Polyurethane not drying after engraving

I did an engraving on maple wood. After, I put a coat of Min-wax Wipe-on Poly Polyurethane and let it set over night. All the finish dried except where the laser engraving which remains sticky.

Any ideas?

I have noticed a similar thing, even when I had a coat of finish before engraving then added another after. It was only the after engraving coat that had this problem. I put it down to the finish pooling in the engraving (it was over 1mm deep) and also the now chard grain soaking up more. Mine does dry eventually, but it like I have put on a very thick coat.



As David mentioned the char remaining in the grooves of the engraving don’t dry quickly as on a flat surface, mostly because it puddles in the groove and I imagine the sap present in the cut deters it also. I brush the engraving with a nylon cleaning brush. That removes almost all of the char. I assume you are applying the poly with a brush. Wipe the bristles across the edge of the container so you apply a very light coating of the poly. With spray application, spray very light coats several times allowing each coating to dry first. Fiddly I know but if it works why not do it?

The second coat dried within the engraving, but about 1/8” around the burn is no drying. Strange.

I do a lot of boxes, and this is just a small annoyance. The poly gets absorbed by the wood fibers, and thus, the top coat is very thin ( what is truly exposed to the air ). But where you engraved, the char blocks the poly from going down into the wood, and sort of acts like a sponge, thickening the poly, and changing the chemical qualities a bit… ( Mixes it with ash … ) so it takes longer. The same is true with Oil, which I use more than the poly as a first coat. But I generally put it aside and let it dry 72 hours before doing the next step. I just am careful I don’t overfill the engraved areas, so the recommendation someone gave of brushing away excess is spot on. Maybe different Poly formulas give different results… I never use wipe on poly. When I use poly, it is either spray or brush.

Thank for everyone’s reply and insight. I lightly sanded down the last coat and wiped it down with Mineral Spirits. No damage to the engraving. I hit it lightly with a heat gun and it seems to be dry. So, today I will give it a couple light coats of spray Poly and see how it goes. The drying of the engraving isn’t the big problem as much as the small area around the outside of the burn areas. After the first coat of wipe on poly, the finish had what I would call an outer glow of tacky poly outside the burn areas.

The top of my Great-Granddaughter keepsake box. First thin spray coat of poly. All looks good. Thanks for your help.

1 Like

Finally found someone with the same issue as me! I can’t figure out how to fix it. Im making drink coasters out of solid wood (all types ive tried have same issue) and the poly will dry fine on all of it except around where the engraving is. It just stays tacky even days after applying it. Tried all different brands of poly and tried water based and oil, all the same problem. I have people wanting to buy these things off me and I can’t get the last step done. Running out of ideas.

If you aren’t masking your coasters before engraving you have some sap from the wood remaining around the edges of same. I mask everything when cutting a design or text.
You can’t do anything about the units you have already coated but you can wash most of the grunge off with “Simple Green”. I sand after removing the mask to remove any light residue.

Hmm. Interesting thread. Last year I made a few small wooden earrings that my wife colored with pens and then i sprayed with polyurethane. Even after a month the edges were still a little tacky.
Obviously other folks are having the same experience.

I have sort of got over this problem by really brushing out the coats of varnish, being very careful to not put it on too thickly. Another thing I have been doing is to dip the brush in White spirit first then really squeeze out the excess in a rag. This thins the coats ever so slightly and maybe helping with the drying problem. Certainly if I start with a dry brush the drying problem is a little worse. I then bring the parts into the house to dry in a warm place rather than the workshop that isn’t heated unless I am in there.

We’ll crack it eventually!

1 Like

This topic was automatically closed 30 days after the last reply. New replies are no longer allowed.