I have found that contrary to all advice here the only way to get most glass to engrave is to use about 4 times the power that shows a good mark.

I always get some edge fracturing, really small but not up to my quality levels. It also left fragments that you could not see but would stick in your fingers. I did a test of the higher power after trying every piece of advice. It gave me a nearly sandblasted result with no fracturing. When I say nearly sandblasted result I mean that glass was removed and a blasted look was achieved.

Philadelphia, PA (Really Bensalem)

Harvey's Tips Page When you finally understand it completely... it changes.

When you bump up the power, do you still use a wet paper towel? Can you share a power setting, speed and wattage? I will try it to see if I get a quality comparable to blasting.

Thanks!

I don't think you can get a quality comparable to sand carving. At first I was very happy with just the laser on glass (and still am for photos), but after getting a small blast cabnet, I don't offer straight lasering any more. I always follow up with the sand blaster. There is just no comparison to me.
Bob

Harvey,
I use 100p 40s 300ppi 3ID and process the photo in PhotoGrav. The picture here is really a bad representation of what it looks like in person, but gets the point across I think. I do photos on glass fairly often, but I always sand carve everything else.
Bob

If that is a bad representation, I'd fall off my chair seeing a good one.

Your power settings are close to mine. Very interesting.

I am not sure what 3ID is, is it a diameter?

Apparently 300 PPI, (reduces the DPI to at least as low as 300), is a good value for glass.

Philadelphia, PA (Really Bensalem)

Harvey's Tips Page When you finally understand it completely... it changes.

To reiterate, I now laser at 1000 dpi. 100% power through signwriters application tape on glasses, then sandblast lightly using the application tape as a mask. All with a 25watt GCC Mercury.
It's the only way I can achieve consistent results on glass with the laser as I find that glass varies so much.
Also easier than photo-resist. The application tape seems to conform to compound curves reasonably well, and the resulting work tends to be consistently straighter round the glass than photo resist or vinyl.

Harvey,
ID is image density (same as DPI) (I have a ULS M-360, 40w). Glass seems to work best at a setting of 3 with the PPI set at 300. Like I said, I can laser photos with this, but the lettering and other non-photos I very much prefer blasting.
Bob

Ken,
I do spray paint bottles, and sometimes will hand paint small flowers or other things. It can be a pain, but I've recently found that Krylon Fusion paint seems to do real well.
Bob