polyurethane vs shellac
To use as a bar, I would suggest poly. More durable and water resistant.
The solvent for shellac is...
Alcohol!
Absolutely not appropriate for a bar top.
Go with multiple coats of polyurethane. Underlying coats should all be gloss, which you can go over with 0000 steel wool between coats, vacuum and recoat. Final coat is sheen of choice.
Why not all sheen and forget the steel wool? (BTW bronze wool doesn't rust and is common in marine applications.)
If it's a bar top, then there are specialty (low viscosity) epoxy coatings for those. You can buy them off of amazon for instance.
Epoxy doesn't smell and is inert when cured, but don't get it on your skin since you could develop a nasty allergy to it (wear disposable non-latex gloves during application and a respirator when sanding "green" epoxy). Make sure you mix the ratios exactly right (a digital scale is often recommended) so that it cures correctly.
Mahogany has very open pores, which means that the poly/epoxy/etc will penetrate deeply, but during that process the air gets displaced, causing bubbles. You would see that on a heavy coat. So instead, apply a light coat first (and perhaps squeegy it in even), let that completely cure, sand down any bubbles, then repeat and/or apply your top layer(s).
mrmaplewood said:
Why not all sheen and forget the steel wool? (BTW bronze wool doesn't rust and is common in marine applications.)
Better adhesion between coats and knocks down any embedded dust. Bronze wool sounds good.
Doesn't make sense, make a glossy finish, then go to a lot of work to knock the gloss off for a sheeny finish. I'd go for all sheen.
You are misunderstanding me. We are talking about multiple coats here. One does not put gloss over gloss without prep. It is a recipe for poor adhesion and flaking. The final coat determines the final sheen and it does not get the steel (or bronze) wool treatment.
If you don't believe me, read the can.
Exactly what I'm talking about. If you put on 6 layers of poly, why bother with gloss, then making it sheen for the next coat. And so on. Got it?
jimmurphy said:
You are misunderstanding me. We are talking about multiple coats here. One does not put gloss over gloss without prep. It is a recipe for poor adhesion and flaking. The final coat determines the final sheen and it does not get the steel (or bronze) wool treatment.
If you don't believe me, read the can.
mrmaplewood said:
Exactly what I'm talking about. If you put on 6 layers of poly, why bother with gloss, then making it sheen for the next coat. Got it?
Is this what they mean by "spar" varnish?
evandepol said:
If it's a bar top, then there are specialty (low viscosity) epoxy coatings for those. You can buy them off of amazon for instance.
Available at our local Home Depot
http://www.homedepot.com/p/Rust-Oleum-Parks-1-qt-Gloss-Super-Glaze-Finish-and-Preservative-241352/202056337
This is a good choice for a high traffic environment. However, I actually wouldn't personally use this for a home bar top unless you want that thick plastic coated look of the bar tops in real bars. They need to stand up to heavy use and never need refinishing.
As mentioned above, shellac is not an option for a bar because it is soluble in alcohol. "Danish oil", which is simply a mix of alkyd varnish and boiled linseed oil, will form a thin film that probably won't be protective enough for a bar top. Lacquer is out unless you have a spray booth.
I would simply use a few coats of a good quality oil based polyurethane. It's easy to apply, will protect well and not look like it was poured on like bar top epoxy finishes. Apply 3 or 4 coats with a natural bristle brush. Sand lightly between coats only to remove any dust that may have settled in the finish while it was drying.
mrmaplewood said:
Exactly what I'm talking about. If you put on 6 layers of poly, why bother with gloss, then making it sheen for the next coat. And so on. Got it?
High gloss poly is harder than semi-gloss, which is why it should be used for underlying coats. If you do not feel it is necessary to do any prep between coats, slightly roughing the surface and knocking down any imperfections in the already-applied finish, then we'll just have to disagree.
And Dave, 
DaveSchmidt said:
jimmurphy said:
You are misunderstanding me. We are talking about multiple coats here. One does not put gloss over gloss without prep. It is a recipe for poor adhesion and flaking. The final coat determines the final sheen and it does not get the steel (or bronze) wool treatment.
If you don't believe me, read the can.mrmaplewood said:
Exactly what I'm talking about. If you put on 6 layers of poly, why bother with gloss, then making it sheen for the next coat. Got it?
Is this what they mean by "spar" varnish?
Satin varnish is simply gloss varnish with flattening agents added. Jimmurphy is correct that all but the last coat should be gloss, because if you build up 3 or 4 coats of satin, it can make the finish appear muddy and you will lose a lot of the detail of the wood grain. I use 220 or 320 sandpaper on a block to flatten it and knock down any dust that may have gotten onto it between coats. If you want a satin look, use satin poly for the last coat, or simply rub out the last coat with #0000 steel wool.
BTW, adhesion between coats is not as big a deal as a lot of people think. Sanding is more for the smoothing and dust removal. Bob Flexner addresses the issue here: http://www.popularwoodworking.com/article/the_7_myths_of_polyurethane
What Rob_Sandow and JimMurphy said. I watched my Dad do a lot of wood finishing when I was a kid, and that is exactly how he did it. And he used to research the hell out of his projects to make sure he did it JUST right.
so, my husband went w/ shellac. he later was soeaking w/ someone who built their own kitchen table and used shellac as a finish and put in...FORTY COATS! their table has withstood years of use and spills, so clearly they're happy w/ their decision and it sounds beautiful. - just wondering...for those of you who are pro-shellac...how many coats would you recommend? thanks!
I would suggest a tung oil finish, such as Waterlox. At least it can be touched up without totally refinishing, like poly.
no, a tung oil finish. It's food safe and can be built up, any scratches can be buffed and re-coated without refinishing the entire top. I did research about wood countertops (and floors) and opted to use this in several applications.
There are other similar oil finishes with different manufacturers. Unlike poly it soaks into the grain of the wood to enhance it, not cover it up.
I think the op's husband already went with shellac. But tung would have been another option.
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we have a piece of mahogony that we need to cover/protect. we plan on using it for a bar we are making. would you use one of these or would you recommend danish oil or lacquer..or something else??? thanks!