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Forum topic by jockmike2 posted 10-11-2009 03:47 PM 1850 views 0 times favorited 20 replies Add to Favorites Watch
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jockmike2

10635 posts in 2937 days


10-11-2009 03:47 PM

Topic tags/keywords: question

I put about 5 coats of shellac on an outdoor bench not realizing the sun would make it blister. Could I now put several coats of Spar Varnish over that without making a mess of things. In other words after the varnish could I then set it outside without it blistering? Thanks, mike

-- (You just have to please the man in the Mirror) Mike from Michigan -


20 replies so far

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jockmike2

10635 posts in 2937 days


#1 posted 10-11-2009 04:34 PM

Yup noto, but I’ve already sanded it down and got the pits out.

-- (You just have to please the man in the Mirror) Mike from Michigan -

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Dick, & Barb Cain

8693 posts in 2990 days


#2 posted 10-11-2009 05:11 PM

What kind of wood is it. Maybe it’s sealed to good, & if the wood still has moisture in causing the

blisters. Maybe you should try an UV resistant oil finish.

-- -** You are never to old to set another goal or to dream a new dream ****************** Dick, & Barb Cain, Hibbing, MN. http://www.woodcarvingillustrated.com/gallery/member.php?uid=3627&protype=1

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Karson

34891 posts in 3091 days


#3 posted 10-11-2009 05:25 PM

It sounds to me that you are trying to put a coat of varnish on top of a defective (non holding) finish. I don’t think that it will work out.

But what do I know. Can you do the same thing on a wood sample and find out.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware karson_morrison@bigfoot.com †

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jockmike2

10635 posts in 2937 days


#4 posted 10-11-2009 05:40 PM

The wood should be dry. It’s a hunk of slab wood I got from the sawyer 2 winters ago. I’ts been in the garage for at least 2 years before I put the shellac on it. I didn’t put anything on under the shellac, just sanded it smooth. Then left it in the sun to dry. Next day it blistered all over where the sun hit it. I just finished cleaning the back down to the bare oak and re-sprayed it with spar varnish about 5 coats. Too labor intensive. I was hoping I could just put a couple coats of Spar on the seat and call it good. What do you think. I sanded the pits out of it but it still has shellac on it. So you are saying Shellac should not blister in the sun?

-- (You just have to please the man in the Mirror) Mike from Michigan -

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mski

412 posts in 2671 days


#5 posted 10-11-2009 05:49 PM

My 2 cents, is if Shellac is blistering you still have moisture in the wood.
So spar varnish will blister too, only a bigger headach to fix.
2 years air drying may not be enough for a thick slab of oak, I think they say a year an inch for air dry.

-- MARK IN BOB, So. CAL

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jockmike2

10635 posts in 2937 days


#6 posted 10-11-2009 05:55 PM

Wow, thanks for that tidbit. If only you had told me sooner. LOL. Thanks very much for the info. Yea it’s a pretty thick piece of oak. Well back to the stripping. So all that work on the back rest was for naught? Bummer.

-- (You just have to please the man in the Mirror) Mike from Michigan -

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jockmike2

10635 posts in 2937 days


#7 posted 10-11-2009 06:05 PM

Ya, that’s it. That’s the ticket. I’ll just wait a few months for it to dry. Then try it again. I love you noto. You make my life so much easier. LOL.

-- (You just have to please the man in the Mirror) Mike from Michigan -

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a1Jim

112335 posts in 2268 days


#8 posted 10-11-2009 06:24 PM

Hey Mike Shellac is one of the one finises that has the least resistant to water It could be as others have suggested that the wood is not dry or it was to moist. Shellac will redisolve with a spray of denatured alcohol or more coats of shellac. I would re coat with on of those and set it inside if you don’t have problems then it was the outside conditions if you do have problems it’s that the woods to wet. The great thing is that shellac will let anything bond to it so you can spar varnish after the moister problem is addressed

-- http://artisticwoodstudio.com Custom furniture

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a1Jim

112335 posts in 2268 days


#9 posted 10-11-2009 06:29 PM

One other option is that your shellac has gone bad it does not have a real long shelf life. You might apply some to a dry scrap of wood and see if it does the same thing.

-- http://artisticwoodstudio.com Custom furniture

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jockmike2

10635 posts in 2937 days


#10 posted 10-11-2009 06:34 PM

Thanks Jim, I really may have put coats of shellac on wet coats. I just can’t believe that wood was wet. It laid aside my woodstove all last winter. That should have sucked all the moisture out of it. But, then again. I did put alcohol on it and stripped some of it off, and sanded it down smooth. Maybe I’ll wait till spring and see what it does. Or set it out in the sun right now and see if it still blisters. So shellac, in itself, should not blister from being in the sun?

-- (You just have to please the man in the Mirror) Mike from Michigan -

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Tony

978 posts in 2721 days


#11 posted 10-11-2009 07:38 PM

Hi Mike.

I would get the bench back inside for the winter, as has been already stated that slab may not be dry enough. Can you post a picture of the bench so we can see the thickness of the lumber used in the bench and possibly the extent of the blistering.

Is the blistering all over the bench or just on the slab?
Is the blistering only where the sun has had direct contact with the bench, or is all over, including under the seat?

It is said, a year for each inch of wood for it to air dry – that is a very general rule of thumb – I would say that if the oak was cut in the spring, then you may have to allow 2+ years per inch (full of sap), even then, that will probably only dry to 15% or so, which is ideal for outdoor use – for fine furniture use you need about 6 to 8% and the only way to achieve that is to have the wood in a controlled environment with a RH of about 35 – 45% and a temperature of about 68° F (20°C) with this dry warm air moving across the face of the wood constantly.

Personally I would not use shellac on an outdoor project, not even as a sealing finish- it is not a finish that will withstand the elements or abuse that outdoor furniture will receive.

Just think – if you apply the varnish on top of the shellac, then the varnish is only bonding to the shellac, not the wood, so the slightest lifting of the shellac and the varnish comes away.

Ideally you want a deep penetrating sealer – if you decide to go with varnish, then you should apply one or two coats of varnish thinned with 40 – 50% mineral spirit (this will penetrate the wood very deeply, then you can start the process of apply the full strength varnish on top of the diluted varnish, this will cause a very strong, deep bond between the wood and the finish. In the end grain, especially the legs, where it comes into contact with the ground, I would soak these in the diluted varnish for at least an hour and leave the project for a week or two (depending upon conditions) to dry and slightly harden before continuing the process.

As for cleaning the shellac off – you have done most of the work, sanded and applied alcohol to clean the wood, but go over the whole project again, checking especially at the joints that the is NO sign of any shellac left ( not forgetting that Oak is an open grained wood, so the shellac may have gone deeper than you imagined) if there is this will be a week point in the finish.

I hope this helps you a Little in deciding

-- Tony - All things are possible, just some things are more difficult than others! - SKYPE: Heron2005 (http://www.poydatjatuolit.fi)

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jockmike2

10635 posts in 2937 days


#12 posted 10-11-2009 08:26 PM

It helps a great deal Tony in deciding what I’m going to do. I just stuck the seat portion out in the sun to see what would happen. I have that almost completely stripped of shellac. The back of the bench I have already stripped completely and started spraying with a mixture of BLO, mineral spirits and varnish. As I continued adding coats I just used spar varnish for the last two coats. After looking the bottom part over, I took them apart, I nearly have that stripped of shellac, so I’m going to go ahead and finish. Then start the same process as I did on the back. It’s about an inch and a quarter thick, with the legs being almost 1 3/4 inches. What do you think of the process I did on the back? Is that going to work or should I just let them be until spring. Thanks for the advice all and to you Tony.

-- (You just have to please the man in the Mirror) Mike from Michigan -

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GMman

3902 posts in 2388 days


#13 posted 10-13-2009 03:42 AM

Sorry Mike unable to help.

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mski

412 posts in 2671 days


#14 posted 10-14-2009 02:22 AM

Mike,
Been out of town but a late added note,
What seems dry and actually seems too dry could be very wet.
A SLAB (2+ inches) of wood will be so dry on the outside that it is cracking, one would think it’s ready, but in reality the center is no where near dry, and that moisture will go one way, out under your finish, that is why Anchor seal or the like is appiled to drying wood ,it lets the inside dry while keeping the outer from splitting.
Keeps the outer part of the wood from getting too dry while the center SLOWLY dries. Research the turning woods and they have alot of info on green wood curing.

-- MARK IN BOB, So. CAL

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jockmike2

10635 posts in 2937 days


#15 posted 10-14-2009 12:41 PM

Thanks Mark, yea I think I will wait till spring to finish it.

-- (You just have to please the man in the Mirror) Mike from Michigan -

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