Varnish (poly is a high test form of varnish) can be problematic in it's
application and, for various reasons, not one of my favorite. However if one
takes one time with the stuff it is a good finish and one most newbie's
start off with.
First rule on deciding what finish to use is to decide how much protection
the piece needs. The second rule it to decide what "look" you want. Third
rule is to pick one that meets both parameters. Though that sometimes means
compromises. If maximum protection is desired, there is no particular look
in mind, and one isn't going to rub out the finish, Poly will fit the bill.
Being a beginner I'd have to assume spraying is not an option which leaves
out lacquer so, on one side of the protection scale and since you want a
hard/clear finish, you have shellac and, on the other, varnish. Max
protection is varnish (poly) though both oil based varnish and shellac are
both going to impart, to varying degrees, an amber tone to you work. Water
based varnish, though it won't look it in the can, will be perfectly clear.
Water based also dries faster allowing two coats a day vs. one for an oil
based finish. You can tell which is which by looking at the clean up
instructions on the can. Oil based products will call for paint
thinner/mineral oil and water based, of course, soap and water.
So, yes, poly will be a good finish for your table top.
As to where to get it where you are. Sorry, can't help there. Two notes on
brushes though. If it is an oil based you want a natural bristle brush or
one of those cheap sponge rubber applicators. If it is a water based finish
you will want a synthetic bristle brush.
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