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!”