Sealers

Sealers lock out moisture and prep surfaces for finishing. This section covers sealing untreated and painted wood, water sealers, and sealing before epoxy.

Sealing wood: seal untreated wood, seal painted wood, and seal window sills.

Water sealers: apply Thompson’s WaterSeal and Olympic vs Thompson’s.

Specialty: seal before epoxy and choosing a sealer.

For finishing after sealing, see our wood finishing guide.

How do you seal untreated wood? Clean and sand, then apply a penetrating sealer, exterior stain-sealer, or clear water repellent — two coats for outdoor use.

Do you seal wood before epoxy? Yes — a thin seal coat prevents air bubbles from outgassing into the epoxy pour.