Finish contamination! Were stearated abrasives the problem? - created 03-27-2004

Clift, Tom - 03/27/2004.22:13:31
Subscriber from the Inland Empire

I’m having a problem with finish contamination on a dulcimer I’ve built. Here’s what I did: I sanded the walnut body and fingerboard to 220 and applied several coats of Deft with a brush to seal.

Everything was fine to that point. Then I sanded level and applied some more coats of Deft. I began to notice a few small “bare” spots. Not really bare, but not as much finish as the rest of the body. After applying one coat, I watched for a while and saw the finish slowing migrate away from the bare spots.

After exchanging posts with Deb, I found that I was using stearated sandpaper, Norton 3X. Now there’s nothing on the paper itself or on the package to indicate this. I only found out what I had by going to their website. I cleaned my entire finishing area (a table) and sanded the whole dulcimer back to bare wood using some (hopefully non-stearated) aluminum oxide paper. I noticed a big difference in the loading right away. I applied a couple more coats of finish and noticed the same thing happening again, only in larger areas this time.

I might add here that I keep my hands, brushes and the surrounding areas as clean as I can. I wiped with naphtha on a clean rag between coats and am on a first name basis with my tack cloth.

Now for the questions: Is this a typical case of stearate poisoning or something else? Is anyone else having this problem? Will this contaminate the brushes I was using? Or is it just in the wood? Can I seal the wood with something (shellac maybe?) and continue with Deft? If I brush on some shellac, or whatever, will it contaminate THOSE brushes too? Is stearated paper only a problem with nitro, or other finishes as well? Are there other issues I don’t know about?

I know several people have sung the praises of 3M gold papers and Mirka also. Are they stearated? Is there any way to tell if a paper is stearated and not labeled as such?

That's exactly the problem I had when I used stearated paper, it's called "cratering." The craters were about the size and shape of a thumbprint. Stearates change the surface tension of lacquer and it will flow away from the contaminated area. It wasn't the first thing I tried but eventually I stripped and refinished, and didn't have a problem the second time.

I'd strip the instrument down to bare wood, thoroughly vacuum and clean your work area, wipe all surfaces down with some solvent-dampened rags, changing your clean-up rags frequently. Seal the wood with shellac you apply with a new, clean brush or fresh pad. And, if you were applying the finish with a brush that you've been brushing on the instrument and then dipping into the can, you may have contaminated your entire can of Deft. I'd get a fresh can. Or just French polish or shellac the dulcimer and forget about lacquer all together.

The gold sandpapers that I've seen for sale in the Grizzly catalog (according to their blurb) are stearated as well. Where would on find non-stearated paper Deb? as I've either seen it mentioned as stearated or else they say nothing either way.

I agrre with Deb that you've probably contaminated the cans of finish as well as the brushes though, time to restock. :-(

The only stearated paper I ever bought was one pack of really, really nice 500 grit paper that was a grey abrasive in wavy patterns on the sheet. It cut beautifully. The stuff I use is garnet paper up to 280 grit, then black wet-or-dry from there. I don't think those are ever stearated.

Cool. I have some 120G Al-Ox that looks like that, which turns black with use, and some heavy grit garnets, the rest is either the w/d or other al-ox. I did get a similar problem to this myself with brush on minwax water based polyurethane, but I think it was because I didn't get the soap completely washed out the brushes when that happened. :-)

I don't have any problem with contamination in my can. I've never been that happy with the viscosity of Deft and I pour a small amount into another container and thin it down some. I am concerned about the brushes though. I spent a bit for quality with these and it would be a shame to have to trash them. Perhaps they'd be suited for another finish that wasn't affected by the stearates?

I have a couple of sheets of that gray paper similar to what you're talking about. It's 3M Tri-M-ite, fre-cut, open coat. Cuts like the devil. I checked with 3Ms website and they say that it's silicon carbide and it IS stearated, though nothing on the sheet would tell you that. I got these sheets from LMI.

I don't know enough about stearate contamination to tell you. The 3M Tri-M-ite black silicon carbide wet-or-dry is what I like in the higher grits, and I've never had a problem with it.

Maybe one of our more technically-minded members will come along and explain the world of stearates as it relates to migration and finishes. I did a Google search and was drowning in the sheer number of technical papers that are out there. It would take days, if not weeks, to read them all and you still might not find the required info.

Since the stearates cause such a problem, you'd think that 3-M and other manufacturers would more plainly label it. Sure would beat the heck out of ticking off so many people after they have a problem. I'm off to check the 3 25-packs I just bought.

I looked around the web, and stearated abrasives are often mentioned with silicone as being a problem in finishing, both with nitrocellulose and water-based lacquers.

Ahhhh! I have Norton "3X" papers. No mention of stearates on the packaging, but I checked their website and sure enough,

]"3X also incorporates an advanced stearate (anti-clog) coating for exceptional resistance to clogging or loading during sanding."

Luckily I only opened 1 of the 3 boxes and will return the other 2 just to play it safe.

OK, so far stearated papers are:

* 3M Tri-M-ite, fre-cut, open coat

* Norton 3X

I've used a lot of stearated papers of different brands and have never had a problem with a solvent based finish. We're talking Deft nitrocellulose lacquer finish, thinned with lacquer thinner here?

BTW, Norton Champagne is about the best general purpose wood sanding paper I've found. I think it's stearated.

So have I. I've sanded with 3M tri-M-ite both dry and wet for years, never had troubles.

I had a little trouble on the last things I sprayed. A friend had given me some nice cloths that he got from a plating factory where he works, they wrap the finished products in these fine soft white cloths. I was wiping with one after wet-sanding and before the last coats and I got cratering- I think there's some junk in those cloths!

Howard, yes, Deft gloss nitro, thinned with lacquer thinner. I've done this several times, from the same cans, with no problems at all. The only change I made was my 220 and 320 paper. Everything was fine until I levelled. I don't know if Champagne is the same as the yellow 3X that I have, but I agree it's superior paper.

So it's possible I got contamination from another source, but I'll be #%&^!! if I can figure out where.

Unless you wear a fresh pair of gloves each time you touch the thing during the finish process (I don't), it's all too easy to inadvertently get some small amount of contamination on it and cause fisheyes. Sometimes you may even have to use fisheye preventer if the problem is bad enough.

From what I've been reading online, whether or not you get contamination may depend on the amount of stearated material that gets deposited on your surface. I did find one article (by Jeff Jewett?) that said never to use stearated sandpaper with Target PSL.

I've used the 3-M Gold on several projects, both on bare wood and in between lacquer coats and never had a problem either. Maybe just good luck, maybe Thomas' problem is silicone or another contaminant.

Mike, I can safely say there's no silicone involved here. I don't even have any in the house. I make an effort to keep only the substances involved with any given operation out in the area. This has really got me bugged.

I found mention (as has Deb) that stearates cause problems with nitro and waterbourne finishes, yet Howard and Mark say they have no problems. I don't doubt that, as this is the first time I've had a problem and I've used this particular batch of papers and finishing materials on other projects with no negative consequence. But it still makes you wonder. I really wish we could get a few more folks in here with some more anticdotes and compare stories.

I have a feeling that lots of people who have this problem don't know they're using stearated papers and have no idea what caused it. I do know that the only time I used stearated paper I experienced cratering, and never used stearated paper or had this problem again.

If there's one thing we all need to learn with regard to wood finishing, is to learn to think on your feet, and sometimes quickly.

Nothing is the same way twice, and never so for two different persons or shops.

Wood finishing is the most unpredictable process I've ever been involved with, bar none!

a perfect example is a few days ago, on the 4th coat on a new neck, the finish(waterborne) suddenly decided it didn't like me. It looked a bit odd when i shot that coat, so I went back into the booth some 5 minutes or so later, and all the finish had just sat on the surface, and now looked like thick veins of blue running all over the place! Having seen just about everything that could ever happen with wood finishes, I didn't think twice. I grabbed paper towel, and wiped the neck down, but didn't try to smooth it at all, just wiped it to get the "wet" finish off there. I grabbed the gun, and now shot a light, dry coat over top of the mess right away, and it was fine. The following coats all went well after that, and 36 hrs. later, it all buffed to a great gloss(this is a quick finish!).

Lesson: I could sit down, write the chemist who makes the stuff, and we'd brain storm for a week trying to figure out what went "wrong", but, why bother. The "fix" was simple, and I knew immediately what to do: wipe it off, leaving some on, and spray a dry 'barrier coat', then keep on keeping on.

I've given up trying to understand it all, and now just do what needs to be done. Life is much, much simpler today

One thing that has not been mentioned is storing your sandpaper. I store mine sealed up, I only take out what I need at the time. It keeps the chance of contaminates getting on it very low.

How did you wash out your brushes or whatever you used to apply with? Maybe you missed something there. I've had that happen to me recently and just gave a light leveling sand and put on another coat fixed it.

Well, for another data point, I use 3M Gold papers between coats of nitro (followed by a wipe with napthpa) and have never had a problem... so far.

Bob, what is printed on the back of those papers? Stock numbers or whatever they call those things. It would help me a lot.

Thomas, looking at the back of some P600, it says:

3M

216U

Production RN

Paper A wt.

Open Coat

Fre-Cut

For those who might be interested, you can get it from Lee Valley (through P600) and Homestead Finishing (through P800). I follow the P800 with micro-mesh 1800 and 2400 before buffing.

For smaller quantities, StewMac and LMI also sell the same paper, but most well stocked auto body shops will, too.

I've recently discovered P1200 in a shop up here, and it is really nice to use after the P800.

Unless they started carrying it recently (or I missed it), LMI doesn't show THIS particular paper on their web site (they have plenty of others).

Stew-Mac does indeed, and interestingly, they state that the no-load coating on this stuff is non-stearated...

I just invited Jeff Weiss to pop in here and tell us what he knows about this, since I've seen some references about *not* using stearated papers with Target PSL on the web.

Very Interesting about the 3M 216U. I couldn't find it at the US website. I had to go to Canada, but they list several places in the US where it's sold. Here's their description: "Premium aluminum oxide mineral on a standard A weight paper backing, with load resistant coating." No mention of stearates, but you wonder.

RP, I hadn't thought of paper storage. I keep mine in a large plastic baggy in a drawer. I only take out what I need at any one time. I guess there's a chance that the remainder of a sheet could be contaminated, but I'm still not sure by what.

Dennis I clean my brushes with the appropriate thinner, in this case, lacquer thinner. Then I wipe them with fresh cloth and put them in their little covers and back in a drawer.

Tests I'm doing right now, (thanks to inspiration from Mario) are showing that the brushes are okay, but I really won't know til later today.

Deb, it will be good to hear what Jeff has to say. He's always seemed to be very informative and forthright. Thanks.

Premium aluminum oxide mineral on a standard A weight paper backing, with load resistant coating." No mention of stearates, but you wonder.

Well, if these papers are stearated, I've never seen ill affects from it. Been using the stuff for at least 6 years now, nearly exclusively. I've never had a cratering problem like was described here.

I’m certainly a bit of a novice compared to many here (finishing #’s 9 and 10 right now) but this is what I have found and use. Each grade of the 3M “Production Fre-cut Gold” papers that I use have “216U Production RN Paper A wt Open coat Fre-cut” and “Made in Canada” printed on the back of each sheet, no matter the P grade or grit. I can only assume that these numbers are mean something to he folks at 3M. The part numbers for the 5 packs that I get from my local auto body paint store are,

P180 N.32545

P220 N.32544

P320 N.32541

P400 N.32539

The 800 Grit that I use I get from Stew Mac (Part # 5101) and it is the same 216U line. Stew Mac doesn’t sell it in the 5 packs and thus no similar part #. I also use the 3M Pro-Pak Premium 150 and 220 grit papers for bare wood sanding. This stuff is green, non loading, and has a durable C grade backing and each grit has 3M 235U on it (and “made in the UK”. This stuff lasts and lasts and I get it at Orchard Supply Hardware but have seen it in most larger hardware stores. So far I have had no problems with fish eye or cratering. I generally spray nitro and have used Pre-Val spray units but recently stepped up to an el cheapo HVLP conversion gun and just unpacked my buffing wheels from Stew mac yesterday.

Hope this helps somebody.

Rich

Well just for the heck of it I called the 800 number on the back of my 3M paper pak and “Erick” in 3M’s industrial abrasives division said this… all of the 3M “Fre-Cut” line uses stearate as a clearing agent (thus non loading). He also said that all non loading papers from other manufacturers use stearate as the unloading agent and that the only way to get away from stearate papers is to use a wet-or-dry type paper and either use it dry and live with it loading or wet sand with water or your lubricant of choice.

Well, that’s the word from 3M at least!

R

There are different stearates, I believe. The problematic one is zinc stearate, right?

Did you ask if they used the same stearate on all the products? I bet if you call again and get someone different, you'll get a different answer...

I haven't had anything to add to this lately because I've been waiting for contact from Deft, 3M and Norton. I emailed them to ask there were any "known issues" regarding nitro, waterbourne finish and stearated papers. They each replied in the negative.

After much research and testing here, I still haven't come up with a direct source for my problem. I'm guessing that the guy I see in the mirror had an awful lot to do with it though.

The testing I've done seems to indicate that there's no problem I can duplicate with my paper, brushes, thinner or naphtha. Everything seems to be normal now. I wish I could report that I found and corralled the culprit.

Thanks to everyone who contributed to this discussion. You helped a lot, even though I wasn't successful in my quest.

Maybe someone in the neighborhood was fooling around with some sort of silicone or something and some of it happened to see you were finishing a guitar and decided it'd be fun to land there and drive you nts? :-)

Like I've said earlier in this thread, Thomas, you'll just need to learn that you can't learn everything that needs to be learned about learning about wood finishing.

I drove myself nearly buggy trying to understand it all, but at the end of the day, you just have to do what needs to be done, and trust that sometimes, for no reason known to man or beast, it'll go wrong. Just shrug it off, and continue.

Yeah Mario, you're right. After the earlier post you refer to, I just went ahead and sanded back to wood (again) and sealed with shellac, like Deb had suggested. Everything else has been "in addition to", so to speak. I was just trying to avoid committing the same error(s), whatever they ended up to be. I'm not trying to learn everything there is, no hope for that. I don't have enough time left.

Currently I'm putting on some coats of Tru Oil. I'd never used it before and I was interested to see what it does. Looks okay so far.