Replies

1. 
   HowardAcheson | Feb 09, 2004 07:44pm | #1

   You have to get rid of the dust in your finishing area. Many folks finish up their sanding and go straight to applying a finish. Of course, this will always be problematic.

   Here is what I do for the final coat. First I sand on my downdraft sanding table. Then I turn on my air cleaner, vacuum off the project and vacuum the all the wall, floor and other surfaces I can reach. Then I go out of the shop and leave the air cleaner running. A couple of hours later, after changing my clothes, I go back and wipe the project down with mineral spirits and without stirring up any dust, I begin to finish. Then get out of the shop until the project is tack free.

   I know it sounds extreme but if you don't follow some procedure like this, you will always have dust in the air which will settle on the finish.

2. 
   JBD | Feb 09, 2004 09:18pm | #2

   As a professional finisher and coatings chemist with two patents in polymer science, let me assure you of this fact:  Blemishes in a final topcoat hardly have anything to do with fine sanding dust.  I routinely would sand IN MY SPRAY BOOTH without blemishes. 

   I've spent many hours picking out the "nerds" as we call them, out of the final clear topcoat (after air hosing and tacking the surface) and discovered that about 90% of all the nerds that disrupted the surface tension of an otherwise glass-smooth top film are actually pcs of lint - tiny short bent hairs from the fabric of clothes.  Remember that the wet mil film of many topcoats can be as much as 15 mils, which is more than enough to absorb the average sanding dust particle of 50 microns (two mils across).  This means that its only the stuff that sticks up higher that ruins a finish.  These pcs that stick up higher are NOT going to be floating in the air very long, (large clustered duct particles), hence no need to worry about the sanding dust in the air, just need to worry about the lint that might be floating instead, which is combatted a different way.

   When I realized that lint was the major culprit, I began protocols that limited the dust in the air to graet success like removing my shirt, blowing all dust off my arms and upper body, and spraying the piece with my back to the spray booth, so that the air flow pulled clean air over the piece, not air that went past any clothes or me. 

   To translate this into your situation, Bob, I would:

   1. prepare a dust cover for the table top by making stands to prop up a large sheet of cardboard to cover the T-top, and get it ready to carefully and slowly place over the wet top a few inches above it. 
   2. Get your final finish ready to brush on (assuming you've layed down a couple sealer coats first - these coats don't need dust control protocols).
   3. Then blow/wipe dust off top, then walk out of room for a half hour to let dust settle
   4. then tack cloth the surface clean, and have your finish ready to apply. 
   5. Then I would apply the final top coat heavy enough to absorb much of the lint that will come mainly from your moving arm during brush strokes, so you might want to wet-down your bare arm and upper body. 
   6. Then lay the dust cover over.  If large enough particles are in the finish, you might be able to pick them out with the corner of a razor blade, then drip in one tiny drop of finish over the "crater" left.  Leave it to dry and don't be anal about further dust - can be rubbed out later

   You will ALWAYS have dust nerds dried into the finish no matter how perfect your dust control is (unless spraying top upside down - works pretty well), so learn to wet sand 1000 grit, then buff with automotive rubbing compound and final glaze.

   One trick I love is slicing off the nerd flush with the surface with a new razor, then cross-scraping with the razor, just before wet sanding.  With practice, you'd never know you took a razor to the surface.

    - JB

    

   "The furniture designer is an architect." - Maurice DuFrenes (French Art Deco furniture designer, contemporary of Ruhlmann)

   http://www.pbase.com/dr_dichro   http://www.johnblazydesigns.com

1. 
   creations | Feb 11, 2004 11:54pm | #7

   Thanks for the detailed response.  I tend to agree that most of the rough spots seem to be due to lint or hair (from the cat) that has come off of my clothing and settled onto the wet surface.  Although I have done a thorough cleaning of my shop prior to finishing I never gave much thought to what my clothing may be carrying.  I will try rubbing out the surface to see how much of this I can remove.

   Bob

1. 
   OneofmanyBobs | Feb 12, 2004 02:18pm | #8

   Put on the last coat upside down.  Helps slightly.  Run a humidifier.  Dust seems to be actually attracted to the wet finish by electrostatic charge.  Some materials and finishes attract more dust than others.  Finishing in very dry conditions does not help.  The old way was to hang a curtain around your work and wet the curtain.  I suspect this helped more from the humidity than by actually removing dust from the air. 

3. 
   Paul_Snyder | Feb 10, 2004 03:48am | #3

   Bob,

   If your rubbing out process does not remove the defects in the surface, the info in the article at this link has the solution - Rubbing Out a Finish.

   The article recommends using a sanding block and sandpaper to remove surface defects and level the finish but on flat surfaces I like to use Abralon pads on a random orbit sander. As long as the finish is thick enough to cut back level, the Abralon does a great job and is quick and easy. For a satin sheen, grey scotchbrite on a square palm sander is another labor reducer.

   Paul

4. 
   ArtHeft | Feb 10, 2004 03:32pm | #4

   Rkelm...lots of good suggestion here.  I can only add that you might try a finish that dries fast.  I have had very good luck with Quick 15 fast dry alkyd varnish made by Zinsser and sold at Sherwin-Williams stores.  It is tack free in 15 minutes.

   Art

5. 
   Gretchen | Feb 10, 2004 03:51pm | #5

   I suggest you use a wipe on varnish. It will dry quickly so that dust will not stick in it.

   Gretchen
6. 
   GHR | Feb 10, 2004 05:42pm | #6

   As others have said - use a finish that you can repair.