Engraving leaded glass

[Dan Hintz]

For all of the posts I've read, there did not appear to be a true consensus on if lasering leaded glass was wise. The opponents seemed to believe the higher lead content in the glass led to greater expansion and shattered material, whereas the proponents felt the difference in expansion was minimal and caused no more shattered material than any non-leaded glass (assuming the material was not overpowered).

I have the potential for some serious orders, but they would be using leaded glasses that are quite pricey (pairs of glasses being in the $50-$350 range!). I don't want this to be a discussion about charging high prices to mitigate my risk should one break, I want to focus strictly on capability. Thoughts?

[Michael Hunter]

When researching which laser to buy, I was told by the UK Trotec dealer - "Don't even think about engraving crystal : the lower quality the glass, the better it engraves". This from the man who wanted to sell me a £25000 machine!

My understanding is that the lead content of crystal makes the glass semi-transparent to the laser beam : beam energy gets inside the glass and explodes it.
Ordinary window or bottle glass is opaque to the beam, so the action is only on the surface.

I must admit that I have not tried it myself (lacking the nerve and also a rotary attachment).

[Martin Boekers]

I've done crystal bases without issues, although a glass is a bit different.

My first concern is laser etching quality going to be acceptable.

I would show some samples as the client may have only seen sand etched and those are completely different in quality and detail.

Marty

[Richard Rumancik]

Personally, I would not try to laser an expensive piece of leaded glass. The laser etches glass by heating up the area causing rapid expansion and a small fracture. You wouldn't be able to charge enough to be able to recover a few $300 rejects. I think sandcarving is really the way to go. If the designs are one-of-a-kind then maybe the laser can be used to make masks, but if it is a production job (all the same) then it would be less expensive to go with conventional masks.

It is also possible that you could leave residual cracks that may cause the crystal to crack some time after lasering, initiated by a small bump. Just like a chip in a car window - it may be dormant for a long time and then suddenly a temperature change or minor jarring could cause the crack to propagate.

Sandcarving is an abrasive process and it does not leave points for a crack to initiate.

[Dan Hintz]

Michael, I always have to questions statements like your dealer's (as I'm currently doing) as I have been unable to have anyone back it up with facts and/or experiments. Had the dealer tried it before? Did any of his clients try it, and if so, did they try more than one or stop after glass #1 broke? Too many open questions like this lead me to believe it's bordering on a wive's tale started by someone who either had a bad glass or didn't know how to mount it gingerly in the rotary. In regard to the "cheaper is better" comment I hear everywhere, could it be that a higher quality/cost glass is also more fragile by nature? Look at the rim thickness on a dimestore glass versus a quality one... 1.5-2mm vs. <1mm. It would be easy to break the good stuff by looking at it.



Martin, the laser is being targeted here due to quick turn-around and verying designs from one batch to the next (personalization), so the difference between sand-blasting and laser-etched is a known quantity. Personally, I like the laser-etched because it's so smooth after the fact, but that's just my opinion.



Richard, your explanation is much closer to a scientific (or at least experiment-based) explanation that I'm after. That said, the argument could be made just as easily that the type of etching (fracturing versus abrasion) could just as easily leave a cheap glass open to breakage... quality or cheap, glass is a crystalline structure, so no matter how thick it may be a fracture in the structure will propogate through it. Using that 10,000 foot view of the process, a cheap glass would break just as easily... but we all know they hold up extremely well.



I cringe at doing so, but it looks like I may have to bite the bullet and try out some excruciatingly expensive tests :( If anyone else would like to add in their thoughts before I take out a mortgage on the home for an experiment, I'm all ears :p

[Richard Rumancik]

. . .Richard, your explanation is much closer to a scientific (or at least experiment-based) explanation that I'm after. That said, the argument could be made just as easily that the type of etching (fracturing versus abrasion) could just as easily leave a cheap glass open to breakage... quality or cheap, glass is a crystalline structure, so no matter how thick it may be a fracture in the structure will propogate through it. Using that 10,000 foot view of the process, a cheap glass would break just as easily... but we all know they hold up extremely well.


I think you may be correct that cheap glass could also fracture. But scrapping out a $5 piece is a bit more acceptable than scrapping a $150 piece. You might not find exhaustive studies on the subject, as few people are eager to do the experimentation. It does not have industrial applications so you don't find much info from companies like Synrad.

There are also different types of crystal (varying amounts of lead oxide). And you might not always know what you have been given. If you want to experiment, I would look for some inexpensive crystal paperweights or trinkets, but try to find something that has the lead oxide content specified. That will also demonstrate the appearance of the etching as well, so that your customer has a better idea of what to expect.

[Scott Shepherd]

The Rayzist (sp?) products look to me to be perfect for this application. I would think the laser would be the slow way to go on this one, depending on how much area is engraved. You can easily personalize the masks. It's nothing more than printing the graphic these days and you have to make the graphic for the laser anyway, so no real difference. Only difference is you have to expose the film, which, from what I saw, can be a easy job done in batches.

[Jim Unsworth]

I've done crystal bases without issues, although a glass is a bit different.

My first concern is laser etching quality going to be acceptable.

I would show some samples as the client may have only seen sand etched and those are completely different in quality and detail.

Marty
With glass it is all rather simple. Dollar Store or inexpensive glasses have more air bubbles than does leaded glass. These bubbles explode on contact with the laser's heat causing the glass to fracture in a thousand places giving that frosted look. This shardy residue must be rubbed off with with a paper tower to make smooth. If you are a perfectionist and have the time apply wet newspaper to the area being lazed. This will give you a softer edge on your graphics.

[Randy Walker]

Hi Dan
I don't know the first thing about lasering leaded glass, but I do know that I would find a cheaper scource to experiment on. Try some of the local auction houses. They may be able to put you in touch with antique dealers that are willing to part with dammaged, broken, or partial sets of otherwise very good crystal glasses, at bargan store prices. A web search of some on the makers or brand names may get some message boards (you already know what to do there). Go to garage in some of the higher end comunities. I have been amaized at some of the expensive things I have found for cheap in my trips to those area's. I'm sure there other places to try too.

Hope that helps

Randy Walker http://www.sawmillcreek.org/images/icons/icon10.gif

[Bill Cunningham]

There is enough aggravation in work, without having to tell a customer that their 300.00 glass fractured in the laser.. I would back right off, but if the customer accepts ALL the risk (other than maybe a spelling mistake that 'you' make) Write something regarding fractures on the sales bill, and have them sign it. Then, give it a go.. The only glass I have ever had fracture in the machine, was a oil lamp globe.. It was pretty thin, and I think I hit it much harder than I needed to back when I first got the machine (remember the laser everything but the cat faze? :D) I recently did a champagne flute where the etch did not frost at all, perhaps the cause was lead content!