Surface Prep: Planing, Scraping, Sanding

Planing

The best surface for most finishes comes straight off a sharp, finely set smoothing plane. The blade severs the fibers cleanly, leaving a surface that’s flat, crisp, and clear, without the fine scratches and packed dust of sanding. Pre-industrial furniture was finished from the plane and scraper, and its subtle tool marks are part of its look ¹.

For a finish-ready planed surface:

• Hone the smoother just before final passes.
• Set it for the finest shaving that cuts full width.
• Set the cap iron close and the mouth tight.
• Plane with the grain, overlapping passes.
• Ease arrises (sharp edges) with a block plane or a few strokes of fine sandpaper.

Scraping

A card scraper - a thin rectangle of steel - takes gossamer shavings with a tiny hook turned on its edge. It’s the cure for tearout in figured or reversing grain, where every plane direction tears, and for leveling small areas.

Sharpening (see the video):

1. Joint the edge square with a mill file.
2. Hone the edge and faces on a stone to remove file marks.
3. Burnish: draw a hardened burnisher along each face, then along the edge at a slight angle, to turn a small hook.

To use it, hold it with both hands, flex it slightly with your thumbs, tilt it forward, and push (or pull). A sharp scraper makes shavings, not dust. Cabinet scrapers hold the blade in a frame for larger surfaces.

Sanding

Sanding is the most common prep and the least pleasant. Rules:

• Start with the coarsest grit needed to remove defects and machine marks - often 120 on planed wood, 80 or 100 on rough or machine-planed boards.
• Don’t skip grits: each one should just remove the scratches of the last. Skipping leaves deeper scratches that the finer grit can’t reach and that show under finish ².
• Stop at the right grit for the finish: typically 150 to 180 under a film finish or paint, and 180 to 220 under oil; very fine sanding can keep stain from penetrating evenly ².
• Sand with the grain for the final grit; cross-grain scratches stand out.
• Use a block on flat surfaces; fingers sand hollows.
• Clean between grits (vacuum or a brush) so loose coarse grit doesn’t scratch at the next stage.
• Wear a respirator: sanding makes the most hazardous fine dust in the shop (see Dust Collection).

Raise the grain before a water-based finish or dye: wipe with a damp cloth, let dry, and lightly sand off the raised fibers with the final grit.

Inspect before finishing

Turn off overhead lights and shine a light low across the surface (raking light). Look for:

• Plane tracks and ridges.
• Tearout and fuzzy grain.
• Sanding swirls and cross-grain scratches.
• Dried glue, which repels stain and finish (a wipe with mineral spirits makes it show).
• Dents (steam them out with a damp cloth and a hot iron).

Fix them now; finish will only magnify them.

What to take from this

Smooth with a sharp, finely set plane where you can, and scrape tearout with a burnished card scraper. When sanding, start only as coarse as needed, step through every grit, finish with the grain, and stop around 150-180 for film finishes or 180-220 for oil. Raise the grain before water-based finishes, and inspect in raking light for glue, swirls, and tearout before the first coat.