mdsparks

I am in the process of finishing a pair of mahogany dressing tables. I am using shellac for the finish. For all but the top surface I have finished to a nice sheen by sanding and buffing with 0000 steel wool. Then used a quality paste wax for the final finish. This turned out nice. The top surface however is a different story. For the top surface I have decided on a gloss finish since it presents the beauty of the wood so much better. Therefore, no sanding or buffing with steel wool on the final coat. After several days the surface is still soft. Soft enough that when I press my finger to the surface it leaves an ever so slight impression. The shellac is new (Zinsser shellac with a born on date of 10/10/07) and the finishing area warm and dry. I have applied the shellac in several 1 lb and 2 lb coats with sanding and steel wool buffing between coats. I’m afraid that since it is a dressing table that objects left on top will leave impressions in the shellac and ruin the finish. Is it normal for shellac to be this soft? If not does anyone have any ideas what I am doing wrong?

Thanks in advance
Mike

BlockHead

That defianately doesn't sound right at all, it should dry to a hard finish within a couple of hours at most. Are you using the same batch of shellac you used on the sides? Also, the same brush, container, etc... I'm wondering if the shellac may have gotten contaminated somehow, maybe from the wax.

Wait and see what others have to say first, but I think I would break out the denatured alcohol and remove it from the top and start over with a new can of shellac, new brush and clean container. But like I said, wait and see what others have to say. I'm just a newbie.

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Youngman

Did you reduce it or cut it with something other the alcohol?
http://en.wikipedia.org/wiki/Esterification this is a what happens if the shellac sits too long. It does not dry. It is old..

mdsparks

I cut it with denatured alcohol. Today I noticed the portions other than the top are also displaying evidence of slight finger print impressions left when grasping the piece to move it. They can't be wiped clean. At first I thiought they may just be prints left by skin oils, but they are actually impressions of my finger prints.

Thanks for the reference to Wikipedia. I read the Wikipedia link earlier and learned of the problems that accompany old shellac. The shellac is brand new. Maybe the Zinsser brand is not a quality brand, but I have used their other products with no problem in the past.

Just can't figure this one out. Never used shellac before so I'm not sure what degree of hardness to expect. But, I would certainly think that the pressure applyed by a typical grasp should not leave impressions in the shellac.

Mike

Rob

Any chance you used linseed oil under the shellac that wasn't cured yet?
Just a thought.

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clampman

That sounds exactly like old shellac - or possibly the alcohol you cut it with. Alcohol will absorb water very quickly.

The same thing happened to me years ago, and I have used nothing since but dried shellac flakes mixed with sherwin williams alcohol. I use it as a 1 lb. wash coat under conversion varnish, and never have had a problem since. The solvent alcohol at SW specifically mentions using it for dissolving shellac flakes. It was cheaper than at home depot when buying it from the industrial coatings store.

You should be able to sand it within a half hour if the air is warm and dry.

Rob

You know...it wouldn't be that hard to buy a quart of fresh shellac...empty the contents and pour some old stuff you've had sitting around for 5 years in the new can and return it unused. If you were careful and didn't make a mess, no one would know the difference until using it.
Just another random thought.

I also use flakes. I heat mine up in a double boiler affair on top of an old glue pot heater. I can get a batch dissolved in an hour or so.

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aclose

ouch. and what if you were the next guy to buy that bad shellac?

Rob

That's what I'm saying...that you'd get screwed. I've heard of people putting used tools back in new packages and returning them to the big box stores, so I can see someone pulling this stunt also to save $5.

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mdsparks

No. But I did use a gel stain over the second coat to help blend the color of the wood more evenly. The excess gel stain was removed allowed to dry overnight for at least 12 hours before proceeding with applying additional coats of shellac.

Do you think the gel stain could be the problem? I've read articles that recommend using dewaxed shellac as a sealer then gel stain to even color another coat of dewaxed shellac to seal the gel stain and then polyurethane as a top coat. Only difference here is the shellac is not dewaxed and there was no top coat of polyurethane.

mdsparks

I purchased some dewaxed flakes a few months back but never used them. Since I did not need dewaxed shellac I thought I would save them for future use and buy the Zinsser shellac for this project.

I have never mixed up my own shellac flakes before can you give me a step by step procedure and specifics on the solvent?

Thanks
Mike

Rob

Here's an article by Jeff Jewitt
http://www.taunton.com/finewoodworki....aspx?id=28833

Like I said, I use an old glue pot hot plate to help dissolve mine. I put an old pot with about 2" of water on the hot plate. I put the shellac flakes and the appropriate amount of denatured alcohol in a quart mason jar and just set it in the hot (not boiling) water and stir every 10 minutes or so with a paint stick.
The more pulverized the flakes are, the faster it will dissolve.
You can put some flakes in an old, folded dish cloth and roll it with a rolling pin. This will get pretty good results. I have an old electric coffee grinder that I use once in a while but with the heat, the stuff dissolves pretty fast out of the package.
Pretty simple really and you will have a good fresh product to use.

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Rob

Personally, I don't think that was enough time. I probably would have waited at least a full day...maybe longer.
I just found this out and will share...
I have a can of commercial shellac in my trailer. I read the can the other day and noticed that it shouldn't be used under polyurethane. I have never heard this before. Anyone else?

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mdsparks

I have read several places where the key to using shellac under poly is that it must be dewaxed shellac. The wax in shellac that has not been dewaxed does not alllow the poly to adhere properly.

clampman

Good call, Rob. I never suspected there was any stain involved from the post.

I don't like oil stain because even using this PITA technique http://www.miterclamp.com/radius/pag...tm#stainingtop

you still have to wait at least 3 or 4 days for the stain to dry before top coating. With porus woods like mahogany and oak, you might have to wait a week or more. And you can't use grain filler, then stain with oil or it will lift out the filler. So if you don't want to use a waterbased stain, you will have to stain then fill.

For the kind of look I think you are after, I don't think you will be happy unless you fill the grain. Shellac builds very slowly.

Michael Dresdner has a good book on finishing that is hilarious. I don't think his original one is still publlished, but I see he has an updated edition that Im sure you would enjoy and learn a great deal from.

Good luck.

Regards,
Jimc

mdsparks

I received a reply today from Zinsser regarding my results. They suggested that I may be experiencing sovent entrapment due to the number of coats. I tend to agree with this forum's earlier opinions regarding the middle coat of gel stain contributing to the problem. However, their solution is an easy one compared to removing the entire finish and starting over. So I think I'll try it first and post the results here.

Zinsser suggested that if it was due to solvent entrapment that I should try lightly wiping the surface with denatured alcohol and let dry. Then apply a few coats of paste wax for additional hardness and protection.

I'm going to try this in the near future and will post the results for anyone interested.

Mike

jerry

Shellac is an evaporative finish and I suspect that the gel stain didn't allow the shellac to cure. Suggesting that wax will harden and protect is a very bad joke, it offers little protection against anything. There is a lot of mis-information regarding shellac and polyurethane varnish. Shellac is a very hard finish that is naturally glossy. Polyurethane varnish has adhesion problems; one of which is sticking to shellac that is natural (contains wax) it also has trouble sticking to its self(thats why you have to sand between coats). I also don't think it is a good idea to use steel wool between coats of finish, if any trace isn't removed the water vapor moving through any finish will cause the steel to rust. My best guess is you will have to remove the finish and start again or live with what you have.

Good Luck
Jerry