Dust removal and tack cloths

Overview

Dust is the one contaminant every finish meets. Bob Flexner's advice in Popular Woodworking is blunt: a vacuum is the best tool because it is the cleanest, and a brush just kicks the dust into the air to land on your work later. Tack cloths and microfibre cloths have a narrower job, taking the last traces after the vacuum. The target is practical, not perfect: you do not need to clear every pore, only to get the surface clean enough that you cannot feel or pick up dust when you wipe a hand over it.

When to use

At every stage: after each grit in the Sanding schedule, after Raising the grain, after sanding a sealer or a cured coat, and immediately before the first coat of finish.

Materials and tools

• A vacuum with a soft brush attachment.
• A microfibre cloth with hemmed edges. Kevin Southwick (Popular Woodworking) says it picks up fine dust as well as, if not better than, a tack cloth, and unlike a tack cloth it can be washed and reused.
• A tack cloth or "sticky rag", for very light dust only.
• Compressed air, only if you have a good exhaust system such as a spray booth (Flexner).
• Mineral spirits, naphtha or alcohol, for a final wipe that doubles as a flaw check (see below).

Steps

1. Vacuum after every grit. Flexner says to remove sanding dust before moving to the next finer paper, whichever sanding method you use.
2. Do not use a tack rag at wood level. Flexner: tack rags load up too quickly with the large amount of dust created there. Keep them for the small amount left after sanding between coats of finish.
3. Prefinishing plywood. Southwick removes sanding dust with a tack cloth or vacuum, and after sanding the shellac sealer coat uses a dampened microfibre cloth (Finishing sheet goods (plywood, MDF, MDO)).
4. Spot check. Run a bare hand over the surface; look along a raking light. Flexner also wets the surface with mineral spirits or alcohol to show scratches and glue, but avoids mineral spirits before a water-based finish.

Common problems

• Specks and nibs in the finish. The sources opened give no formal diagnosis. Sanding a cured coat with #400 or #600 paper smooths it (Flexner; see Sanding schedule), and Rubbing out a finish covers the final coat.
• Dust in the pores shows under the finish. Flexner says you will not see a difference under a finish, or under stain and finish, so stop at the hand test.
• Tack cloth leaves a smear. The sources opened do not discuss residue from tack cloths. Check with a test on scrap, particularly under a water-based finish.

Safety and environment

Fine wood dust is a respiratory hazard: vacuum, do not sweep or blow it around, and wear a respirator. Cloths used with oil finishes or solvents can combust: see Oily rag safety. Where compressed air is used, make sure there is exhaust so dust is carried away, not just redistributed.

Related

• Sanding schedule, Raising the grain, Degreasing oily woods
• Spraying with HVLP for booth air flow
• Water-based polyurethane, Oil-based polyurethane for between-coat sanding