Where does varnish go?

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?
Thanks. --riverman
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riverman wrote:
> A few months ago, I refinished an old Teak picnic table I picked up > for a bargain. <snip>
If it is really teak, it's oily.
After a while, the varnish loses it's grip due to the internal oils in the teak.
You can put a 100 coats on and still lose.
PLAN; A
Only thing I know that works, is to wipe down the teak with acetone, then apply a coat of epoxy TOTALLY encapsulating the teak.
Allow to dry for 24 hours, then lightly sand and apply another coat of epoxy.
Repeat daily unit you have 4-6 coats of epoxy, then allow to cure for about 10 days, then lightly sand and start applying coats of varnish that contains UV inhibitors on a one coat a day basis, sanding lightly between coats.
About 6-8 coats should do it.
Keep a nail polish bottle full of varnish and a ScotchBrite pad handy to repair scratches immediately.
Be totally paranoid about protecting tho table when ever anybody comes around.
PLAN: B
Screw it, let it go silver and enjoy life.
Have fun.
SFWIW, building a boat with NO external teak or any other wood for that matter.
Lew
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Plan B for me... Tom
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Oddly, insects like the stuff. I built a porch swing out of white Oak, put Spar Varnish on it and "Wasps" devoured the finish.
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Leon wrote:

So what was your solution?
Lew
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This was actually for a customer. I told them I did not guarantee the finish against mother natures creatures. Very strange, they would eat the finish completely off in one spot and expand that spot. It took about 1 year for the finish to be completely removed.
Since the finish was on a bench they chose to not spray repellents to defend the bench.
No solution. But like any outdoor clear finish, it should have been reapplied every few years although this finish was not lasting that long.
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riverman wrote:

It's called "weathering". And yes, it is primarily the result of sunlight...no sun no (or little) weathering. I made a teak dash board for my car in 1992, varnished it and have done nothing since. Still pristine. _______________

That's the normal method. You need to sand before applying new to remove the oxidized layer.
--

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Apparently windshields have some type of filter and or indirect light does not affect the finish. Some automatic tenting prescription glasses will not darken behind a windshield.
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Jim
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@swbell.net says...

Glass does cut a great deal of UV out of direct sunlight. Alas, not all of it. The jarrah inlay in my kitchen table has faded from purple to pale brown :-(
-P.
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says...

The angle and thickness may have a lot to do with it also. Sunlight through a windshield is not as much of a constant as a window glass in a house.
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Auto safety glass is a glass-plastic-glass sandwich. The glass doesn't block the UV, the plastic core does. Printers who use UV exposure lamps use glass plate holders, never plastic.
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