Perhaps I am missing something… <!—-><!—-> <!—->
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I have traditionally used 0000 steel wool for sanding in between coats. My latest project is in walnut, and I am worried about black spots (bad experience with oak…)<!—-><!—->
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I got some of those gray abrasive (scrubby) pads and frankly they don’t seem to provide anywhere near as smooth a finish the steel wool. <!—-><!—->
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Is this common?<!—-> <!—->
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Neil<!—-> <!—->
Replies
Neil,
The black spots from using steel wool on oak come from the steel reacting with the tannic acid in the oak. Walnut has essentially no tannic acid, so there should be no problem with black spots from the steel wool.
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Tschüß!
James
"I'm sorry, Dave, I'm afraid I can't do that...."
-- A.C. Clarke
Using steel wool for "sanding" (leveling) between coats is not a good idea. Using steel wool does not result in leveling, rather it polishes the hills and valleys, leaving a smooth, but undulating surface.
I think it's better to actually use "sandpaper" on a sanding block for leveling. (Actually, abrasive-coated paper.) I use 320-400 grit abrasive to level finish coats.
What finish are you using?
Since the surface has finish on it, it's a liitle hard to understand how the iron in the wool is reacting with tannic acid in the oak, unless you're cutting through the first coat of finish or there are lots of bare spots in the finish.
Rich
Your not getting spots from the tannic acid. Its called rust. The shards of steel wool embedded in the finish are exposed to water vapor migrating through the finish (no matter what the finish is) and they are rusting. That is why you should only use steel wool to rub out the final coat, never between coats.
Rob
EDIT: This post wasn't directed at Rich, I just hit his post to reply. Sorry.
Edited 2/28/2007 6:16 pm ET by Rob A.
Rob,
Hard to proove otherwise . . .but,
I've always used steel wool to apply oil/varnish finishes. After the first several applications, which I use a rag to apply and wipe dry, I then use 4-0 steel wool as the applicator/burnisher for the next dozen applications. This builds a thin but definite varnish film which should have steel wool particles as you suggest, which should rust.
I've never gotten rust spot one.
Thoughts?
Rich
Rich,
I don't know, maybe you just live right? I would be willing to bet though that the original poster is experiencing rust spots. It happens quite a bit.
What do you think?
Rob
I dunno. Certainly could be. That's what I said. But then it should be a common occurance with using steel wool all during the finishing process.
One would think. I must admit that I have never personally experienced it. But early on I heard so many others that had the problem that I just never used steel wool except to rub out a final coat.
I don't want to steal this thread, but has anyone else have experience with this one way or the other. It just makes so much sense that it almost has to happen.
Rob
Steel wool and walnut gives you ebonized walnut, because the tannic acid in the walnut reacts with the iron to form iron tannate.<!----><!----><!---->
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It's a pretty common procedure to dissolve steel wool in vinegar in order to stain Walnut. It gives you a nice ebonized look while preserving the grain.<!----><!---->
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It’s true that the oil in the finish should in theory, isolate the walnut from the particles that the wool sheds, but my guess is that some of it would react and I would rather not find out the hard way.<!----><!---->
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The real question is if these pads do as good a job as 0000. Frankly, the pads do smooth the surface but it doesn’t really shear the wood the way steel wool seems to.<!----><!---->
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Neil<!----><!---->
I use worn 150-grit paper on a rubber block between coats, then put a satin sheen on the final coat with maroon-colored pads that are held in a special pad-holder with hooks on it, made by 3M. Those gray pads won't cut diddly.
I buy my no-name pads very reasonably from Industrial Abrasives in packs of 10 (12?). I've tried other mail-order places for the nylon pads and gotten skunked with pads that contained chunkier grit that marred the finished surface. The Scotch-Brite pads provide excellent quality, but you'll pay more for the name.
Neil,
Part of your problem is the use of the gray synthetic pads -- they're too coarse, corresponding more closely to 00 steel wool. The ones you want to use for rubbing out a finish are white which are the equivalent of 0000.
Michael
Take a look at Abralon pads. Use them on your ROS. They go up to 4,000 grit. The process is troublefree and the results are excellent.
Frosty
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