Surfacing Wax

SKU:SM-SWAX02

$4.55 USD

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105 in stock

Size: 2oz

2oz Pint Quart Gallon 5 Gallon

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Unwaxed polyester and gelcoat stay tacky in air because the styrene at the surface never fully cures. Surfacing wax is the fix: stir it into the final coat only, and it floats to the surface, seals the film off from oxygen and lets that last layer cure hard enough to sand and polish.

Add 1/2 oz per quart, or 2 oz per gallon (about 20 drops per ounce)
Final coat only, never in laminating layers you plan to bond to
Still needs MEKP; wax is an additive, not a catalyst
For unwaxed polyester resin and unwaxed gelcoat
Sizes: 2 oz, pint, quart, gallon, 5 gallon

If you have to recoat over a waxed layer, sand it and wipe with acetone first. The wax film that made the surface cure is the same film that will keep the next coat from sticking.

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Technical Specifications

Mix 1/2 oz per quart (2 oz/gal, 20 drops/oz) into the final coat only

Resin TypeWax additive (sanding aid) for polyester resin & gelcoat

Mix Ratio1/2 oz per quart (2 oz/gal, 20 drops/oz) into the final coat only

CatalystMEKP still required - wax is an additive, not a catalyst

Apply OverFinal layer only; sand + acetone-wipe the wax film before any recoat

Best ForTack-free, sandable final coats on unwaxed resin/gelcoat

Do I need to add wax to gelcoat?

Only if you are using unwaxed (sanding) gelcoat. Unwaxed gelcoat stays tacky on the surface because air stops polyester from curing, so you add surfacing wax to the final coat, or spray PVA over it, to seal out air and cure it hard for sanding. Our Finish Kits ship the wax as a separate bottle with the gelcoat: lay your build coats unwaxed so they recoat without sanding, then stir 1/2 to 1 oz of wax per quart into the last coat only.

What's the difference between waxed and unwaxed gelcoat?

Waxed gelcoat has an additive that rises to the surface as it cures, sealing out air so the coat hardens tack-free and is ready to sand. Unwaxed (sanding) gelcoat has no additive, so it stays tacky until you add surfacing wax to the final coat or cover it with PVA. Use unwaxed when you plan to lay more coats, and use waxed for the last coat.

Why is my gelcoat still tacky and not curing?

A tacky surface almost always means air-inhibited cure, not too little catalyst. Unwaxed gelcoat will not harden on top until you add surfacing wax to the final coat or seal it with PVA. Other causes are too little MEKP, temperatures below about 60°F, or high humidity. Confirm your catalyst ratio, warm the shop, and wax or PVA the last coat.