A few months ago, I refinished an old Teak picnic table I picked up
for a bargain. The previous owners had put all sorts of finishing
agents on it, and it looked pretty splotchy and bad. So I got a
vibrating sander and took it down to the bare wood.
I know that teak weathers out to a nice silver patina, but I really
prefer that golden 'hardwood floor' look of varnished wood, so I got a
quart of marine varnish and did some internet research.
Most of the sites I found were about refinishing boat decks, and they
mentioned things like putting on 10 or 12 coats, and how even that
required refinishing every few years. That seemed excessive to me, so
I figured it had something to do with the rigors of salt water and
spray, and probably wouldn't affect my table on the back deck.
So I put one coat on the tabletop, which made a huge improvement (of
course), and then a second coat, which made a bit more of an
improvement. But the third coat barely made any change at all, so I
stopped after three coats.
For about six or eight weeks, it looked great and all the neighborhood
wives oohed and ahhed, but then little 'bare spots' started showing
up. Over time, they grew and increased until now when about 20% of the
table has exposed patches that are showing that silver teak patina
instead of the golden brown finish. So today I had to restrip the
table and start over.
My question: where does the varnish go? Why does something require
10-12 coats to last? I surmise that it might be one of these things:
a) varnish actually evaporates over time
b) the wood soaks up the varnish from below
c) its so thin that each coat doesn't really cover the wood
adequately, so you need a lot of coats to get a good protective layer
d) varnish breaks down in sunlight and decomposes
Can anyone tell me more about this? Is it acceptable to just keep
adding layers over the top before the bare spots show up?