Buffing out a lacquer finish

      Finishers share their secrets for achieving a hand-rubbed lacquer finish. September 6, 2000

Q.
Can anyone help me with the proper procedure for buffing out a nitrocellulose lacquer finish? I'm interested in using rottenstone, pumice and oil.

What is the proper sequence and technique?



Wet-sand with progressively finer grits of sandpaper. It's up to you how fine you want go. You could stop at 400 grit or go up to 600 grit, 800 grit, 1000 grit, 1200 grit 1500 grit, 2000 grit, or 2500 grit. Let's say you want to wet-sand up to 2000 grit. Start your sequence with either 400 or 600 or 800, depending on how much orange peel or pebbliness you need to sand smooth. Then go to 1000 grit or 1200 grit, then 1500 grit, and then 2000 grit.

Use a sanding block, not the flat of your hand.

Then mix up a slurry of pumice. Then you can finish off with rottenstone. Rottenstone is finer than pumice.

When you wet-sand, use a squeegee to check your progress, and check that progress often.

You can use a sanding lubricant made from Murphy's Oil Soap diluted with 75 percent water or more. Or you can use mineral spirits, mineral oil, naptha, or combinations of any or all of those three petroleum distillates.



Are you looking to polish to high gloss or to achieve a rubbed look? If you are doing a rubbed look, short-nap wool carpet works great for rubbing. I don't like using oils to rub with, they just make a mess. I use flax soap, woolwax, or vegetable oil soap as a lube, mixed with water.
Bob Niemeyer, forum moderator


When you say "short-nap wool carpet," do you mean the stuff that we walk on? Could you give me some details how I would use this? I cannot imagine it (I lack the creativity for that kind of mental exercise).

Do you load the carpet up with lubricant or polishing compound? Do you back it against a flat block? And so on...



Bob, I'm actually just trying something new; maybe I shouldn't try to fix something that isn't broken. My finish is good, no orange peel or pebbliness or anything like that, I just want to make my finish look more uniform.

I used a semi-gloss, but I want maybe just a little more sheen. I was curious about using pumice, rottenstone and paraffin oil, and got a response, but am still unclear as to how to apply the "slurry." Do I use the fine grit sandpaper or a rag?



When using pumice (and then rottenstone), a slurry is made by mixing the liquid vehicle with pumice (or rottenstone). Take a small container (those Rubbermaid food storage containers work nicely), and add some lubricant. The lubricant can be an oil-based petroleum distillate or a water-based lube. You can even use straight water with no soap. Then dump in a quantity of powder (pumice or rottenstone). There is your slurry. Mix it to the consistency of pancake mix, maybe a little thinner.

You can rub this abrasive slurry with a rag. But even better than that is to use a large, flat piece of hard felt. Dip the felt in the slurry (or pour some on your surface) and rub in very straight lines. That means you should not arc your rubbing stroke like a rainbow or windshield wiper.

Another method of application is a rubbing brush. I have only heard about this, as this is an old-school method and I had to learn everything on my own. Anyway, the brush resembles a shoeshine brush. I think that these are available online at Ron Ashbey's Liberon.com website. He can also give you tech support on using this method of applying pumice and rottenstone.

It is my understanding that factories are still using pumice and rottenstone in their cutting sequences to achieve certain sheens (to be more precise it is the "look" of certain sheens that they are using them to achieve). But I think that they are using these abrasive materials with pneumatic dual-pad rubbing machines like the ones made by National Detroit and Stuhr (Cooper Power Tools).

It is hard to replicate by hand what these pneumatic machines can do to a finish. Difficult, but not impossible.

I hope that explains a little more. Now let's wait and learn about the artful use of carpeting in the rubbing out of a finish.



For years our shop rubbed all dining table tops. Yes, they looked wonderful, but a couple months later we would get the call to come out and re-rub the top due to mars in the finish. It's like those nice black pianos that are rubbed out; just dust them across the rub and they look awful.

About 25 years ago we started spraying all the final sheens, and the tops held up much better -- no re-calls. What also helped is that we added a slip additive to the last coat so things would slide and not scratch the finish as easily. Now the only time we rub anything out is if it was that way when it came in.

As for the carpet, yes, it is the stuff we walk on. Just get some good, short-nap commercial-grade wool carpet. Cut it to about 4 by 10 inches, then trim back the backer, because even a thread from it will ruin a rub-out if it works its way underneath.

Soak the carpet to get it wet in some soapy (woollube) water, sprinkle a little pumice/etc. on it and rub away in nice, long, straight strokes. You can also place this on a Sundstrand inline sander to do a nice fast rub.
Bob



Go to www.mimf.com and check out what the guitar makers are doing with rub-outs. Guitar finishes are the ultimate in gloss clear and colored finishes. Makes pianos look like non-skid boat decks.


I'm one of those guitar makers (actually I make mandolins), and before I built my very cool buffing system, I got great results using an off-the-shelf auto polish product called Scratch-Out. From the look of it, I'd guess it's rottenstone in a suspension; so fine that it made no difference whether I moved the pad in straight lines or circles. 'Course, I'm working on very small areas (not like a table or piano), and don't know your project.



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