So when is the finishing finished?

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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.
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Greg Guarino wrote:

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.
--

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On 3/18/2013 7:15 AM, dadiOH wrote:

Just to be clear, I took "regular" (not "wiping") MinWax Satin Poly and thinned it down.
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On 3/18/2013 8:28 AM, Greg Guarino wrote:

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.
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On 3/18/2013 10:04 AM, Unquestionably Confused wrote:

thinned) and thinned it further. I make no claim that three coats is "enough" because I don't know; hence my original question.
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"Greg Guarino" wrote:

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
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On 3/18/2013 9:43 AM, Lew Hodgett wrote:

+1 (more coat) ;)
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On 3/18/2013 1:51 PM, Swingman wrote:

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?
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Four coats is generally the cutoff point where the need, or lack thereof, for one more coat becomes a gut feeling.
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"Greg Guarino" wrote:

What does your gut tell you?
By your own description, you are applying 1/2 coat at a time.
Lew
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On 3/18/2013 9:35 AM, Greg Guarino wrote:

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<g>
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Greg Guarino wrote:

Anything can be improved with just one more tweak.
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Anything can be improved with just one more tweak. :-)
Hey! You're right!
...until that one more tweak breaks something... again.
Puckdropper
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Make it to fit, don't make it fit.

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On Sunday, March 17, 2013 9:41:13 PM UTC-7, Greg Guarino wrote:

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.
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On 3/18/2013 6:48 PM, SonomaProducts.com wrote:

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.
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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 <<easily>> 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
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On 3/19/2013 10:08 AM, Swingman wrote:

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.
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On 3/19/2013 2:58 PM, Greg Guarino wrote:

Nothing else matters ... absolutely _nothing_. ;)
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On 3/19/2013 6:13 PM, Swingman wrote:

+1
My take, too...it's not a for-sale piece where he's got to worry about a customer down the road.
And, time will tell if there's a problem of insufficient thickness and it'll be soon enough then to touch it up...
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What could be more true?
If you are happy and the finish hits all your requirements, then you are in the perfect spot. I have seen folks finish wood projects with non boiled linseed oil mixed with some kind of solvent or more resins and be thrilled. Looked great, and for the use of the piece, it was a good match.
No doubt you can match the finish to the project without help. I hope you didn't think I was lecturing; not my intent.
BUT.... (had to be one, right?) if you have a test piece of the same wood with the same finish and amount of coats on it, then you can easily test for final coat durability and appearance. You can add another coat as needed, or if it fits the bill the way it is, you are finished. (No pun intended...)
Robert
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