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How to polish gelcoat without heat or canal slurry

Updated: 23 October 2026

You have already chosen a bottle, and the risk is heat in the gelcoat, a burnt edge, or slurry in the canal. This is how to polish gelcoat once the product is in your hand: wash, work a small patch, follow that bottle's wipe rule, and keep the waste out of the water. It does not pick a brand. If the matt finish might be chalk, fade or a stain, start with [oxidised gelcoat](/hub/diy-supplies/boat-polish/sub/boat-polish-oxidised-gelcoat). Products Compared, 20 October 2026, from maker directions and UK boating guidance, not a timed test. A qualifying purchase can earn a commission at no extra cost to you. The rows are on the [boat polish comparison](/hub/diy-supplies/boat-polish).

You have already chosen a bottle, and the risk is heat in the gelcoat, a burnt edge, or slurry in the canal.

Our top picks

3M 3M Perfect-It gelcoat polish 36110

Best overall

3M 3M Perfect-It gelcoat polish 36110
9.2/10about £43.49
View offer
Gtechniq Gtechniq Marine Ceramic Top 50 ml

Rank 2

Gtechniq Gtechniq Marine Ceramic Top 50 ml
9.0/10about £79
View offer
Star brite Star brite Premium Marine Polish 500 ml

Best value

Star brite Star brite Premium Marine Polish 500 ml
8.6/10about £30.05
View offer
On this page
  1. 1.Prepare the surface
  2. 2.By hand or with a machine
  3. 3.Haze, sun, and cure
  4. 4.Waste and when to stop

Prepare the surface

Wash before you polish. Practical Boat Owner starts there, because polish on salt, diesel film or old wax loads the pad. Rinse and let the gelcoat dry. Cut a test patch about the size of a dinner plate, in daylight, not on an edge. On 3M 36110 the listing is for light oxidation. If the patch stays matt and the cloth was heavily white, you are past a light polish. Sanding a square metre at a time is PBO's route only for heavy oxidation.

By hand or with a machine

A dinghy or a small coachroof patch can be done by hand. 3M's directions put a hand section at about a 30 cm square. Work the polish until the residue has gone. Do not leave a 3M hand coat to haze. That rule is not the rule for Star brite. A machine covers flats. 3M's band for 36110 is 1,200 to 2,000 rpm, on about a 60 cm square, with a yellow wool pad. Practical Boat Owner's tip is about 1,200 rpm so the gelcoat stays cool. Keep the pad moving. If the panel is hot to the back of your hand, stop. Edges burn first because the pad digs in, so do chines by hand.
3M 3M Perfect-It gelcoat polish 36110

Testsieger

3M 3M Perfect-It gelcoat polish 36110
9.2/10about £43.49
View offer

Haze, sun, and cure

Star brite is wash, wet circles, leave it to haze, then wipe. A second coat within 30 days is on the 950 ml bullets. A UK review says not to use it in the sun. 3M's hand method is the opposite: keep working until the coat has gone. Using one rule for both liquids is how a film dries in the grain. Wax inside 3M 36110 is a one-step seal. A compound with no wax still needs a protection coat. That choice is on the ceramic coating versus wax page. Ceramic Top wants indoors at 5°C to 25°C, residue off in about one to two minutes, and off rubber and lights. Owatrol, for coloured gelcoat, stays out of direct sun.

Waste and when to stop

Slurry is the white residue on the cloth and the pad. It does not belong in the canal or the marina. The Green Blue is plain that wash-off is not automatically harmless. Bag the cloths and take them ashore. Do not rinse the pad over the side. On the Thames foreshore, the Port of London Authority expects sheeting so waste does not go into the river. This is polish residue, not antifoul sanding. Stop when the test patch does not clear, when you would need to sand a large area, or when you cannot keep the panel cool. A machine on an unknown gelcoat thickness can cut through. A hose-on sealant will not finish a chalky patch.

Common questions

Do I wash before I polish?
Yes. Wash, rinse and let the gelcoat dry before any polish goes on. Practical Boat Owner starts surface preparation there. Polish over salt or old wax loads the pad and moves the dirt. If the shine returns with a wash alone, you do not need the machine yet.
What speed is safe on gelcoat?
For 3M 36110 the directions give 1,200 to 2,000 rpm on about a 60 cm square. Practical Boat Owner's tip is about 1,200 rpm so the panel stays cool. Keep the pad moving. If the gelcoat is hot to the back of your hand, stop. Those figures are for this cutting polish, not for a wax you are wiping by hand.
Can I polish a dinghy by hand?
Yes, on a small area. 3M puts a hand section at about a 30 cm square and says to work the coat until it has gone, not to let it haze. Edges and chines are safer by hand even if you machine the flats. A whole chalky cruiser by hand is a long day, and it is still the wrong tool if the cloth comes away heavily white.
Should the polish haze, or should I work it until it is gone?
It depends on the bottle. Star brite is worked in wet circles, left to haze, then wiped, and a UK review says not to do that in the sun. 3M's hand method is the opposite: keep working until the residue has gone, and do not wait for a haze. Using one rule for both liquids is how a film dries in the grain.
Can I polish in the sun?
No for the bottles in this set that say so. 3M says not in direct sun. A UK Star brite review says the same. Heat hazes a wipe-off polish early and makes a machine pad mark the gelcoat. Move into shade or stop. Owatrol, if you are restoring coloured gelcoat, is also kept out of direct sun, between 5°C and 35°C.
Where do the cloths and slurry go on a canal?
Bag them and take them ashore. Do not rinse the pad over the side. The Green Blue treats wash-off as something you control, not as harmless water. On the Thames foreshore, Port of London Authority guidance expects sheeting so waste does not go into the river. That is polish residue, not a note about sanding antifoul.

Related pages

Boat polish buying guide

Best boat polish

Boat polish

Ceramic coating vs wax on a boat once chalk is gone

Oxidised gelcoat: chalk, fade or a waterline stain

Sources

Public UK sources and the amazon.co.uk listings compared on this page. Updated 23 October 2026.

  1. The Green Blue: Cleaning onboard (retrieved October 2026)
  2. The Green Blue: Cleaning and maintenance (retrieved October 2026)
  3. Port of London Authority: Working on the foreshore (retrieved October 2026)
  4. 3M UK: Perfect-It 36110E (retrieved October 2026)
  5. 3M technical data sheet: 36109 and 36110 (retrieved October 2026)
  6. Owatrol Direct: Gelcoat Restorer (retrieved October 2026)
  7. Gtechniq UK: Marine Ceramic Top (retrieved October 2026)
  8. Star brite: Premium Marine Polish (retrieved October 2026)
  9. Practical Boat Owner: Surface preparation (retrieved October 2026)
  10. Gtechniq: Rinse-On Ceramic (retrieved October 2026)