All christmas is 40% off this week anyway…and yes…I always use the coupon…we have three Hobby Lobbys with a close range so many times I use the coupon at all three😏
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I’ve sandblasted them and they worked well - only once did I blast through one…was actually funny since I was engraving a name and suddenly it was "clear"I was trying to "blast"it thinking that my gun was jammed (no grit coming out). Apparently I had gone right through the glass - oops.
As far as lasering through to the bottom - it would be easy enough to but something inside. You could cut out the shape of the ornament in paper and roll it up to fit inside then it would “unroll” yet still should be no problem to pull out. Fill it with beans or rice to block the beam (if that is even an issue.
I’m still bummed Hobby lobby no longer carries the flat glass ornaments shaped as circles, heart, bell, etc. They only carry the ceramic/plaster ones now ( 2 yrs ago they carried the glass/crystal ones).
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As far as the 10600nm laser light is concerned, “glass” is opaque. There are some materials that are transparent to this wavelength of “light”, and those materials might sorta look like glass, but I doubt anyone would make $1.50 ornaments out of it.
I looked for a transmissivity graph showing many kinds of glass, but most of the ones that I found seemed to cut off at 2500nm. Here’s one exception…
(1 micron = 1000nm)
Source: https://rayotek.com/techincal_info_glass_sapphire.htm
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Sweet…looks like it may not be a problem.
I’ve done wine glasses and mugs on the rotary without the beam affecting the otherside. Those had a minimum of 2.5" in between the two sides. These ornaments are much narrower and thinner so wasn’t sure.
Now its a question of fragility since the laser actually microfractures the glass as it etches.
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These “cube” ornaments come up as “frequently bought with” at 1.75" they should squeeze in the GF also.
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Thanks, I didn’t notice that they had ones this small. Should also fit with tray removed. Can’t remember about focus that close though.
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With the tray removed you should be able to focus on anything 1.5" to 2" tall just fine.
EDIT: Also anything up to .5" with the tray in.
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Can confirm that just about anything you’d buy that’s sold as glass will look like a brick wall to your laser. 
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does the camera autofocus have any issue with a transparent substrate?
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the beam focuses on the surface of what ever it is engraving the rest of the ornament will not be marred . however if its cheap glass it may crack while it is being engraved. experience taught me that one
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Nothing like the voice of experience. 
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I can’t speak for the glow forge don’t have mine yet but I usually manually focus transparent and anything curved so there is no accidental chance of the head hitting the object if it mis focuses.
Update…I bought some colored ball ornaments that I put on my rotary…seems they were covered in some metalize material…tried to raster off the top layer like I do with my colored aluminum drink cups, but havent gotten the settings correct yet…so I’ll keep working on it…although its not useful info since they won’t fit in a Glowforge anyway…
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I’d love to know if you get it right and what settings you used and the ornaments as well
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The standard practice at our local Makerspace is to apply a thin layer of dish soap to the glass surface to be etched. Supposedly reduces fracturing, but I’ve never tried without it.
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I got some round clear ones to experiment on getting a good coat of color on the inside. Didn’t want to waste the flat ones in case the methods I try don’t work out. Once I find a good method of coloring that looks like it won’t crack off, I’ll be preparing the flat ones for lasering. I’m hoping that a coating inside will set off the lasered graphic when I can do that. Will rinse the inside with alcohol to clean, then try acrylic paint, floor polish with glitter, floor polish with some acrylic paint to see if that bonds better than just the paint, alcohol ink, and even floor polish with some food coloring tints.
Trying floor polish because videos seem to show that it really works good with glitter, but I’m not sure the lasered graphic will show up well on glitter.
Will report on this soon.
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I haveen’t tried the dish soap method yet, I don’t know why not though. Lots of people say it’s the way to go.
I have used wet/damp newspaper a couple times and it works quite well. So does the sticky paper masking material (dry).
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If laser is like sand blasting ( probably looks the same) on glass ornaments, it doesn’t really show up that well with the glitter inside (btw the floor polish and glitter works great - acrylic paint works well - don’t even need too much and you can “marble” it if you add right and keep turning it. I used rub n buff on the engraved area - looks great and easy to apply - doesn’t adhere to the untouched glass. Was hard to get a good pic…
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I’ve heard that but I have never used it. The only time I have had a problem is with really cheap glass that probably was not annealed properly. I’ve been told that the dish soap will case just enough surface tension it will hold, which is kind of funny since in water it breaks surface tension.
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Yes - it’s designed for an opaque substrate, like a protective coating.
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