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Fixing Flaws in a Shellac Finish

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Forum topic by knotscott posted 10-18-2019 07:47 PM 431 views 1 time favorited 13 replies Add to Favorites Watch
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knotscott

8343 posts in 3920 days


10-18-2019 07:47 PM

Hi gang – I need some advice for fixing some flaws in a stained ash table surface. While applying a base finish of Zinsser amber shellac, I managed to create some easy to spot ridges/runs, probably from fiddling with it too much. I plan to do a final finish with poly. I don’t have much experience with shellac, and was wrongly under the impression that adding another coat of shellac would interact with the first coat and level it….it didn’t, so now my flaws have an extra coat of shellac. My first thought was to sand it back a little to level it, then proceed, but rather than screw it up more, I’m asking our experts here for ideas to salvage the finish without having to sand it all the way back to wood. HELP PLEASE!!

Below is one example, but there are a few others.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....


13 replies so far

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Rich

5001 posts in 1134 days


#1 posted 10-18-2019 08:04 PM

A denibbing tool is handy to keep around for shellac and lacquer imperfections. Since you probably don’t have one handy, a card scraper used gently will shave it flush. If you want to play it really safe, remove the burr from the scraper. Make sure the edges are square and sharp, just don’t put the burr back on it. Go lightly, since all you want to do is level it.

View wildwoodbybrianjohns's profile

wildwoodbybrianjohns

474 posts in 92 days


#2 posted 10-18-2019 08:44 PM

Yep, you went back into a run that was already setting, quite possibly with a too-dry brush.

Since you dont intend on building up a shellac finish, then Rich´s advice is probably best. As he said, go real lightly!

-- Wildwood by Brian Johns: It is wiser to find out, than to suppose (S. Clemens)

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knotscott

8343 posts in 3920 days


#3 posted 10-18-2019 08:50 PM

Scraping was definitely a good start, followed by a little DNA on a cloth, followed by 200 grit sanding. I think the poly coats will be fine now. Thanks gang!

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

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Aj2

2536 posts in 2342 days


#4 posted 10-19-2019 12:38 AM

Have you used that one under poly before.
I’ve heard it doesn’t play well with a top coat too much wax. But I’ve also others say it’s not a problem.
I use shellac when I can. I buy flakes and buttons from the shellac shack. It dries much harder then the can stuff.

Good Luck on your project

-- Aj

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ruger

132 posts in 640 days


#5 posted 10-19-2019 01:25 AM

just rub it out with 0000 steel wool. it will rub right out with very little effort. I use shellac all the time.

View QuangFromCalgary's profile

QuangFromCalgary

42 posts in 3543 days


#6 posted 10-19-2019 04:23 AM

Just use 320 sand paper for this. Light sanding this area and then put new coat on. You may have to put more than one coat of shellac to level it.
I think Zinsser amber shellac is not a dewax shellac. You may have the problem in a long term. Poly wont stick to waxed shellac well.

View Lazyman's profile

Lazyman

4113 posts in 1932 days


#7 posted 10-19-2019 12:00 PM



Have you used that one under poly before.
I’ve heard it doesn’t play well with a top coat too much wax. But I’ve also others say it’s not a problem.
I use shellac when I can. I buy flakes and buttons from the shellac shack. It dries much harder then the can stuff.

Good Luck on your project

- Aj2

+1. Make sure that the shellac is dewaxed if you are going to put poly over it. If you used the Zinsser canned shellac, it is NOT dewaxed. Their Sealcoat IS dewaxed but your picture doesn’t look like a sealcoat. IMO, if you are going to put poly on it anyway, the shellac probably isn’t necessary.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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knotscott

8343 posts in 3920 days


#8 posted 10-19-2019 12:21 PM

The shellac is from a can of Zinsser amber, so it sounds like its not dewaxed. What can I do to reduce the risk of adhesion problems with the poly?

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

View OSU55's profile

OSU55

2448 posts in 2534 days


#9 posted 10-19-2019 01:09 PM

You would need to remove most of the shellac. Wiping it off with dna can do it without removing the stain depending on the stain solvent. As mentioned some claim it doesnt matter and Ive never tested waxed shellac under oil or wb poly. IMO you dont need to fully strip, just get 90-95% off, others may have a different opinion.

View ibewjon's profile

ibewjon

1040 posts in 3338 days


#10 posted 10-19-2019 06:01 PM

I would top it with a couple coats of the de waxed sealcoat shellac, then do the poly. That keeps the color of the regular shellac. And no stripping.

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knotscott

8343 posts in 3920 days


#11 posted 10-19-2019 06:47 PM

Update – In a nutshell things went from bad to worse, so I spent the day sanding back to bare wood, and starting fresh with the stain. I’m waiting for it to try so I can proceed with the poly, and skip the shellac.

What happened you ask? When I went out to the shop around 9 this morning, I found a rag on one of the table halves…picked it up and it revealed a section of dissolved shellac bare wood underneath I can’t for the life of me think of a reason i would have left that rag there….I know better! Truth be told, I had a minor medical procedure done under sedation yesterday, and was warned not to drive for 24 hours. I didn’t drive, but worked in the shop, and somewhere along the way left a rag damp with DNA on the table….tough start to the day for sure, but all is well now. No one to blame but me! Sometimes this hobby is a love/hate thing!

Thanks for all the tips, but ya can’t fix stupid!

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

View wildwoodbybrianjohns's profile

wildwoodbybrianjohns

474 posts in 92 days


#12 posted 10-19-2019 07:58 PM

Oooh, thats a stinker. Oh well, ya live, ya learn- that sedation is always fun, but comes at a price.

-- Wildwood by Brian Johns: It is wiser to find out, than to suppose (S. Clemens)

View Joe Lyddon's profile (online now)

Joe Lyddon

10790 posts in 4597 days


#13 posted 10-31-2019 06:15 AM

Scott… with shellac, once you start, you must NOT STOP and go back… just keep on going…
Wad up a piece of cloth into a small ball, dip it into shellac and Starting at one end, land the cloth on the end of the board, keep going to other end, taking off… Dip into more shellac to keep it going…
... land & take off again… quickly… non-stop…

After 1st coat has dried, usually just a few minutes, sand very lightly, wipe-down, then go over it again hitting the places that obviously need it… NON-STOP on to end of runway…

Subsequent coats will melt-into previous coats…

Always add more coats where needed WHEN IT HAS DRIED first, etc.

I almost popped in and said to just go over it denatured alcohol until things were even & corrected… Then, start over again as described above…

Shellac is really easy to work with… IF you follow the above procedure…

In the future, you can always sand lightly & clean… followed by adding more coats as above… will end up looking better than it was before because the new coats will blend into previous finish…

Poly, etc. will always have to be sanded a lot to refinish… no where near as nice as shellac works.

Sorry, I should have popped in back when… but, I thought that maybe their way just might work… Sorry it didn’t.

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: http://www.WoodworkStuff.net ... My Small Gallery: https://www.ncwoodworker.net/forums/index.php

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