Slate / Stone Engraves fading

#1

Hey Y’all,

I had great success engraving some off-cuts of large Black Limestone flags a while back. I was oiling them up with a beeswax / mineral oil mix first and then letting them sit for a while before engraving. Here’s a pic of one I just did (obvs the left one) and one I did a while back. The older one has faded in a bunch of places which is really disappointing. I’m not sure if excess oil has spread to those ares or what. I’ve given the older ones a scrub with soap and water but they’ve not come back to what they were at engrave. Any ideas? Do we think this is a natural ageing of the material / engrave or could I prevent it?

Here’s one of the faded piece not long after engrave.
before

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#2

Would be harder with Slate but painting the design and wiping off the outside would keep the design fresh. It may look good for being clean and dry while the rest is full of wax but nothing stays clean and dry forever,

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#3

I’m not sure what you mean tbh. If you’re thinking of painting into the engrave then I don’t think that’ll work since the engrave doesn’t actually seem to remove any of the surface material. I could try spray paint and see if the oil in the surface prevents it binding to anything not engraved but I don’t hold out much hope tbh.

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#4

That would be my thought. and that using very high power and high LPI would at least spall or degrade the the material enough to leave a real mark,

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#5

That’s interesting…I ran my initial engraves on slate without oiling first, and they haven’t faded…but they were never quite as sharp as the ones that had been oiled first. It might just be what ultimately happens to engraved slate. :thinking:

I wonder if a thin coating of varnish first would have better staying power. What we’re seeing with the oiling might be a difference in how the light reflects off the slate…varnish should accomplish that as well, without evaporating. (Might yellow a little with time.)

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#6

Agreed on the varnish @Jules as it’ll dry / set first. I was going for something food safe so you could serve cheese on these. I don’t even really know if they need sealing but I also agree that the engraves loom sharper if they’re oiled first.

I’m assuming that the oil is getting in to the engraved sections and darkening the surface there. Not sure how I can stop it really :frowning:

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#7

I used Tung Oil on slate and let it cure for a few days. Same effect, but no issue with Oil seeping into the design.

image https://discourse-cdn-sjc1.com/business5/uploads/glowforge/optimized/3X/9/f/9fdbd00fe0311786682d3bd386be5dc40a794a75_1_666x500.JPG

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#8

15 mins isn’t a long time for it to cure so you could try waiting longer? I ramped the power this time to see if that makes any difference. Interesting that the effect is the same on slate. I might start scrubbing the excess oil off before I laser them and see what difference that makes. I’m just reluctant to see them if this is what happens over time.

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#9

It needs to cure overnight. 15 mins will show the same effect as mineral oil. I think I mentioned that in a later post. I’ll edit it to show that.

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#10

Nice sign & great technique for a sign–but tung oil is not best option for food safe…

But ultimately for a cheese plate or other serving tray, it will be getting washed, and no matter what oil works initially, it will eventually be worn & washed off… Maybe the best option for food related items are designs that look best with just the texture & depth difference w/ the etching, and those won’t be significantly changed over time vs. those that rely on color difference…

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#11

Good point. I’m using mine as a coaster.

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#12

I did some slate coasters like a year and a half ago for my boss’ boss’ boss. I was looking at them the other day and they still look great. I never used any sort of oil on them at all.

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#13

I actually went back through my notes on the one which has faded was actually an early test with Boiled Linseed Oil which, like Tung oil should set if left to cure. This one cured for a while before I got up the courage to engrave such a large piece.

@bansai8creations - there’s no sign of the design wearing off or washing off, it’s just that the original brightness of the engrave disappears as the oil colours it back in. But I agree, maybe this isn’t the best use for the material which is a real shame.

@Tom_A hmm I was told that slate needed sealing before being used but perhaps that was just someone making it up. I imagine it helps stop it accruing stains but maybe it’s not essential after all!

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#14

I have no idea. Being a fool who rushes in, I didn’t know any better and didn’t even think to ask the question. It was my first slate attempt. After reading about people using oil I tried some and didn’t see any difference at all in the effect. (Of course initially the wetness of the oil make it look like more of a contrast but once it dries a bit I can’t tell the difference.)

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#15

This is why I went with Tung Oil, for a more lasting effect (contrast). Probably not food safe. Some slate is more gray and some is closer to black, so maybe it depends on what color your pieces show and target usage to decide whether treating it is helpful.

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#16

Pure, unrefined tung oil from the seed is food safe, even for those with nut allergies. It looks great on the slate!

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#17

Thanks for the info!

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