wipe on poly

[Thomas R. Zack]

So, why thin polyurethane for wiping on. Why not use it as a wipe on finish right from the can , full strength?

[Bob Wingard]

Try it for yourself ... you'll soon learn the "WHY" of it.

[Scott Holmes]

It wil be too thick. You will not be able to wipe on a thin enough coat.

[Don Jarvie]

Are you using the can or the Wipe on Poly (assuming Miniwax)? The Miniwax Wipe of Poly works great and all you have to do is wipe it on. Very fool proof.

[Prashun Patel]

To add a little more detail:

At full strength, the product does not flow very quickly. It will start to dry and stop its attempt to level out pretty quickly. This means you benefit from a brush which can apply thick poly more uniformly than a rag; so there's not that much leveling that needs to happen. Also, a brush - when used properly - does not introduce as much air as does a wiping rag. Those air bubbles can get trapped as the poly dries.

Thinning reduces the viscosity. This allows the product to flow faster to level itself. Applying a very thin coat makes it easier for any air bubbles to pop before drying.

[Bob Wingard]

To add a little more detail:

Also, a brush - when used properly - does not introduce as much air as does a wiping rag. Those air bubbles can get trapped as the poly dries.

Thinning does 2 things: it increases the drying time, and reduces the viscosity. This allows the product to flow faster and longer to level itself.

That statement is SO untrue, I can't believe I'm even reading it here. The biggest advantage to thinned or wiping varnish is that the lower viscosity equates to much lower surface tension which allows the finish to get deep into the pores, displacing any air that might be trapped there. As more coats are applied, the pores fill up with resin until there is no more trapped air in them Thinning DOES NOT INCREASE drying time ... it significantly REDUCES it ...

[John McClanahan]

As a novice, I've produced air bubbles that stayed trapped in a thick finish. As a novice, I wouldn't consider Prashun's statement untrue. Your mileage may vary.

John

[Prashun Patel]

Bob-
I did misspeak. I apologize. My statement was WRONG and I edited appropriately after reviewing just now. Adding OIL increases the open time - not thinner. Many times I make an oil varnish blend which is equal parts thinner, varnish, and BLO. This does increase the open time, which is important if soaking and wiping off. My

As for the bolded statement in yr reply, what I meant was that a brush is more appropriate (maybe just for me?) when applying a full-strength varnish because you need to lay it on as level as possible because it will not flow and level b4 it starts drying. It's tricky to use a rag to wipe on an even enough full-strength coat that level properly.

[Howard Acheson]

>>>> I've produced air bubbles that stayed trapped in a thick finish.

Yes but, using the proper technique for applying a wipe-on finish you will be applying a thin coat. "Wipe-on" is mostly a technique. It is quite different from brushing and done correctly, no bubbles will result.

Here is an excerpt from the instructions published by the guy who was a early developer and advocator of the wipe-on technique:

QUOTE

The number of coats in a given day is not important. Important is to apply a wet coat with an applicator and merely get it on. Think of a 16 year old kid working as a busboy at Denny's you have sent over to wipe off a table. Sort of rub/swirl the the material on like you would if you were applying a paste wax. Don't attempt any straight strokes. The applicator should be wet but not soaked. The applicator can be a non-embossed paper towel shop towel, half a T-shirt sleeve or that one sock left after a load of washing. Once applied,leave it alone. The surface should not be glossy or wet looking and, if applied correctly, there should be no "brush stroke" type marks. If you have missed a spot, ignore it - you will get it on the next coat. If you try and fix a missed spot you will leave a mark in the finish.

Timing for a second coat involves the pinkie test. Touch the surface with your pinkie. If nothing comes off you are ready for another coat. If was tacky 5 minutes ago but not now, apply your next coat just as you applied the previous coat. Remember, you are wet wiping, not flooding. After applying the second coat, let it fully dry for 48 hours. Using 320 paper and a sanding block lightly sand the surface flat. Now, begin applying more coats. Do not sand between coats unless you have allowed more than 24 hours to elapse since the prior coat. The number of coats is not critical - there is no critical or right number to apply. For those who need a rule, four more coats on non-critical surfaces or six more coats on surfaces that will get abraded seems to work. Apply the last coat more carefully finish off by wiping in the direction of the grain.

CLOSE QUOTE

[Hans Braul]

Bob-
I did misspeak. I apologize. My statement was WRONG and I edited appropriately after reviewing just now.

Prashun,
You are a real gentleman. So often the response to a "schooling" such as what you received from Bob would be to start a cat-fight that can go on for pages. Thanks.

[Bob Wingard]

Prashun,
You are a real gentleman. So often the response to a "schooling" such as what you received from Bob would be to start a cat-fight that can go on for pages. Thanks.

I can appreciate your coming to Mr, Patel's defense as an impartial observer ... I admit I probably was a bit harsh in my comments. I strongly believe, however, that if one is posting information here as being factual, it should be correct. The statements I was critical of were completely wrong, and Mr. Patel came to realize that, for which he responded with an admission and even an unnecessary apology. On the other hand, if you, as a newbie actually took his advice and acted on it, you might have had a completely different view of his "gentlemanly" character. If you made a horrific mess of finishing an otherwise beautiful project, I think my comments would be mild compared to what you might have posted after such an incident. I have read many of Mr. Patel's comments here over time, and normally I can agree with most everything he writes, and I respect his opinion ... which is why I couldn't believe some of the comments in this particular thread. I jumped on it just to throw up a red flag in case the OP was possibly accepting them as factual. Now that it's all pretty much settled, you come in and criticize me for having criticized him ... I don't know if I find that more humorous or insulting ... not that it matters.

[Hans Braul]

Now that it's all pretty much settled, you come in and criticize me for having criticized him ... I don't know if I find that more humorous or insulting ... not that it matters.

You're right, it doesn't matter. I said nothing to criticize you, nor was any criticism intended. Sorry if I caused offense.

Regards
Hans

[James Spach SC]

I have lately been using the 3 - 2 - 1 method. 3parts paint thinner - 2parts poly - 1 part oil. Love the results... I use 320 paper to sand in the first 3 coats and then go to 600 after that (sanding as applied (wet))..

[Peter Kelly]

Bob-
I did misspeak. I apologize. My statement was WRONG and I edited appropriately after reviewing just now. Adding OIL increases the open time - not thinner. Many times I make an oil varnish blend which is equal parts thinner, varnish, and BLO. This does increase the open time, which is important if soaking and wiping off.

I've found you'll get a much more durable finish using pure tung oil and instead of boiled linseed with this method.
http://www.realmilkpaint.com/oil.html

Substitute the mineral spirits with citrus solvent that Real Milk Paint sells and you'll reduce your VOCs considerably.

[Scott Holmes]

Peter, exactly how did you determine that the pure tung oil mixed in to the oil/varnish blend is more durable than the BLO mixed in instead?

Pure tung oil is a terrible finish alone. Neither tung oil o nor BLO dry hard; both are more rubbery than hard.

If by chance you are using Formby's Tung Oil finish than I would agree with your conclusion... of course Formby's is an alkyd resin/soya oil VARNISH the only "tung oil" is the words printed on the label.