Sand Teak Handrails Between Varnish Coats (320–600 Grit)

Teak handrails live a hard life—UV, salt, hand oils, and constant handling. A showpiece varnish job depends on what you do between coats as much as the glamour passes. The goal is simple: flatten dust nibs and brush marks, keep edges crisp, and leave a uniform micro-tooth that the next coat can grip—without blowing through at corners or polishing the film slick. This guide lays out a disciplined, hard-backed sanding routine that respects teak’s oily nature and the thin film you’re building.

Why sanding between coats matters

Fresh varnish levels as it cures, but dust and slight sags happen. A soft pad follows waves and leaves swirls that telegraph under sunlight; too-coarse paper trenches the film and risks burn-through on rails and end caps. Using a hard backing and a tight grit ladder—typically 320 → 400 → 600—cuts nibs, flattens brush marks, and sets an even scratch that promotes adhesion and consistent sheen.

Tools

• Hard sanding blocks (phenolic or hardwood with thin cork), including a narrow rail block and a small radius block for end caps
• Silicon carbide sheets: 320, 400, 600 (9×11 in); optional 220 for first leveling if the film is lumpy
• Raking light/headlamp and a soft pencil for witness marks
• Vacuum with brush tip, microfiber/tack cloths
• Solvent wipe compatible with your varnish system (e.g., mineral spirits for traditional, manufacturer’s panel wipe for 2K)
• Masking tape for adjacent gelcoat and hardware bases
• Clean, lint-free gloves; fresh, dust-free brushes or foam rollers
• PPE: respirator/dust mask, eye protection

Grit sequence

• Nib knock-down & first flatten: 320 grit on a hard block.
• Refine & align scratch: 400 grit to erase 320 lines.
• Final pre-coat tooth: 600 grit—a tight, even matte that lays down glassy next coats.

Step-by-step

1. Confirm cure and de-dust. Varnish must be hard per the tech sheet. If paper loads immediately, wait. Vacuum the rail, the surrounding deck, and your clothes; dust falls onto fresh film later.
2. Mask what you don’t want to touch. Run tape 1–2 mm shy of gelcoat seams, fittings, and nameplates. This protects adjacent surfaces during the coarse passes, then you’ll blend at the end.
3. Level nibs at 320 on a hard backer. Wrap a fresh sheet and make straight, with-the-rail strokes. Keep the block fully supported; no fingertip spot-sanding. Replace sheets early—dull paper polishes instead of cutting. For reliable, consistent stock at this opener, start with 320 Grit Sandpaper (25-pack) so you can swap the instant the cut slows.
4. Read with raking light and witness marks. Lightly pencil the length of the rail. When the marks vanish evenly, you’ve addressed that zone—stop. Sags or brush ridges? Work the whole span; don’t dig one shiny ridge or you’ll leave a flat in the profile.
5. Detail end caps and bases. Use a small radius block with 320 and take one or two passes along the curve. Corners burn through first; if you glimpse dark wood, stop and plan a spot build before continuing.
6. Refine to 400 without changing shape. Change stroke angle slightly (gentle diagonal) so leftover 320 lines stand out, then return to lengthwise strokes. Keep pressure feather-light. For longer rails or multiple pieces, keep the pace steady with 400 Grit Sandpaper (50-pack) staged at the boat so you’re never tempted to press harder on a dull sheet.
7. Blend the edges, then pull tape. With a worn 400 on a tiny hard backer, kiss right up to the tape line with two feather strokes, then remove the tape and make one more light pass to unify the sheen. This avoids a visible step under the next coat.
8. Set final tooth at 600. One or two even passes are enough—stop the instant the 400 pattern tightens into a fine, uniform matte. A fresh supply like 600 Grit Sandpaper (100-pack) ensures every sheet cuts the same from bow to stern.
9. Clean like you mean it. Vacuum with a brush tip, wipe with a barely damp microfiber, then perform your system’s solvent wipe (two-cloth method). Any residue from sunscreen, hand oils, or cleaner can cause fisheyes.
10. Re-coat within the window. Lay on a thin, even coat with a fresh brush/roller, tipping off along the rail. Watch for runs at fasteners and end caps. Maintain wet edges and proper flash—heavy coats trap solvent and print your scratch.

Special cases

Rough first coats or orange peel: If the film is lumpy after the first build coat, you can briefly open at 220 on a hard block to set flatness, then re-enter 320 → 400 → 600. Stop the instant ridges disappear; deeper scratches cost time later.
Weather windows: Varnish hates dew. If you sand late in the day, blow off dust, wipe, and coat early before the evening damp rises. If dew hits a sanded surface, re-wipe and make one light 600 pass before coating.
Oily teak trouble spots: Stubborn fisheyes? After sanding and solvent wiping, allow extra solvent flash. Some systems allow a small percentage of thinner or an anti-crater additive—follow the tech sheet.
Color touch-ups: If you spot bare wood, don’t proceed with 600. Spot-build with a couple of thin varnish dabs, cure hard, level at 320, then re-enter the sequence.

Pro tips

• Hard backing wins. Foam pads and fingertips carve flats and polish highs—exactly what you don’t want on a round rail.
• One direction per grit. 320 straight, 400 diagonal (then straight), 600 straight. Leftover lines become obvious and removable.
• Change sheets early. A loaded sheet skates and makes gloss islands that repel the next coat.
• Gloves on. Hand oils create craters. Handle parts with clean gloves from wipe through coating.
• Use a rail cradle. Support long rails so they don’t bounce under the block; bouncing makes scallops.
• Keep the dust down. Vacuum between grits and before coating; stray abrasive ruins the next coat’s look.

Aftercare

• Let coats reach full cure before hard use; fresh films imprint under dock lines and hands.
• Rinse salt regularly; salt crystals abrade the film and seed moisture.
• Wash with mild soap; avoid harsh alkalines that haze fresh varnish.
• For maintenance, scuff at 600 on the film, wipe, and add a thin refresher coat—don’t drop back into wood unless repairing damage.

FAQs

• Can I use Scotch-Brite instead of paper? Pads are convenient on inside curves, but they leave an inconsistent scratch on flats. Use hard-backed sheets on the rail’s main span; reserve pads for tight spots.
• Wet-sand or dry? Dry is cleaner on boats; if you wet-sand, use minimal water and dry thoroughly before wiping. Some systems specify dry only—follow the label.
• Is 800 better than 600? Going finer can polish the film and reduce mechanical key. 600 is the safe ceiling for most varnish systems between coats.
• What if I see through to teak? Stop. Spot-build that area, level at 320, then continue. Don’t try to “stretch” the next coat to hide a burn-through.
• How many coats? Many brightwork systems build 6–10 thin coats. Sand lightly between, then shift to maintenance coats before the film gets thin.

Video

Closing

Great brightwork is won between coats. Keep the backing hard, pressure light, and the grit ladder tight—320 → 400 → 600. Clean like a pro, coat within the window, and protect edges and end caps. Follow this routine and your teak handrails will glow with that deep, liquid look that turns heads from the dock.