What's inside
As an Amazon Associate I earn from qualifying purchases. This post may contain affiliate links at no extra cost to you.
Sanding between coats of oil-based varnish removes dust nibs and brush marks, then gives the next coat a fine scratch pattern to grip. The goal is a smooth, evenly dull surface—not to cut through the varnish or sand the wood again. Let the coat dry enough to sand cleanly, use fine abrasive, and keep pressure light.
When to sand
Follow the varnish label for recoat and sanding times. Temperature, humidity, coat thickness, and airflow all affect drying. A coat that feels dry on top can still be soft underneath; sanding it too soon may roll the finish into sticky crumbs or leave deep scratches that the next coat will not hide.
Before sanding, test an inconspicuous spot. The surface should feel firm and dry, and fine dust should come off rather than clumping or sticking to the abrasive. If the paper gums up, stop and give the varnish more time. Do not use a fingernail test on a visible surface: it can leave a mark.
Choose the right abrasive
For most between-coat work, start with 320-grit abrasive. Use 220 grit only to level noticeable ridges or roughness, and follow with 320 grit so the coarser scratches do not show through. For a very smooth final coat, 400 grit can be useful before the last coat, but it cuts slowly and is easy to overuse on edges.
A sheet of ordinary 320-grit sandpaper is inexpensive and works well for a small project. For larger surfaces, a fine-grit sanding sponge conforms to profiles and is less likely to leave sharp paper-edge scratches. Neither type needs to be expensive; replace it when it stops cutting cleanly or starts clogging.
| Abrasive | Best use | Main trade-off |
|---|---|---|
| 220 grit | Leveling distinct dust nibs or brush ridges | Cuts quickly and can leave scratches or cut through edges |
| 320 grit | Routine sanding between coats | Slower on high spots, but forgiving with a light touch |
| 400 grit | Light smoothing before a final coat | Slow; can polish the surface if used too heavily |
Sand the surface evenly
Work in good light so you can see glossy spots and scratches. On flat areas, wrap the paper around a firm, flat sanding block. Sand with the grain using long, light strokes. A block keeps your fingers from making dips and helps the abrasive contact the whole surface. On curved or shaped parts, use a sponge or folded paper that fits the profile without digging into corners.
Make a few passes, then check the surface with your fingertips and a low-angle light. Stop when the sheen is uniformly dull and the nibs are gone. Do not keep sanding just to create more dust. The varnish film is thin, especially over edges, corners, and routed details; these areas need only a pass or two with almost no pressure. A sanding block is helpful on broad flat panels, but a hand-held sheet is fine for small or curved work.
A power sander is usually unnecessary between coats. It can remove finish too fast, round crisp edges, or leave swirl marks that become obvious under the next coat. If you use one on a large, flat surface, choose a light touch and fine abrasive, keep it moving, and avoid edges. Hand sanding is slower but gives better control for most furniture and trim.
Avoid common mistakes
Do not try to sand out a run or deep brush mark with aggressive pressure across the whole surface. Level only the raised area with 220 grit on a small block, then blend the surrounding finish with 320 grit. If the defect is severe or exposes bare wood, let the surface dry fully, repair the spot, and apply another coat rather than burying it.
Do not sand through to bare wood unless you intend to restore that spot. A pale patch can show under later coats because it absorbs varnish differently. If you do break through, feather the edge with fine paper and apply varnish to the exposed area before recoating the whole piece, following the product’s instructions. On stained wood, take extra care: sanding through the finish can disturb the stain and create a light spot that is difficult to blend.
Remove dust before recoating
Vacuum the surface and nearby ledges, then wipe away remaining dust with a clean, lint-free cloth. A slightly damp cloth can work if compatible with the varnish and allowed to dry completely. Avoid a wet rag that leaves moisture in joints or grain. Tack cloths are convenient, but some contain residue that can interfere with adhesion; if you use one, choose a product intended for varnish and test it on a hidden area.
Once the surface is clean, apply the next coat as directed on the can. Keep the sanding dust out of the wet finish, and do not touch the prepared surface with bare, oily hands. If the coat still looks glossy in patches after sanding, it may be unevenly abraded; make a few gentle passes over those areas before recoating. Uniform dullness, a clean surface, and a fully cured-enough film matter more than using the finest paper available.
0 Comments