How cool! Thermally fused. Essentially an enamel, a crude glass. From the texture I see surface tension of the fluid dominating and drawing into beads that fuse into one another.
In enameling, a clean surface is required for the glass to ‘wet’ the surface. Under heat of the torch or kiln, when the glass sits on the metal like a bead of water that spreads out, the temperature is right.
With the stone, we see these areas that don’t ‘wet’ because of impurities and off-gassing. Too bad we can’t achieve A smooth enameled surface (note to self, let’s try a flux…).
Right! I knew you’d like that. It looks to be very color dependent. I turned the tile over and did another test. This time all three runs were at a pace 1/2 of 500 with the other numbers we discussed.
The first pic was the second run where it turned silverish. By the third run (2nd pic) the black was much smoother that the first test and very glass-like. It’s interesting to see that it really hasn’t flowed into other areas. The laser burns much brighter when it hits the areas that turn black and it engraves much deeper too.
Just so I can keep notes of what I’m doing, if it’s too much heat/too slow , it doesn’t fuse, just stays the same silvery color. Sped it back up a little bit and it fused again
I also noted that the black slate (clay origin I presume) didn’t spark like the colored slate did. The colored being softer than the black in my interpretation. Interesting how the different areas react. A reflection of the mineral composition I expect.
Such an interesting exploration of slate. Thanks for sharing that!
Kinda fun, isn’t it.
I’m doing another pass on the original test of the round graphic to see if I can get it to melt smoother. (Yay for great alignment that allowed me to do it!) I realize now that they silver color and the sparking is coming from the laser going back over the slag produced in the first pass. I’m going to see if I can find some slate tiles at home depot tomorrow and play some more. We need to figure out what the deepest red mineral in the slate is as that’s what’s producing the black slag. Maybe I’ll go post a pic of the tile over in my rock group to see what they say. I’ll let you know if I learn anything.
I can’t see the sides well but if what you have is a high Iron fine grain sandstone, it would not be surprising if you were able to melt it. I was proposing something in that direction a while back so it is interesting to see just how deep you could melt it. The high silica should make the glass “wetter” while clays produce a much less mobile melt.
They were one of the first things my daughter and I tried - her mom has a PhD in Geology, so we thought a “fossil” in obsidian would be a good joke. This was in the first few weeks of having the machine, and there were lots of things to try, so we lost enthusiasm before we got a good result. Sometime I’ll have to try again.
Aww geeze, I can’t remember. I found the project on the home screen and it listed the setting last used as full power (on a basic) and a speed of 300. I did multiple passes though so not sure if it’s the right one. It’ll get you starting point though.
Hey everyone, I’m looking into engraving tile pieces. I noticed this write up, very nicely done! Question: I’ve seen some videos where people have some slight sparks coming out when they’re doing tile. Is that bad, and bad with any type of material? They don’t look like big sparks, just tiny and bright. Thanks!
FWIW, this stone in this post has a pretty dramatic spark, but like Eflyguy said, it’s really no issue. Just use common sense and watch for any real flames. (Which would be really weird with tile lol.)