Have we determined what clear coats are safe to laser?

I’d like to get in the habit of painting, and clear coating plywood for projects PRIOR to cutting it.
Is this acceptable? Do we know what kind of paint and clear is safe to laser?

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Acrylics are okay. (That’s the only one I know for sure.) :slightly_smiling_face:

Shellac for the finishes.

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Sounds great!

Oil finish looks to be okay and does great.

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One consideration to the sequence is the laser opens the wood to the elements where finishing after seals it against environmental conditions.

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I attempted the traditional wax/orange oil and it works BUT… you must let the wax dry and be buffed for MANY hour previous to cutting for well what should be obvious fire hazard reasons. HOWEVER if you are gonna tape over it … just don’t, unless your gonna wait like 5 days the glue from the tape seems to react to the residual orange oil or wax because it becomes a gooey mess when you remove the masking. Now if I want a “natural” finish I apply afters.

Shellac is the shiznit! I have used Bullseye in both spray and brush on now. Thanks again to @Dan for providing that tip.

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I agree. Shellac is a great hard clear gloss finish.

Does anyone know if clear polyurethane is laser safe when Baltic birch is coated with it prior to lasering?

Polyurethane does not contain any halogens. So as long as your glowforge is well ventilated you won’t be damaging your glowforge.

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I have engraved hundreds of very thickly coated clear polyurethane maple tap handles. No smell, little smoke. Not going to comment on the safety. The nice part is I don’t have to mask at all. The smoke wipes right off with a damp cloth.

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With respect to buildup on optical components, I wish there were some qualitative data on resin or junk associated with material being used and coating present. E.g., Dan mentioned that MDF would shorten the recommended cleaning time.
With Baltic birch coated with polyurethane, I notice a sticky brown substance on the masking. Also see this with MDF. Don’t remember seeing this when cutting acrylic.
My main worry is centered on damaging the Glowforge.