cutting mirror glass

[bent]

I can't say I'd even know how to cut regular glass, but I've got some mirror glass to cut to about 11x20". Its from a $11 cheesy wood framed ~16x24" new mirror. I measured it at .081" = ~2mm thickness. So there are inches on the sides to cut off. I've bearing-rabetted out 3/8" around the inside of a

1x2" frame I made. Theres about .2" left to the front face I'll paint. I'm gonna back it with 1/4" Birch plywood, and brad it in w/ 1/4" 1/4 round (.500"Diameter).

1) should I worry about the birch ply right up against the mirror paint? Its not pictures.

2) Should I score the back side where the mirror paint is. Or grind it, or get through to the glass somehow, whether straight or not. Theres ~3/8" to the max edge on each side, so I could make a mess of the finish, I think, without affecting the view from the outside.

3)I am assuming no matter what I am going to do I need to score on the glass side

4) When scoring it says to score with one line only. How hard do I need to push? I just bought a $5 "6 wheels" Richard cutter. Then push down (away) from the cut line on the corner of a table?

[tom]

Unless it's tempered, from the top (glass) side, make_one_ firm score along your desired cut with the aid of a straightedge. Then take the ball end of the cutter and, starting at one end, gently tap along the bottom (mirrored) side of the score. Take your time. You might still break your glass where you don't wish it to break, and them's the breaks. Tom

[RicodJour]

You need to seal the cut edge of the mirror so moisture (read humidity) doesn't get under the silvering. Otherwise you'll get the black tarnishing working its way in from the edge.

The back of the rabbet will be reflected by the mirror, so its typical that the rabbet is painted black so the reflection won't be distracting.

I don't understand what you're asking. Why would you need to score the back side of the mirror? You always cut from the face. No need to touch the back.

Right.

You're just scratching the surface of the glass, so you don't need a lot of pressure. You can practice on a glass bottle to see how hard you have to press. The cutter should be lubricated with kerosene and it will sing if you're using constant pressure. Keep the movement uniform and unbroken.

Work on top of a towel so you won't scratch the mirror, and snap it on the edge of the table like you mentioned.

R

[bent]

Then take the

do I need a soft (say towel) to pressurize under while doing this?

do I need also to flip it back over to snap it off in one piece.

not sure i'm clear on this method, or part of a method

[bent]

How can I do this. Can I use a paint? or a tape? Polyurethane? Sounds important!

I will have a lot of white going on around . Does this work, or should I do black too?

The cutter should be lubricated with kerosene and

I don't have any kerosene. Is lube a must? What about anything else I have, say, methyl hydrate, lacquer thinner, mineral spirits, gas (w/ fill-up), TSP solution, brush cleaner, other?

do you suggest any cracking or prep before a final snap?

[tom]

No, let the cutoff hang over the bench, and tap from below. Oh, and wear safety glasses.

No. A good break will come off as one piece.

[bent]

how can I be tapping along from one end and a good break will be one piece. Isn't a tap gonna produce a break, which will be either one piece, or a bunch of pieces. Break little pieces, but try to break one piece? Don't break?

[bent]

can I just align the score op top of a 1x2" edge and PUSH down, to snap on one piece?

push down firmly against the score until it gives?

I don't want to learn breaking glass. I am looking for my best bet, or I'd take my Richard back. But I took apart the frame so...

[Guess who]

Maybe I'm wimpy, but I've wound up with so much broken glass, I take mine to the local glass experts. They don't mind even if I bring my own, and the cost is minimal ...and expertly done. They do the glass. I do the wood. Sometimes I buy the mirror/glass from them for projects. I definitely let them cut the ovals.

[Michael Daly]

Don't put the glass on a towel - if you push hard and the towel is soft enough, you'll break the glass. You might get away with it on thick glass, but the stuff you have is very thin.

Use a _flat_ surface and make sure it's clean - no junk under the glass.

When you score the glass, you create a stress concentration along the score. When you tap the glass with the little hammer, small cracks emanate from the score in various directions - mostly through the glass. When enough of these cracks propagate and connect, the glass breaks clean along the score line. When you look at the edge that results, you'll see the uneven surface that forms from all these little cracks. You can sand the edge with fine, hard sandpaper to smooth the edges.

Wear gloves and safety glasses.

Mike

[James "Cubby" Culbertson]

I'm no expert on cutting glass, so I take it to my local glass supplier and they cut it for me. They usually don't charge me cause they know I'll be back to buy eventually. Cheers, cc

[George E. Cawthon]

[George E. Cawthon]

[George E. Cawthon]

Yes!

Yes. Use a glove.

[Pop]

Interesting thread since I've been trying to get around to doing the same thing but on a thicker mirror (float glass). But even after reading the whole thread, there seems to be two conflicting paths to accomplish it, both of which I already knew, and neither of which has ever really worked for me. In fact, some of the posts sound like guesses based on having cut some plexiglas once, but ... I'm too ignorant on the subject to know if they're right. And, if "tapping" isn't right, why does nearly every glass cutter sold come with a ball shaped on the opposite end? Guess I'll go Google.

Pop

[no(SPAM)vasys]

For cutting curves "tapping" with the ball end is appropriate. For a straight cut it is easier to snap the glass over a straight edge.

[RicodJour]

The ball end glass cutters are very common, but there are lots of choices and many of which don't have the ball. The ball is an attempt to make the tool one size fits all - a multipurpose tool. For cutting small curves, the ball end can be useful for tapping to propagate the crack. That shouldn't be done on mirrors as it could damage the silvering.

If you've ever been in a commercial glass shop, you'll see that the guys have a carpet covered table and snap the glass over the edge. It's way faster and less likely to have the glass break due to an imperfection that you'd never see. The microscopic imperfections are the weak points in the glass. Tempering is just a way to let the molten glass fill in those surface imperfections - that's where all of the increased strength comes from. It's not special glass.

Whether the glass is thick or thin, the same uniform score is sufficient. If you've ever seen the 1" thick glass used in some church windows, that's how it's cut. They score it, pick it up with a hand on either side of the score line and drop/push it down over a hard plastic edge. It breaks just about as easily as the standard float glass you have in your window.

To propagate the break along a score line glass artists (like myself - I do stained and leaded glass work) use running pliers, which are basically pliers with a curved mouth or ridge in the middle of one jaw. Gentle pressure is all that is necessary.

Another technique is to put a wood dowel under the score line and snap the glass over that. There are many techniques for glass, and everyone will swear that their system is the best. Basically it boils down to trying different techniques until you find something that works for you and gives you good, repeatable results. That's when most people stop trying different techniques because they've found the "perfect" technique.

R

[Jerry]

Do what I did and just go to your local mirror / glass guy. I've done that a number of times. Only charged $10 for a cut job bigger than yours. One broken attempt will pay for this service.

[gfretwell]

I'm surprised you didn't mention, the glass has to be clean and you lub the cutter with mineral oil. ;-) I like the pistol grip cutters with the resivoir in the handle. I am not an artist yet but I do stained glass too. I cut on heavy cardboard, over a very flat counter top.

[Larry Jaques]

On 5 Mar 2006 19:45:28 -0800, with neither quill nor qualm, "tom" quickly quoth:

Nearly every glasscutting book I've read has said that the ball end of the cutter will shatter more glass than it helps score, so don't use it. My experience prior to reading them (33% loss) mirrored theirs. (bad pun intentional.) I don't cut much glass, but I haven't lost a piece of glass since buying a set of running pliers.

I suggest setting the mirror on kraft paper a super clean piece of MDF or other flat table. Score it on the front, move that score line to let the scrap overhang the table, using either glass running pliers or a quick snap to break off the glass scrap. Some silver protectants are plasticized so if you also score the silver on the back, it has less of a tendency to pull off any silver at the cut edges when you break the scrap off.

Also remember: NEVER run the carbide cutter over a previously scored section of glass. It instantly dulls the edge and makes a rough cut which can shatter and run away from you. DAMHIKT. ;)

-------------------------------------------------------------------- The more we gripe, *

longer God makes us live. * Graphic Design - Humorous T-shirts