Using the formula 3 parts water & 1 part School Glue:
Cobalt Oxide yields a dark blue on glass and tile - much more pleasing than black from TiO2
Black Copper Oxide (CuO) yields a dark metallic copper
Power settings vary a bit for tile and the type of glass. The oxides can be mixed to get different colors, but I haven’t tried it. I’ve tried Chromium Oxide, but the result was a metallic grayish blue. I haven’t tried mixing the Chromium Oxide to see what I get, yet
Using a LaserPecker 4 (10W), tile is 54mm/sec, 39% power
Glass is 50% power, 45mm/sec to 60% power, 31mm/sec
A VERY thin coat of Sax Ivy Green glaze yields a dark green coat on tile and glass
A VERY thin coat of Sax Cranberry Red glaze yields a dark brownish red on tile and glass
A VERY thin coat of Sax Old Navy glaze yields a light blue on tile and glass.
On tile, the glaze is very low temperature, so the power is 6%, and speed 54mm/sec
The Picture:
Cranberry Red Cat, CO Rose, Ivy Green Leaves, TiO2 stems, C3oO4 text, Old Navy Cat, Co3O4 Salt Label on Glass
Yes. I have the file broken up into rose petals, stem, leaves, and text, each on a different layer. I engrave the CuO first, first, wash it off, then the stem, wash it off, then the leaves, wash it off, then the text. The tile hasto be in a fixture so it can be removed, washed, coated, then put back. I do everything with a brush. The rose petals I do twice to get rid of brush marks.
The oxides are from the Pottery Supply House - https://psh.ca/
I bought the smallest amount 100g. Unlike TiO2, the oxides settle very fast so I only mix up a small batch at a time and the mixture must be stirred rather vigiously before use.
I apply the oxides with a soft bristle brush and the glazes with a foam brush. I’v tried thinning the glazes but what seems to work best is to apply it with a foam brush, then wipe most of it off with a soft cloth on tile. A really thin coat works surprisingly well. It is rather tricky to get right. To thick, and it doesn’t bond with the tile. To much power, and it burns the binder. The glaze on tile is quite low temperature. With glass, I put it on with a foam brush, and a much higher power - the power used to engrave glass with tempera paint.
Looking good. I bought a bunch of powdered glazes, metal oxides and strontium carbonate two years ago to try this very idea but I’ve yet to get around to it!
Yes. Each different color is a separate layer, and each layer is engraved separately. The tile has to be in a fixture so that you can remove it, wash it, and then put it back in EXACTLY the same place before engraving the next color. The good thing is that when applying the oxides and glazes, you don’t have to “stay between the lines” - you can just smear it over the area you want to engrave and any outside that engrave layer just washes off. To avoid wasting to much coating material, I do a preview of a particular layer, mark the boundary with a felt tip pen, and then just coat that area with a bit outside the marks.
It took me over a month and a gazillion tiles to get a working technique. There are a lot of glazes and oxides I haven’t tried yet. I have yet to get a bright red or bright green. I used to by tiles from Amazon at about $20.00 for 12, but the same tiles can be bought from Home Depot for a bit over $20.00 for a box of 100 so you can try lots of things without going broke.
The temperature at the focal point of a laser engraver is exceedingly high. The glaze on tiles melts at a relatively low temperature and I have found that a bit to high a power burns the binder in the glaze, which appears to be organic, and makes the color brown, and a still higher power vaporizes the glaze. Glazes are designed for a specific temperature for a long time, and the laser, even at low power, is a high temperature for a short time. Perhaps defocusing the beam at a higher power and moving very slowly would work better, but I haven’t tried this approach.
Glass appears to be a bit different and a higher power appears to be required. Although with glass, the glazes I’ve tried result in a more transparent (but frosty) color, whereas the oxides result in a shiny opaque color. I really like the cobalt oxide blue on glass on tiles.
Do you mind showing us a photo of how your jig is setup?
I use them a lot on mine but they are rather loose as is because of the material variance. I can produce a locked down jig … just curious how yours is setup and work…
Nothing really to show and I don’t have it setup now to take a picture. The LP4 has a base plate with a pattern of threaded holes. A right angle piece is screwed into the plate to capture the bottom right corner of the tile, and another to capture the top right corner. You just slide the tile in, and it is in the exact same position each time. If this isn’t clear, message me again and I’ll set it up and take a picture - right now, I’m set up to engrave shot glasses with cobalt oxide - they come out really nice.
Pretty much, except not quite the same because the heat is so brief and generally to high. Can’t get the really deep colors - so far, all of the glazes I’ve tried come out pastel. The only deep, dark colors I can get, so far, come from the oxides alone. Glazes are a mixture of stuff, with one major component being a ceramic to generate the coating. If I could find out and buy the compounds just used to color the glaze, likely I could get deep dark colors - the oxides are a component in glazes, and they work great by themselves.
If it hasn’t already been said, be careful with chromium - it tends to be quite toxic & many of its compounds are carcinogenic. Think Erin Brokovich (hexavalent chromium). While I’ve been told chrome is safe-ish in a kiln scenarios, I don’t know if that generalizes to laser exposure…
That said, thank you for sharing your experimentation!
Cadmium is far worse. I bought some cadmium to try and get a bright red - after I read the safety data sheet, I sent it back. Copper and Cobalt are not to bad, but still you don’t want to breathe the fumes. With laser cutting anything, the fumes need to be exhausted outside.
