Cutting Glass

[Joe Pelonio]

The latest Epilog newsletter shows on the front the story of someone using the laser to score stained glass. As a stained glass hobbyist myself I had done that many times, both rastor and vector and discovered that it worked only by vectoring on straight or slightly curved shapes. I decided that a glass cutting wheel must be scoring it more deeply or perhaps it makes more of a
cut than the laser's etch does.

So, after reading the article I tried her 35 watt settings on my 45 watt, then tried it again adjusting the speed to compensate for the power difference. Both times I got the same result I did before, it just didn't work on the more extreme curves. Those cuts, by the way, are the only ones I'd want to do with the laser, it's still a lot faster to score manually on straighter pieces than to deal with setting up a file and then the laser.
On the pic below you can see the score and where it snapped, not following the score.

I don't disbelieve the woman or Epilog, just wondering if I'm missing something.

Anyone else tried this?

[Darren Null]

I'm not really qualified to answer, because I usually make a right arse out of glasscutting...but I'm going to have a go at laser scoring now.

I've noticed my local glasscutting chaps (when I was getting a bunch of round coasters cut) score the glass, and when it's a tricky cut, they tap with the handle of the glasscutter all round the score before applying the pressure that'll snap the bit off. Presumably it deepens the flaw in the glass that you've started with the score, but it works...for the glasscutting chaps anyway. Maybe some tapping will help?

[Joe Pelonio]

I'm not really qualified to answer, because I usually make a right arse out of glasscutting...but I'm going to have a go at laser scoring now.

I've noticed my local glasscutting chaps (when I was getting a bunch of round coasters cut) score the glass, and when it's a tricky cut, they tap with the handle of the glasscutter all round the score before applying the pressure that'll snap the bit off. Presumably it deepens the flaw in the glass that you've started with the score, but it works...for the glasscutting chaps anyway. Maybe some tapping will help?
True, in fact manually I nearly cut a circle with the tapping method. The curve I tried here I can normally snap with my hands and don't need to tap.

I tried it again with tapping and it still didn't work. I suspect that my laser score is too wide/not deep enough or something. The Epilog article didn't include the dpi, I used 600. I won't try to get this on a picture, but when I compare a laser score to a wheel score, under magification, the laser is probably 4 times wider and much rougher.

[Richard Rumancik]

Joe, I'm not sure what to believe. I read about this some time ago in Laser Solutions magazine and thought it was an interesting application. It was based on a Synrad press release.

However they are cutting .130" glass with a 400 watt laser at 50 ips. I don't know how well this "scales" though. Can you cut at 5 ips with a 40 watt laser? Maybe Synrad can say if it is possible. Some materials don't scale well at all. Yet Epilog seems to be suggesting it is possible . . .

Here is the Synrad info:

http://www.synrad.com/e-newsletters/03_31_05.htm

The following picture came from the Laser Solutions article (presumably from Synrad):

[Stephen Beckham]

And I'm not talking about that Rap Song from the 90's either....

I thought about that glass piece and while I was going over that - I noticed the shine on the "glass" beer mug with the really nice frosted appearance after lasering. Got to thinking - "I wonder if that's acrylic or glass?" It sure looks like an acrylic mug the way the light is reflecting around the top. Also - I've never got my glass to frost such a pure white like the acrylic pieces....

Not trying to bash Epilog - I love my laser... Just curious about this months newsletter...

[James Jaragosky]

I seem to remember reading an article, and watching a web video on stain glass cutting with a laser. Back when I was doing all my research on my laser purchase. Anyway the article I read and watched specifically stated several times, that only some types of stain glass was suitable for laser cutting, and that most were not.
I will try to locate the web address but I’m not promising anything. I don’t toss anything away, digital or paper. So I have it somewhere. But I have so much “IT” I may not be able to find it.:o

[Barbara Buhse]

I have the same laser as in the epilog article, and I just hapen to have some 100 year old stained glass here that were practice pieces given to me by a customer... so I'm definitely going to try it, because after reading that article, all types of thoughts filled my head about some new kitchen cabinet inserts.... I'll let you know the results...

[Chad Voller]

100 year old stained glass? People collect colored glass from the early 1900's and back, broken or not. Some collector out there would cry if they heard you were cutting up that stuff for practice :)

[Darren Null]

In the Synrad article, I believe this is the pertinent paragraph:

In addition to creating the brilliant hues and colors seen in stained glass, the addition of metallic oxides or metallic salts to the glass formulation appears to alter the glass structure
...it won't go with normal glass.

[Richard Rumancik]

Darren, I think they mean that the oxides and chemicals added to "standard" stained glass makes it possible to cut with a laser; as opposed to trying to cut window glass with a laser which has no additives. I don't get the impression that they are using a "custom formulated" stained glass for laser cutting. They are just suggesting that the same chemicals that give it color seem to make it laserable.

But it's possible that one manufacturer's glass is more "laserable" than others - may take a lot of trial and error to discover what works.

Barbara, it is possible that the old glass may have a different formulation than modern glass - hard to say - but if you want to develop a procedure I'd get some offcuts of "new" glass and experiment.

I did a bit more research and can't seem to find much on the topic of using a low-power laser to cut stained glass.

Joe, you have an Epilog - why not contact them for further advice?

[Barbara Buhse]

100 year old stained glass? People collect colored glass from the early 1900's and back, broken or not. Some collector out there would cry if they heard you were cutting up that stuff for practice :)


Its already been engraved on over and over, so cutting it up won't really hurt it much more. Now that you've said that I'll make sure not to tell you where it came from. ;)

[Chad Voller]

Its already been engraved on over and over, so cutting it up won't really hurt it much more. Now that you've said that I'll make sure not to tell you where it came from. ;)

No worry, I don't collect it myself. :) My uncle's century farm is being torn down next year, and some of the relatives were going through the attic looking for anything that was colored glass, vases, wine bottles, cups, statues, even large chunks of broken stuff..... I guess they cleared them out pretty fast before anyone else could get their fingers on them.

I saw one of the broken chunks, was like a deep ruby red, guessing from 1880's. Not sure how valuable it was, but for being broken, it still was pretty.

[Darryl Hazen]

Used to work with stained glass. The way it was explained to me by an "old timer" (older than me) was that glass is actually fluid. If you were to look at centuries old stained glass the pieces would be larger at the bottom of the piece since the glass "flows" due to gravity. Using a glass cutter disrupts the molecular structure of the glass. Tapping the glass underneath extends the fracturing. If you wait too long to break the glass after cutting the molecules return to their original state and the glass will not break as scored. The laser may disrupt the molecules via the heat applied. If it were me I'd stick with the tried and true method. The colors in the glass are created by adding "impurities" to the glass during the mixing process. According to that "old timer" they add gold to produce red stained glass.

[Darren Null]

Darren, I think they mean that the oxides and chemicals added to "standard" stained glass makes it possible to cut with a laser; as opposed to trying to cut window glass with a laser which has no additives. I don't get the impression that they are using a "custom formulated" stained glass for laser cutting. They are just suggesting that the same chemicals that give it color seem to make it laserable.
The article specifies metallic oxides and salts used during the formulation of the glass. That's a starting point. I would guess that there's other methods and compounds used to colour glass that aren't metallic oxides or salts.

How to tell the difference? Presumably, different colours would be more or less useful for lasering, being made from different metals; salts or oxides. More information would definitely be welcome: glass cutting of that quality would be a skill worth having, even if it turns out that you can only do it in one colour.


Tapping the glass underneath extends the fracturing.
Underneath? My glass chaps tapped the top. Does underneath work better? Doesn't seem logical, but lots of things that don't seem logical work well.

[Darryl Hazen]

The "old timer" I was referring to was actually a member of the Stained Glass Guild in York, England. The York Minster suffered a very bad fire years ago and the huge "Rose" stained glass window was severely damaged. The guild literally reconstructed it from the pieces that survived and replaced the missing pieces. I figure if he was part of that restoration he must know what he talking about. As to why they do it that way, I have no idea. Since the guild has been around since the middle ages, there must be a good reason for doing that way.

[Joe Pelonio]

Underneath? My glass chaps tapped the top. Does underneath work better? Doesn't seem logical, but lots of things that don't seem logical work well.
I've been doing stained glass for 30+ years, though not every day, and I always tap underneath with good results. I use tapping mostly for extreme curves and some of the thicker, textured glass.

I also remember what Darryl said, about glass being fluid, and was taught to snap it immediately after scoring for that reason. That in itself seems to eliminate the laser scoring, since it could run 5-10 minutes to do all the scoring before you could open it to snap them apart. If you did one at a time it has to take a lot longer than simply doing it manually.

[Dan Hintz]

I also remember what Darryl said, about glass being fluid, and was taught to snap it immediately after scoring for that reason. That in itself seems to eliminate the laser scoring, since it could run 5-10 minutes to do all the scoring before you could open it to snap them apart. If you did one at a time it has to take a lot longer than simply doing it manually.
It's an old wive's tale that glass is a liquid at room temperature. This belief is usually attributed to glass being thicker at the bottom on old windows.

However, if you take some time to look at a number of panes, you'll notice there are quite a few that are actually thicker at the top. Plus, there is often no gap at the top of the pane and the surrounding wood, something that would appear if enough glass flowed downward to create a noticeable difference in thickness.

The truth is actually a bit less dramatic (but would appeal to the artist within us). Today's manufacturing methods typically involve huge pools of molten metals with the glass floating on top, producing some very smooth glass sheets. In earlier times, glass had quite a bit more "character". Glass artisans noticed the glass appeared slightly darker in the thicker sections, and that appeared better in their stained glass windows when placed along the bottom (even today in Photoshopped pics the shadows are typically towards the bottom). The method kind of stuck, but as can be seen by the occasional upside-down pane, it wasn't universal.

Unlike most materials that have a fairly specific melting point, glass has a large range of temps within which it remains in transition between solid and liquid. People are used to seeing glass in this range while artisans work it, even as it cools, which strengthens their belief that glass remains in a somewhat liquid form at room temp.

While I cannot say for certain what the problem is with the glass, but I believe a lower-power laser would not provide a mechanical stress crack as a physical glass cutter would. Instead, it would blast away a thin layer by melting the glass, which then is partially vaporized and is
partially redeposited on the surrounding glass. A higher power laser may provide enough localized heat to overcome the surrounding mass of cooler glass and create a mechanical stress crack by way of thermal shock.

That's my guess...

[Tom Bull]

I have been making a living with stained glass since 1975:eek:. Several things to add: gold makes ruby glass, running towards pink. It is incredible to behold. They use all kinds of rare earth oxides to color the glass, and the "recipes" are among the most valuable assets a glass manf. can have. I went to a glass factory to get a special color duplicated for a repair. They matched the color to the master set of glass and then went into a vault, opened a safe, removed a fire-proof box, and in it was a ledger book with all of the formulas they use dating back to the 1880's. They used to supply some glass to Louis Comfort Tiffany. It was very cool.
Their is a lot of controversy about whether glass is a liquid or not. Today's wisdom is that it is not.
As far as tapping the glass, yes it works. If you don't tap directly under the score mark your glass will "flare" in the direction of the impact. (Two keys for succesful glass cutting: use the proper downward pressure and lots of oil, like 3 in 1, on the wheel, or as when we cut heavy plate put the oil directly on the glass).
I have heard a lot of people say that a score mark will "heal", but I have broken a lot of glass that was scored days or even weeks later.
Being from Missouri (the Show-Me state) I couldn't believe that the laser score would work, but my preliminary test on a piece of Kokomo Opalescent glass was amazingly good. I scored the glass and it practically fell into a circle. More testing to come.
Anyway, once again the Creek is great reading.

[Michael Kowalczyk]

Not sure if this will help any but I use my Tivo to record every "How it's made" and a some other "How they make it" programs and one of them had a segment on making windshields. They used a laser to cut out the various shapes. I have no idea what the power or speed was but it was cool to watch.

[Stephen Beckham]

YEA - what Dan said... :confused::eek::rolleyes:

[Peck Sidara]

Stephen,

The beer mug is definitely glass, not acrylic. The style from Sample Club (and about a million others) can be purchased here: http://www.discountmugs.com/usa/glassware-g-57c-flare-glass-mug.htm. To get that frosty effect, our mar-comm specialist used a thin layer of dish washing detergent and went through several glasses to get the right settings.

Joe,

Richard said it best: "It's possible that one manufacturer's glass is more "laserable" than others - may take a lot of trial and error to discover what works."

Many of our customers use our systems in unique and innovative ways. Needless to say, when someone thinks they've stumbled upon a new application for the laser, they're not always eager to share all the details. I can't say I really blame them. The stained glass application definitely has a lot of potential, so unfortunately at this time, the manufacturer in the latest "Customer Spotlight" was not named. We're currently testing various glass sheets in an attempt to find the right combination. We'll make sure to pass on our findings as more information becomes available. The customer spotlight section and other case studies are meant to inspire our customers - to give them creative ideas and applications to test on their own. While we certainly want to get all the information we can to pass along, we have to respect our customers' right to keep some information private. In this case, please rest assured that scoring stained glass is indeed possible - the challenge will be finding the stained glass material that works best in your laser.

[Joe Pelonio]

Stephen,

Joe,

Richard said it best: "It's possible that one manufacturer's glass is more "laserable" than others - may take a lot of trial and error to discover what works."

Thanks Peck. When I do stained glass work, I most often choose the more textured multi-colored (and expensive) glasses, probably will not score well by laser. At $25/sf I can't afford to do too much experimenting. I think the example was probably mostly transparent 1/8".

This dragon piece is about 18"x24" and has over $150 in the glass alone.

[Peck Sidara]

That's a very nice sample Joe.

[Chad Voller]

It's an old wive's tale that glass is a liquid at room temperature.

http://math.ucr.edu/home/baez/physics/General/Glass/glass.html

Read this. There's no evidence pointing accurately in either direction (if all glass types flow or not depending on composition and crystaline structure). But it is more towards it being solid. One thing to consider is when scientists slice organics very thinly for microscope observation, they use a fresh piece of fractured glass, which is sharper than the sharpest scalpel. If they don't use that fractured piece of glass within a day or two, it is no longer sharp enough to make accurate cuts. (saw this on the Science Channel) whether or not this makes it a slow moving fluid, still confuses scientists.

[Bill Cunningham]

I thought about that glass piece and while I was going over that - I noticed the shine on the "glass" beer mug with the really nice frosted appearance after lasering. Got to thinking - "I wonder if that's acrylic or glass?" It sure looks like an acrylic mug the way the light is reflecting around the top. Also - I've never got my glass to frost such a pure white like the acrylic pieces.

A lot of the nice white look, comes also from what you have in it to provide the contrast.. The one below looked pretty good dry, and when filled with beer, looks great.. Until it's empty, then darn it.. you have to refill it again.. It's a vicious cycle I tell you!!!!

[Stephen Beckham]

Peck,

Thanks - I trust your word - Feeling stupid, I looked back a couple of my pictures to see that my photos give the same glare from the glass. I also noticed that when my pics had flash used in it - I got a higher frosting look.

Take care...