Removing dust nibs

[Eric Bayes]

When going through my finishing regimen on my test pieces, I've been sanding lightly with 400 grit sandpaper in between coats of waterlox to remove dust nibs. The 400 seem to scuff the pieces pretty good - to the point it turns white, which disappears when I remove the dust and recoat it. Is this normal, or should I be using a scotchbrite pad? If so, which color? Thanks for the help guys.

[Richard M. Wolfe]

I use 400 or 600 to knock down nibs on flat surfaces. The 600 naturally won't be as agressive as the 400 and also test the amount of pressure required to do the job. You can always go over it a second time. In corners, curved surfaces, etc I use #0000 steel wool....unless it's going to be a piece with waterborne finish. I'm not a big fan of scotchbrite pads. They seem to be more likely for me to round over the nib making it smoother but still there rather than removing it.

[Steve Schoene]

Dulling down the finish is the normal result of sanding, it's not a problem. In general, 400 grit is the finest sandpaper one should use between coats. I usuall use 320 grit, too fine you don't get enough "tooth" to assure a strong bond between coats of varnish. I agree with Richard that sandpaper works much better on such dust nibs than Scotchbright or steel wool.

[Eric Bayes]

What about on the final coat - how do you remove any dust nibs that may have collected after you applied the final coat. You wouldn't sand that down, correct?

[Steve Schoene]

Yes, I would, though probably I would start with a finer paper, about 600 grit. I would then go to about 1200 grit to remove the scratches from the 600 grit. From that point I would shift to some kind of polishing material, rottenstone for a gloss finish or pumice for a satin finish. Prepared rubbing and polishing compounds also work fine. This "rubbing out" is the step that makes all the difference between OK amateur looking finishes and finishes that surpass what comes out of furniture factories.

There is a catch however. You need a VERY light touch doing this on a wipe on varnish where the final film is so thin. If you cut through a layer of varnish you run the risk of revealing "witness" lines that look like faint topographical map lines. The cure, if it happens, is usually another coat of varnish.

There are things you can do to reduce the risk of cutting through. With a wipe on varnish you can apply the coats in groups of about three coats, with only enough waiting between coats for the first to no longer be tacky. This close spacing, needing no sanding in between, allows the coats to link together becoming one thicker coat as far as the witness lines are concerned. You can't do more than about three coats without stopping to let them cure overnight or you risk "trapping" solvent in lower layers. After letting a group cure, sand before applying the next group.

In addition you can make the final rubbout a bit safer by doing a more thorough sanding before the last group of coats to ensure a very level finish.

Does this look like a lot of work. Well, yes, it is, but after you have seen the results you are likely to be really impressed to see your work step up to the next level.

[Alfred Cole]

Normally I never give advice unless I have successfully used the technique myself but in this instance I'll break my own rule.

I recently read that one can remove nibs on a final finish by burnishing the finish with a brown paper bag folded into a pad. I want to try it but am too involved in workshop reorganisation at present. I offer it as a possibility and would be interested in feed back.

Jerry

War does not decide who is right. War only decides who is left.