Engraving glass with a 4.2 Watt blue diode laser

I have seen and heard of several different techniques for engraving glass with a low power blue diode laser. I recently came across the idea that one could use black cardstock instead of paint or a solution of titanium dioxide. I had a couple of pieces of 100 x 100 x 4mm glass tiles that could be used as drinks coasters. The glass is very clear and flat with all of the edges being rounded.

I found a simple pattern of a tribal bird that would show how well darker areas would fill in with the frosted effect i had wanted to achieve. Between the glass and the MDF I placed a layer of 220gsm card that was described as ‘very black’ by the vendor. I taped the glass tile to the MDF support and clamped the MDF so that the tile could not move.

My settings for my 4.2W blue diode J-Tech laser were 80% power (not continuous) and 400 mm per minute traversal speed. My laser is set to focus through a high resolution lens at 3.175mm (1/8"). Overall, the result is not too bad. The depth may be an issue because the 4mm thickness of the glass tile meant (in theory that my laser was only focussed to 3/4 of the thickness.

The end result had surprised me. The card had an amount of soot on it from the burn, perhaps to a depth of 0.1mm. The glass tile was engraved well but it was very smooth to touch (the micro-fractures could not be felt very easily so the lasered areas were only very slightly rough to touch. This may have been a fault in depth specification again.

The tile was cleaned with acetone before the engraving process and afterwards it was cleaned with soap and water to remove the sooty residue. The lasered side was washed in acetone before the final process of applying black paint. After it has dried properly, I will remove the paint from the glass and hopefully leave the lasered area completely black. It did not feel that it was well etched and there was no obvious deep etched area where the laser had been.

This is the design that I had wished to etch.

This was the setup on my CNC machine

This is the remaining soot on the card from the side that touched the glass

The finished glass tile burn (resting against the MDF support)

Finished glass tile resting against wooden bench

Total time for burn just over 35minutes. Advantages: Smooth outlines and very smooth on the lasered side. No painting or complicated coating processes required, just a piece of black card behind the glass. Disadvantages: Possibly difficult to obtain a really deep etch as one is lasering the tile with a beam that penetrates the whole tile. To obtain a more clear image then possibly the Norton method is applicable for that purpose.

Links to lasering through the glass using black card. Highly technical discussion of Norton method.

The black card method I copied from this gentleman at MellowPine Lasers

The Titanium Dioxide White Paint Method is explained beautifully by Russ at SarbarMultimedia. The explanation of black etching ceramics is highly technical and very informative. The link is to part one and part two is also available.

If any LightBurn user can make suggestions about how I may vary the depth of my burn and create a deeper etching as well as a darker etching using black card, I would be happy to hear if anyone has managed to improve the results.

You may find something interesting in a fairly lengthy thread here on the LB forum where I use a little 2.3W Banggood diode laser and the NWT method on ceramic tiles… and then extend it to transparent window glass. Along the way I “discovered” a “no-paint” technique using cereal-box cardboard (chipboard?) as a backing… with comparable results to using black paint (tempera or spray). I also demo a method to create two-step “two-color/tone” glass engravings, differing only in the paint used for each step…

Check it out…

– David

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The Laser Everything Video is excellent in details of how to achieve the best possible dpi/lpi for any laser and/or material. Might help you get a better image if you could dial in the dpi/lpi…

Understand it’s the heat from the black paper that is causing the glass to shatter. Usually referred to as the indirect method of engraving.

To get more shattered glass you need to put more heat on it. If your laser is burning the black, it will probably go through and heat up what’s behind that…

That does a couple of things, lowers the possible resolution because the size of the heat area increases. It changes the speed/power values as now you’re lasing a different material wanting the same effect… The paper will react differently than the mdf…

Since you are already a half mm out of focus, this will just aggravate the resolution and heat issues…

Go to ACE or something and pick up some thin glass, lase, properly focused through he thin piece → black paper → heating the glass tile. It will be on the other side, so make the proper adjustments.

You can at least get proper focus… and see if that helps your depth. The simple truth is it will be difficult to get much depth out of this setup… doesn’t mean it isn’t possible…

The ntm and TiO2 have numerous links on this topic…

I wish I could do what @Bulldog does… :sob: this kind of quality has eluded me so far…

This is on a co2, I belive.

This is his fiber …

Good luck


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Thank you very much! I will check it out.

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Another comprehensive answer. Thank you very much. I probably have more than enough to experiment with now.

Further testing gave me better results. After reading a lot more information, I had another attempt. This was an improvement with better fracturing so that it could be felt as a roughened surface. I used the black paper and slowed the traversal speed from 400mm/min to 100mm/min and I left the power at 80% on my 4.2W J-Tech diode laser. I now have cleaner edges and a darker image on glass.

Bird one was at 400mm/min

Bird two was at 100mm/min

In my view the additional time penalty (about 1 hour and fifteen minutes extra) is more than justified by the better result. Additional information is that I set my laser to its normal 3.175mm focus point but then subtracted an extra 1mm from the Z height so that the laser beam was now focussed at the bottom edge of the 4mm thick glass. Thanks to @dkj4linux and @jkwilborn for the links and the advice. I also was pleased to have the support of MDF underneath this because the burn penetrated the paper this time and scorched the MDF.

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