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Discussion Starter · #1 ·
I have been making a set of coasters to go along with an oval cheese board. The coasters are the same design except they’re round and I used the opposite combination of wood for the coasters. They are made from Maple and Padauk and are 4” round X ¼” thick. I will attach self-adhesive cork on the back once they are finished. My problem is with the finish. I usually find finishing the most challenging part of my projects.

A brief background; my house is on the market and I’m trying use up what I have on hand before the move. This was all good wood but I was limited in my choices.

I decided to finish the coasters by first giving them a couple of coats of natural Danish Oil. I then waited 3 days for the Danish Oil to set up then used a rattle can of Minwax Gloss Spar Urethane. The final coat was going to a satin Polyurethane. My problem is that, after a week, the Urethane over the Padauk strips is still tacky. It’s dry on the Maple. I may have not let the Danish Oil dry long enough, I may have sprayed too heavy a coat onto the Coaters or the Urethane may have been too old. I don’t know if rattle cans go bad or not.

Knowing what went wrong would be interesting information, so I don’t repeat the error in the future, however, the important question is: “What do I do now?” Starting over is not an option. I’m out of the Padauk. Should I try to rub off the finish with Mineral Spirits, should I sand it down to take of the Urethane, or is there some tried and true method of getting the Urethane to harden? At this point I’m stuck and would really appreciate any suggestion as to how to save this project. It’s being made as a gift and we’re going to see the recipients in about 2 weeks.
 

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I know a lot of guys get away with all sorts of strange combinations as attested to on the Forums, but ever since Polyurethane came out (in the late 50's?). the generally accepted wisdom was that applying poly over any other finish was an invitation to disaster. I stuck to that policy and I've never had a problem. "Finish" of course doesn't mean you can't use an appropriate stain...but not with an oil base that needs to cure.
Just my opinion...
Personally, I'd strip it and start the finishing over.

ps in a discussion up here last week, the topic of 'Danish Oil' came up. It turns out there is no one formula for it. Manufacturers use whatever they deem appropriate for ingredients, although Tung oil sees to be most popular(?). If that's the case then you might get away with using one brand + poly, but not necessarily another.
 

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It just occurred to me that if there's any wax in the 'Danish Oil' stain, Polyurethane won't stick, or at least it won't cure.
 

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Given that the poly set on the maple parts, I think it's insufficient curing time for the oil. I guess it soaked into the two woods differently and that resulted in slower curing on the padauk. I know the Danish oils I use take a long time to cure, like a week before it feels hard when you tap it with a fingernail.

As Dan said I think you'll have to strip the poly. Not sure of the best way to do that. The cured poly on the maple would resist many solvents. Paint stripper would do it but sanding might be the best bet. Then re-oil and wait a bit longer before over-coating. There is a lot to be said for testing the finish on scraps first, especially if you're using a new combination or old stock.

I love the design of the coaster by the way, it looks great. Hope you manage to resolve the finishing difficulties in time, I'm sure the recipient will be very pleased with them.
 

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Use oil very sparingly, just enough to change or highlight the grain and then cover with un-waxed shellac as a sealer coat immediately. The oil will cure under the shellac, which dries very quickly, and poly will adhere to shellac without a problem and dry at it's normal pace.

Just remember the shellac must un-waxed.
 

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Discussion Starter · #6 ·
Thank you all for your suggestions. I'm sort of taking all of them. I used mineral spirits to wipe off the spots that were still tacky. After letting them dry and continue to harden overnight, I sanded with 150 then 220 grit sand paper and have given them 2 coats of Zinseer Sealcoat. Tomorrow I'll lightly sand the shellac and put the first of 2 coats of poly on them. After they dry I'll put the cork on the back and complete the stand using the same sequence of finishing. Due to other commitments, I probably won't get them completed until next week but, once done, I'll post some pictures.

Thank you again for your help. I've learned a valuable lesson from this and, to me, that's what woodworking is all about.
 

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Earworm

"Urethane won’t dry"


I've got My Boomerang Wont Come Back as an earworm now;
thanks a lot! :laugh2:
 

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Discussion Starter · #10 ·
"Urethane won’t dry"


I've got My Boomerang Wont Come Back as an earworm now;
thanks a lot! :laugh2:
Sorry, the coasters are the wrong shape to return when thrown. I was almost ready to check that out, too.
 

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Discussion Starter · #11 ·
Sorry it's taken me a while to update this post. I was out of town for a week due to a family emergency but that was taken care of and I was able to complete the coasters and their holder. The use of mineral oil to remove some of the tacky finish permitted the coaster to dry enough that I was able to sand them, put a coat of Zinseer Sealcoat on followed by two coats of poly. Once the coaster were dry I put 1/16" self adhesive cork on the bottom and trimmed it with a sharp Exacto knife, tilting the knife about 30 degrees to form a bevel on the cork. I then lightly sanded the edges of the cork with 220 grit sandpaper to smooth over the bottom edge and remove any hanging threads. With that completed I was able to stack them in the stand, cut that to height, round over the posts and finish the same way I finished the coasters.

Thanks again for your advice. I guess all's well that ends well except for the additional gray hairs I've acquired during the process.
 

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those are sweet...
now how do we teach Dan better manners???
 
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Dat you Leroy????
 

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Nice coaster, BTW, Barry.
 

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Discussion Starter · #20 ·
Thanks guys but, don't pick on Dan, he has the right idea, especially the "Wikipedia" definition. I may enclose it with the coasters when we give the gift to the couple i made it for. One caution, when you say something tongue in cheek, make sure you don't bite down.
 
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