So when is the finishing finished?

Life has gotten busy and my bookcase project has slowed to a crawl. But I managed to get three coats of wiping poly on two face frames this weekend. I used satin poly cut roughly in half with mineral spirits. I like the look. Does that mean I'm done? Oh I'll probably rub them down in a few days, but what I'm asking is if there's any reason to add more coats (for protection?) at this point if the "look" is already what I want.

Reply to
Greg Guarino
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Wiping varnish is thin naturally and three even more thinned coats doesn't afford much protection; however, a bookcase doesn't *need* much protection so stop when you like it.

FWIW, I figure four coats of unthinned oil poly for floors, three for anything else that gets some wear. With brushing lacquer I usually use three, sand heavily and then two more. For outside stuff with alkyd varnish, 6-7.

Reply to
dadiOH

Just to be clear, I took "regular" (not "wiping") MinWax Satin Poly and thinned it down.

Reply to
Greg Guarino

Yeahbut.... thin is thin. Does it make any difference whether you thinned it or MinWax did? Granted, you may not have thinned it as much (or maybe you thinned it more), but when all's said and done, you've wiped on a thinner coating than you'd have laid on with a brush or spray.

Reply to
Unquestionably Confused

I think DadiOh might have thought that I had taken Wiping Poly (already thinned) and thinned it further. I make no claim that three coats is "enough" because I don't know; hence my original question.

Reply to
Greg Guarino

---------------------------------------------------- If you have to ask, you probably already know the answer.

Your gut rules.

If it were mine, my gut says 3-4 more coats.

No good reason, just my gut.

Lew

Reply to
Lew Hodgett

As Lew says, go with your gut. Frinstance... I finished an 8/4 solid oak surround for a bar top (think frame with the field being ceramic tile) ~ 27 yrs ago with a gel satin poly varnish. I gave it, IIRC, 3 coats with light steel wool and tack cloth in between coats 2 & 3. This was followed up by a re-coat, with MinWax wiping poly a year or so ago simply because I was touching up another piece in close proximity. Didn't need it but the whole shebang looks as it did when I first finished it.

So many variables come into play with your project (and all projects, really). Is it going to be exposed to direct sunlight? Are you using it or are the kids? etc.

In any event, if you think you're done with the face frame and sides, you're probably not quite done with the top of the shelves (think wear points).

IOW, go with your gut and common sense

Reply to
Unquestionably Confused

+1 (more coat) ;)
Reply to
Swingman

Do you mean 1 more than I have done (a total of 4) or one more on top of Lew's "3-4 more" (a total of 7 or 8)? In either case, is that because I do not yet have sufficient finish to protect the wood?

Reply to
Greg Guarino

Anything can be improved with just one more tweak.

Reply to
HeyBub

Four coats is generally the cutoff point where the need, or lack thereof, for one more coat becomes a gut feeling.

Reply to
Swingman

You're done.

After the second coat you have a finish that will last a lifetime unless it is a bowling ally or highly used table top or other high traffic surface. Poly is so damed tough once that first coat soaks in. the second starts bui lding. That's why when I do wipe, I flood the first coat with a brush, then wiper down.

Splash some water on it, you will answer your own question. It is now plast ic.

Reply to
SonomaProducts.com

"HeyBub" wrote in news:eoWdnXBgg- p489rMnZ2dnUVZ snipped-for-privacy@earthlink.com:

Anything can be improved with just one more tweak. :-)

Hey! You're right!

...until that one more tweak breaks something... again.

Puckdropper

Reply to
Puckdropper

------------------------------------------------ What does your gut tell you?

By your own description, you are applying 1/2 coat at a time.

Lew

Reply to
Lew Hodgett

a bowling ally or highly used table top or other high traffic surface.

Not necessarily.

"Thinning", which he admitted to doing by approximately 50%, simply means the layers of poly he applied were 50% thinner, meaning more layers/coats are need to be applied to reach the same level of protection as the unthinned product.

When contracting for a polyurethane hardwood floor finish I spec four coats when "thinning" up to a maximum of 25%.

In his situation about the only benefit of thinning the poly is faster drying.

Reply to
Swingman

For things like this my rule of thumb is to apply two more coats than it takes to end up with a flat finish... For example, if it takes 4 sanded coats to get the finish flat and the grain filled then I add two more. This as the finish can be real thin in areas once flattened so the two additional coats gives at least that much finish on the whole surface.

The species of wood influences this to a great degree... in my experience red oak takes a lot more coats to level and fill than does cherry or maple... walnut is generally somewhere in between.

Note that I only use a thinned coat for the first coat... everything after that is not thinned. With thinned coats for all coats your build will be less per coat so more will be needed...

John

Reply to
John Grossbohlin

With thinned coats for all coats your build will be

It is not really appropriate to build for a flat surface using a film finish (varnish, lacquer, shellac, poly). If you want flatness then use grain filler. Finishes that thick will crack\craze over time most likely.

If you are applying enough finish to flatten red oak you have developed a slab of plastic over the wood.

I finish cherry with a few coats of wipe on poly and until I wax it, you can still feel the grain even after sanding the wood initially with 320.

Reply to
SonomaProducts.com

s it is a bowling ally or highly used table top or other high traffic surfa ce.

Not necessarily, indeed.

Important to remember here is the method of application. I read this over and over here and this is what I get from it. "I flooded the surface and wiped off all the finish I could until it looked smooth." Using jersey cloth you can get the finish left behind to 1 mil. of thickness. Using the average MSDS data, when the carriers and solvents leave the unthinned product, the coating will shrink in thickness about 66%.

So if one has thinned it further on their own, they will get 1/2 (from thinning at the shop) the amount of 2/3rds thickness less (remaining thickness after normal drying of unthinned product), or 1/6th the amount of thickness recommended by the manufacturer.

You now have what is known as a "dust coat". Further application of thinned product in the same manner will increase the thickness only marginally, so one may now have as much as 1/3 the amount of finish recommended by a manufacturer. But really, do you?

Probably not. The initial coating of finish will get more "traction" and will more readily adhere to the surface. However, the second coat will face a smoother, almost sealed surface and your application method of applying thin coats with a rag can leave as little as .5 mil coating behind. Figure in the shrinkage of the thickness after the solvents and carriers are gone...

I would submit to you that it is not an apples to apple comparison. In your situation, in my opinion, yours is exactly what is needed. Their are two huge differences. First, your flooring guy doesn't put down a few gallons of finish, then attempt to wipe off most of it. Flooring urethanes are formulated different, and without thinning they are almost impossible to get the correct layout of the product. They are made to be thinned, probably to the 20% range. (NO ONE could detect a 5% differential... probably not even a lab.)

Second, in an exactly controlled application as you speak, if you thin all coats 25%, but put on 4 coats the manufacturers application thickness requirement, you are exactly where you need to be when finished. Perfect.

Absolutely true. Thin coats of product do not provide adequate UV protection (think down lights, tables by windows, etc.) nor do they provide more than the smallest amount of abrasion resistance. These are finishes for extremely light use such as in the homes of older adults with no kids (and no drinking or eating buddies) and for pieces to be admired. Easy to put on, nice to look at, but little utility value.

Robert

Reply to
nailshooter41

With thinned coats for all coats your build will be

I guess this is an "it depends" situation and a matter of what is considered finishing and what is considered preparation... As such, perhaps I should have been more explicit. There are degrees of flatness and degrees of finish thickness. If a surface is really uneven, an extreme example being over-sanded pine, or hasn't been grain filled, then it would take a lot of finish to flatten it. I don't see either of those situations as a finishing problem, rather they are a preparation problem. On the other hand, well flattened and, if needed, grain filled raw wood can still have slight unevenness that can be flattened in the finishing process. Often times this slight unevenness is not noticeable until there is some finish on the piece. In these cases most of the finish is removed when sanding between coats and the final finish thickness is quite thin. Even under these circumstance I find differences across species of wood but I've never had problems in these cases...

On the other hand, dumping on a thick coat of finish, as you note, is a recipe for future problems! I've seen finishes so thick on some pieces that it looked like there was a piece of plastic over the top of the wood... I have to imagine that they didn't look so good as they aged!

Reply to
John Grossbohlin

As usual, I'm confused.

I have read that "wiping poly" is a popular and relatively foolproof method of finishing. "Fool-proof" has an attractive sound to it for a project with a lot of surface area to cover and me (yes, the "fool") in charge of the application. I'm at least theoretically willing to experiment with more sophisticated approaches, but not when I'm finishing the better part of four sheets of plywood (plus the face frames).

My sense of it is (or at least *was*) that the thinned product, coupled with the "wiping" application method, helps give a smooth even finish without the need for much expertise. No brush marks, no puddles, no bubbles. And in fact, I am quite pleased with the finish I got on the bookcase boxes. It's smooth, even and doesn't look at all "plastic-y" or thick. Could I really have gotten similar results with half as many coats of the full-strength poly? I have done that in the past and have not gotten as nice-looking a finish as I'm seeing now.

Reply to
Greg Guarino

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