Avoiding Dust In Your Finish

This week’s question comes from Jason. He writes:

No one has ever answered this directly for me, and you are becoming my trusted source! :) It has to do with finishing and dust getting on the finish…I mainly use tung oil now and that fixes the problems since it soaks in and doesn’t sit on top of the wood, but in the past whenever I used polyurethane when it was dry the board felt bumpy and looked bad b/c of all the crud that settled in the finish…I have tried cleaning up the shop to the best of my ability and I can’t seem to keep dust out when using a poly or something similar…And if I sand it out and recoat, it is just back again…How do I get rid of this damn dust in the air???? Is there some trick I am missing, it drives me crazy and actually I stopped woodworking for a long time b/c I could never seem to get a decent finish which frustrated me to no end…I now have a better shop and I do have a Delta air filtration unit, should I leave that on when finishing??? I just figured it would stir up the airborne dust particles more…I thought maybe finishing in a different room, but even my bedroom has dust particles floating around, I can see them in the rays of sun coming through the windows…And my house isn’t dirty or anything, I always figured some dust is just normal always in the air…Help a frustrated brother out, lol…I appreciate any help you could give me on this subject.

And here was my reply:
“Hey Jason. Take a deep breath. We all deal with these issues so don’t get too uptight. There are a few tricks and some standard practices that should help you out. First, you should try to reduce the shop dust as much as possible. Vacuum the area thoroughly and turn on your ambient air cleaner the night before a finishing day. You are right about keeping the cleaner on while finishing. That will only stir the dust up and create more problems for you. Now if you really want to get crazy about it, you can even wet the floor down around the finishing area. This will cut down on the dust created when you walk around. I never really do this though.”

“Once the prep work is done, you can start your finishing. When using poly, you have a long cure time right? And that’s the problem. While the finish cures, dust settles in it. So one thing you can do is start using a wiping formula (if you are not already). The wiping formula is thinned with mineral spirits, and will dry faster than full-strength varnish. You may have to apply more coats to get the finish thickness you want, but that’s a small price to pay for less dust-nibs. Now once the finish is dry, you should lightly sand with 320 grit and apply the next coat. Repeating this process, you won’t have a problem until the final coat (as you found out). For the final coat, I typically thin the varnish as much as 75% with naptha instead of mineral spirits. The naptha flashes off quickly and dries before lots of dust has time to settle. If you can spray this coat with an HVLP system, you are even better off. Now once this last coat dries, it is inevitable that you will have an occasional bump. I take care of these with a light touch of 2000 grit automotive sandpaper. The 2000 grit is aggressive enough to flatten the nibs but fine enough not to scratch the finish. Don’t rub too hard. Just a few light passes will do the trick. That should leave you with a nearly flawless finish. And with practice, the results get better and better. Hopefully that will put you on the right track. Good luck!”

Category: Finishing

Comments

  1. The info you gave is perfect. I even once tried to use a piece of tarpolin suspended about 1 foot over a huge panel i was finishing some years back. It actually worked, but it took forever to setup. I also use wipe on poly, and do thin it on the first and last coat.

    Another idea is to have a higher temp in the shop as well. A temperature of 10 degrees higher than standard room temperature also helps the finish cure faster.
    Also you may want to try water-based finishes! In some cases, they can dry faster than shellac finishes. I find that major horizontal surfaces (tables, chests, dressers, etc.) need tough oil-based finishes. But the sides (gable ends), i use water based with great results.

    The smell is greatly reduced, and you don;t have to wear a mask (you should always anyway)! But with oil, it can be unbearable in a small space.

    Peace

  2. Great info. On oil poly you might want to use water when you use the 2000 grit sandpaper. It is wet/dry super mega fine stuff and can give you a mirror like finish with high gloss poly. Use a spray bottle and lightly mist the surface, this will keep the paper from clogging and it acts as a lube for the sanding. Sanding block/sanding dowels should also be used wherever possible.

    LQQK

  3. David Caskey,MD September 13, 2007

    I had a large piece to finish and obtained a very good result by simply hanging some clear plastic sheeting from the ceiling. This worked great and was simple to construct. From watching the painters who work on my house, I get the idea they do the same when applying varnish and poly.

  4. Mark Salomon September 13, 2007

    I use a coat or two of brush on poly sanding with 400 between coats (you really need to let this dry or it will pill up when you sand if it’s not dry). I’ve found that wipe-poly by itself doesn’t give enough of a base unless you put about 10 coats on and I don’t want to spend this kind of time. To prove to yourself how little wipe-on goes on try measuring the amount of wipe-on poly that you actually use for a coat and and you’ll be amazed at how little goes on. Anyhow, after it’s dry wipe a couple of coats of wipe-on poly with a light 600 sanding in between. You can finish with a final wipe-on satin, a light rubbing with 0000 steel wool followed by wax, or simply a coat of wipe-on gloss poly if you want a higher sheen. Virtually no dust problems and a great finish.

  5. bobby russell September 30, 2007

    Good info guys , i would like to add a couple of things if you are using a sprayer and have the compressor or tubine have them outside the room and just before you spray or brush boil an electric kettle once or twice depending on the room size half an hour before you start painting .what happens is the steam rises and and when it falls it takes it the dust with it and helps a great deal with you finish. good luck..Bobby

  6. C Ed Wright (http://) October 4, 2007

    Dr. Caskey’s plastic attracts airborne dust via static electricity. Great if that’s the problem. That’s like planting dill near tomatoes to divert hornworm caterpillars (because they prefer dill to tomato plants!). However,

    Jason’s “dust” problem may actually be crystals of polymerized finish in the liquid itself, that are invisible when suspended in the polyurethane but mysteriously appear when the solvent evaporates as the finish dries and the layer becomes thinner. If no dust-control solution seems effective, this may be what’s happening, especially if it’s been around a while. In that event, simply filter the contents of the can into another, perfectly clean, container. Before returning the filtered liquid to the original container (if you choose to), you must first thoroughly clean all residual liquid from that can, because it will also contain some of those crystals. It might be easier to simply use a new empty can from the paint store/department and label it with a magic marker.

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