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Rather than rely on the wood type to repel the weather, you may want to consider using Envirotex Lite on the bar top.
One good coat of Envirotex is equal to 50 coats of varnish.
I used it on my bar and every year I sand the top and add a new coat to make it smoother and thicker. You can even place coins or other memorabilia in the bar and permanently seal them into the thick layer.
Envirotex is a two part epoxy and is self leveling. It needs to me mixed well before use (read instructions). If you get any bubbles in it, you can remove them by using a propane torch while it is still wet. I had a hard time believing this, expecting it to burst into flames, but it’s just like water and completely non-flammable. Don’t use too much heat, otherwise it will boil. Just a quick pass with the torch will magically remove any bubbles.
Envirotex LITE is available at most hardware stores.