How to seal wood before an epoxy pour

Wood is full of air. When resin surrounds it, that air leaves, and it leaves through your pour. A seal coat is a thin layer of epoxy applied first to close the surface. Many manufacturers in our database ask for one, and several say what to seal with and how long to wait.

Why seal at all

EcoPoxy recommends seal-coating any surface that will be submerged in its casting resin, because air and moisture migrating out of the material cause bubbles (EcoPoxy). TotalBoat describes the seal coat as an airtight barrier between porous wood and the flood coats that prevents bubbles, pinholes and surface defects (TotalBoat). MAS goes further for its original Deep Pour: its data bulletin says not to pour it onto unsealed wood or porous surfaces at all (MAS Epoxies).

Do not seal with a slow deep-pour resin

A seal coat should cure reasonably fast so you can move on. Several deep-pour data sheets say their own product is the wrong tool:

TotalBoat’s Fathom data sheet says Fathom cures too slowly to be used as the seal coat (TotalBoat Fathom TDS). TotalBoat’s river table guide pairs Fathom with a different epoxy for sealing, and notes that ThickSet can serve as both seal coat and pour (TotalBoat).
MAS does not recommend Deep Pour X as a seal coat, because the seal would need two or more days before sanding (MAS Epoxies).
EcoPoxy names UVPoxy, its faster coating resin, as the preferred seal-coat product (EcoPoxy).

The general pattern: seal with the manufacturer’s coating or table-top epoxy, then pour with its deep-pour epoxy. Mixing brands is possible, but then you are outside the pairings the manufacturers describe.

How thick, and how much resin

A seal coat is thin. TotalBoat applies a 1/16 in layer spread with a spreader, making sure it covers every crack and void (TotalBoat). Stone Coat suggests about 1 oz of mixed epoxy per square foot for a seal coat on porous surfaces such as live-edge wood (Stone Coat Countertop Epoxy TDS). EcoPoxy notes that particularly porous pieces may need two or three seal coats (EcoPoxy UVPoxy guide).

To size it, add up the area of every surface the pour will touch (live edges, the undersides that will be submerged, the form-facing ends) and use the flood coat calculator with a 1/16 in (1.6 mm) coat. For a river table, remember both live edges run the full length of the slab and are as tall as the pour.

Timing the next step

Manufacturers disagree on whether the seal coat should be tacky or fully cured when the main pour goes on, so follow the one for your product:

Product	Seal coat, then…	Source
Superclear Liquid Glass Deep Pour	Pour while the seal coat is tacky	Instructions
Promise Fast Cure Deep Pour	Pour 3 hours after the last seal coat	TDS
MAS Table Top Pro	Let the seal coat cure rock-hard, sand with 80–120 grit, then flood coat	Instructions
UltraClear Deep Pour	2–3 coats of UltraClear’s bar-top epoxy, sanding lightly between coats	Instructions

EcoPoxy adds that cured seal coats should be abraded and cleaned before the pour (EcoPoxy).

Step by step

Sand and clean the wood. Remove loose bark and dust.
Mix a small batch of the coating epoxy your manufacturer names for sealing.
Brush or spread a thin coat over every surface the pour will touch, working it into cracks and voids.
Add a second or third coat on very porous wood.
Wait for the state your pour product asks for (tacky, or cured and sanded), then pour.

Common mistakes

Sealing with the deep-pour resin when its data sheet says not to.
Skipping the undersides and ends. Air escapes from any wood surface in contact with the resin.
Letting the seal coat go too long when the pour product wants it tacky, or pouring too soon when it wants it sanded.