Strange finishing problem

[Vic Baron]

Any ideas on this one??

Making 4 dining room chairs. Using red oak that I bought rough and planed to thickness. Milled all the pieces and am finishing them before the glue up so NO glue or waxes etc have been applied to any of the wood.

Decided to use General Wipe on urethane in the dark mahogany color. I've used it before and like the color. Started with a tack cloth to clean all parts then wiped on a coat and immediately wiped down with a clean rag. Color looked fine.

Approximately 24 hours later I am putting on the first coat of the General Wipe on satin top coat.

On SOME of the pieces, the stain came off in splotches -exactly as you might get if you had glue on a surface. Remember, this is stock that I milled myself - I did not introduce and glue, silicone, etc to the surface.

Even though there is one coat of topcoat, I'm thinking I should sand down again and repeat the process BUT I'm at a complete loss as to WHY it blotched when it didn't wipe off when I applied the stain.

Any ideas? next time I'll just use a garnet shellac to get the finish.

Thanx,

Vic

[Swingman]

Tack cloth ... did you buy it?

Some of the commercial ones are waxed, and if you rubbed hard ....

[Leon]

General Finishes? Urethane stain? I thought that only Minwax had that kind of stuff. Anyway, most stains are meant to be wiped off after appication. If you introduced a varnish to a stained surface that was not wiped down after application you will often see this. Basically the varnish washes away the layer that did not pentrate. AND it often happens in such a way that you think you did something wrong during preperation, which you may have done unknowingly.

[Jim Weisgram]

[...snip...]

Hmm, polyurethane adhesion problems. I like the tack rag suggestion.

Other possible reasons? What was the temperature and humidity? High humidity can mean it takes much longer to fully cure, more than 24 hours. Lower temperature, same thing.

Another suggestion I've seen; sanding with stearated sandpaper can leave some material on the wood that affects adhesion.

More Google searching will no doubt find even more reasons the poly didn't adhere; it is a too common problem.

Well shellac is the finisher's friend. I use it for anything I can. If you want more protection, put poly on for the last coat. They say don't put poly over shellac but that doesn't apply if it is dewaxed shellac.

FYI, something that I recently read that makes sense to me, if you are building up several coats but want a satin finish, use gloss on all coats except the final coat, where you can use satin.. The flatteners used to make it the surface satin will cloud up the finish more than necessary.

[Vic Baron]

Hmm - possible tack cloth but it was a real old one that I bought a long time ago and have used before w/o issue.

Temps did drop into the 40's last night but it was up in the 70'sll day today. Started the top coat around 4pm - temp was 75.

out of about 48 pieces, about 12 have a problem - I'll take one and sand it down to bare wood and repeat the process and see what happens.

The discoloration looks exactly as it would if you spilled bleach on a dark fabric - looks like a spill and lighter than the surrounding area.

Frustrating.

[Leon]

Sounds exactly like the problem I almost always have with Minwax Polyshades.

[Leon]

To add to that a bit, my solution was to dab the stain back on and after drying, dabbed a layer or two of varnish. After the dabbed varnish dried I could apply successive coats of varnish in the normal way.

[Vic Baron]

Since there are only a few small pieces, worst case scenario, I could remill the parts - chair rails, etc but I think I'll try several approaches and see what happens.

I'll resand down to bare wood and try again

I'll try sanding the 'blotched' area and reapplying stain

I'll try your approach above also and just reapply some stain, although I did put a light coat of top coat on it already.

What is so frustrating is that there was no way to see this coming.

[Larry Jaques]

On Tue, 1 Dec 2009 06:56:49 -0600, the infamous "Leon" scrawled the following:

Yeah, a client made me use that one time on a project I built for them and I was aghast at the blotchy, brushmarked finish. They were OK with it. I tiptoed away and found a nice place to throw up. I won't make that mistake again.

-- Some days, it's not even worth chewing through the restraints.

[Kevin]

I had something like that happen when I wore some cheap disposable gloves while staining. Everywhere I touched it the stain wiped off. Ah well, at least it wasn't a great big hard maple entertainment center I had to sand down and redo. Oh wait, yes it was...

-Kevin

[Steve Turner]

I never have that problem because I never use the stuff.

[Larry Jaques]

On Tue, 1 Dec 2009 09:32:27 -0800, the infamous "Vic Baron" scrawled the following:

Sure there is. While doing the prep (wiping with lacquer thinner) look for differences in gloss. Water works for other adulterants, so use it to raise the grain and check while doing it, then dry it and use solvent to check again. It catches most crap easily.

I thought some nice clear cedar from the lumber yard was clean last summer and found out the hard way that it wasn't. I should have caught that in the prep, but I was too overheated to think that day and it cost me a couple more days of stripping, sanding, prepping, and repainting. That's right, the client wanted paint on $8/bf knot-free cedar wood! I cried twice over that job.

-- Some days, it's not even worth chewing through the restraints.

[Vic Baron]

Hmmm. Now that is an interesting concept. I always use those cheap nitrile/latex disposables from Harbor Freight.

[Swingman]

I use "Member's Mark" disposable nitrile gloves from Sam's when staining and have never had the problem.

[nailshooter41]

I haven't had any problems with the nitriles from HF. I cannot imagine affordable gloves from Sam's being much different from the HF models. i have used several boxes of the HF with no problems.

Just couldn't afford the ones made in the USA anymore. They are too expensive when you change gloves 4 - 5 times a day when finishing/ refinishing.

Robert

[PDQ]

BTB and maybe of topic: I have a box of those nitriles(?) used to keep = strange bugs (H1N1) at bay. They are definitely no good for removing = deck stain as the sodium hydroxide eats them up. ;-(

P D Q