Rule 26 of 31 · Chapter VI — Finishing and Shop Habits
Sand up through the grits
Why this rule exists
Sanding isn't one step, it's a ladder. Each grit removes the scratches left by the last coarser one and leaves finer scratches of its own. Skip a grit and the coarse scratches survive under the fine ones, invisible until finish goes on and lights them up like a road map. Climbing the grits in order, without leaps, is what turns a rough board into a surface that feels like glass and takes finish evenly. Patience here shows in every reflection.
In practice
Start only as coarse as the surface truly needs, often one-twenty for milled stock, and step up through the grades without skipping more than one at a time, one-twenty to one-fifty to one-eighty to two-twenty for most furniture. Always sand with the grain, not across it, and vacuum or wipe between grits so a stray coarse particle doesn't scratch. Before water-based coats, raise the grain with a damp wipe, let it dry, then knock the fuzz back with your final grit.
When it doesn't apply
Sanding past two-twenty or so can burnish some woods enough to resist stain, giving blotchy color, so stop earlier before staining oily or dense species. Surfaces meant for paint need less refinement. And a hand-planed or scraped surface can skip sanding entirely, since a sharp blade leaves a finish sandpaper can't match.