, but usually into large, easily disposable pieces rather than shattering - as when the glass is hit by a hammer etc.

Note: Keep an eye out for the odd shard of glass that will break away and fly off into the distance - hence the dust sheet.

[1] Presuming that a back-putty has been used.

Cash

[Dave Liquorice]

Probably but if you take your time and work around easing the thin blade in with not lvereing the glass may come out. Make sure you have removed any pins holding the glass in that where covered by the bead and that there is nothing sticking out from the side of the rebate that could stop the glass coming out.

[Andy Dingley]

I do a fair few of these, as I install stained glass panels for a friend who makes them. I want the glass out and the frame cleaned with the least mess, even if I don't care about the glass.

Leave it in place and cut it for the flap in situ. It might work, it might not. It's not much harder than cutting this old glass on the bench. It's likely to fail because the glass is old, not because it's still in the frame.

Old blanket over one side, score into 6" squares, hit with hammer. Replace glass afterwards.

To try and extract it, you need to take all of the putty out, all of the small brads, then unstick it from the putty bead behind. I use my MutleyMaster for this, along with a few sharpened 3/4" Chinese chisels from Lidl (I can hammer them through brads without shame). Finding the last brad is always a nuisance - a stud detector might help. Usually they're rusted and snap rather than pulling out, but they snap flush or can be punched down.

The time you'll break the glass is when you bend it trying to unstick it from the back. You need an assistant on the other side to catch it, thin paint scrapers etc to pry it free from the inside - the MutleyMaster can be handy too, as can a plastic scraper - and you'll soon learn just how much glass can flex before it breaks. Sadly that's probably followed by how much it can flex immediately before breaking.

I'd cut the catflap in situ.

[geoff]

In message , hugh writes

you might be lucky

it depends on whether it's stuck to e.g. putty on the other side, doesn't it

Why do you want to remove it intact?

Do you intend to try and incorporate the cat flap in the old panel, or replace uit

I would get some 2" packing tape and cover the glass so it holds the pieces if it does break

[Dean Heighington]

Or... Get rid of the cat ;)

[Matty F]

It's not easy but with care it can be done. I have removed 36 panes of glass from 150 year old windows so that I could repair and paint the frames. I broke a few panes. I wanted to retain the old wavy glass for heritage reasons. I had a spare window so didn't need any new glass.

[DavidM]

As Harry said, you'll almost certainly not be able to cut the old glass, either in situ or if you manage to get it out in one piece.

Get a new piece of glass from a local glass supplier and get them to cut the hole in it. Take the cat flap with you so that they can check the size - their problem then if they get it wrong! Far quicker and not very expensive.

[Newshound]

What everyone else said, plus while it shouldn't work in theory, even old putty softens to some extent with judicious warming from a gas torch or hot air gun.

[docholliday]

I've done that, too, though not on such a large scale - some of the panes were etched obscured glass and some were coloured, so I wanted to keep them to match the ones in other windows. If the putty is _really_ old it may have hardened and lost adhesion, which can help you - the large bead of putty on the outside, which is relatively easy to deal with, may well have been replaced, but the bit between the rebate and the glass probably won't.

[Matty F]

Except that the OP didn't say that he wants to cut a hole in the old glass, which is usually impossible without the glass breaking.

[hugh]

No what I've done previously in a similar situation is to fit the cat flap into a piece of plywood cut to fit in place of the glass.

[Thomas Prufer]

You may be able to loosen the glass by getting a block of wood, placing it on the glass and hammering sideways -- hammering so you're tapping in the direction of the surface of the glass. This may flex the frame sides enough to break the bond between the glass and the putty, and the glass is less likely to break as you're loading it along its plane, not bending it...

Thomas Prufer

[hugh]

That sounds interesting. I think I'll try that first. Thanks to everyone who responded.