Engraving ceramic / stoneware plates

hi all. i recently seen on glowforge instagram a ceramic / stoneware plate being engraved. i was wondering if any and all ceramic / stoneware is laser safe to engrave or if it is only certain types.

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There are certain types of stoneware and ceramics that can release toxic compounds once the glaze is broken and some glazes have toxic compounds in the glaze. These are usually inert after firing, but not always, and once they are powdered by the laser you don’t want to breathe them. If the material is advertised as food safe you should be fine, but if not you will want to make sure you aren’t breathing the result of the engraving in large quantities and wash the piece after engraving and handling. Most often the compound is lead, but cadmium and other minerals are used for color and may be toxic when powdered.

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DO NOT DO IT! I know the exact post you are referencing. Glowforge is not able to handle the filtering needed to not cause server damage or killing of animals that would be in the home for anyone that is generalizing ceramic and stoneware.

If you are very familiar with these materials then it is your own risk. However, if this is a material you are just trying because you saw it on instagram (where GF IG refuses to post the material and so you are having to guess what it was…) I would not recommend it.

I truly applauded you for posting on the forums about it though. You are not in the wrong, that was a very wreckless post on their IG team.

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Yikes. Is this loads different than engraving ceramic tiles from Lowe’s or whatever?

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From my understanding, a driving factor is the use case behind its development. Dinner where is usually made to look pretty and withhold heat changes more common in a kitchen. This causes certain coatings and materials to be used.

Ceramic tile is usually design for more of a look effect then a functional effect. So it does not have to be limited/bounded so much.

Basically there is a set of materials and coatings to pick from. Manufactures picked what is needed for the specific use of the item. So some uses will dictate a material that is not as laser friendly.

Hopefully that explanation is not a horridly failed attempt. Lol. It’s one of those things that makes sense in my head but I don’t know how to translate it to text

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Gotcha. Yes that explains a lot. Thanks for taking the time to reply. My knowledge of ceramics ends at enamels.

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I have worked with a lot of stoneware and it fires at really high temperatures, much higher than almost any tiles, I cannot think of any fired glaze that would be a problem. That said exactly what the material was is a different problem.

Even salt glazing that could be horrid would not be a problem if all the chlorine was driven out as it would be at stoneware temperatures.

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Being an Engineer, I went a did some research…

Glazes are usually mostly Silica with different metal oxides mixed in for color/texture. The laser doesn’t burn the glaze away, it “ablates” it, chips it away in a way (the metal oxides embedded within are already in a “burned” state because they’re oxides so they don’t burn either). Localized heating from the laser fractures the surface of the ceramic and turns it in to particulate/dust. Some of it might re-melt. But none of it combusts, so ceramics don’t produce noxious combustion byproducts. And there are no volatiles that “cook off”.

Glazes do sometimes contain heavy metals like Lead, and breathing in that dust probably wouldn’t be too good for you in the long run (though even if the glaze is metal-free, breathing in the dust probably isn’t so good in the long run), but the quantities exhausted during a typical engrave are unlikely to even move the needle on airborne particulates more than a few feet away from the exhaust. No greater a risk, arguably, than lasing Acrylic or other plastics. Or driving down the highway behind a diesel truck.

If you’re exhausting outside or through a filter, I think you’d be fine with any ceramic. Maybe with one exception - really old ceramics. They’re more likely to contain stuff that’s bad, like Uranium, you probably don’t want to be blowing out your window even in small amounts.

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Lead is used in ceramic colors as there are a lot of ways to get bright colors, but at stoneware temperatures most colors will evaporate off before reaching those temperatures and this is particularly true of lead. Even high silica glazes will run like water.
This is why Stoneware is primarily various shades of brown with only Iron (rust red) and Cobalt (very blue) being the only colors to make it to those temps. As Iron is everywhere the only way to avoid its brown colorant is to find a clay body with no iron (this is called porcelain)

Why volcanoes are different...

I have thought it weird for some time that for volcanoes it was high silica that exploded and high alumina lavas that were runny, which is the opposite of ceramics. As best I can tell, under high pressures and temperatures found at depth water is far more able to dissolve water into it, than when there is alumina.

As the volcano nears being able the erupt the lower pressures allows the water to come out of solution and so cooling the magma and increasing the pressures dramatically, causing explosions.

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By all I have learned uranium makes a yellow color in glass and the percent volume is so small (a maximum of 10% by weight of the silica oxide and the least radioactive) I would be surprised if you could measure it with a Geiger counter. However in Stoneware, while it might not boil out there would be no reason to use it as the yellow would be lost in the iron colorant bleeding up from the claybody.