How much epoxy you need
Epoxy is sold by volume or by weight, and running out in the middle of a pour can ruin a project. The calculation is simple: the volume of the space you fill, plus a margin for waste.
The formula
Volume = length × width × depth × number of pieces × (1 + waste)
Weight = volume × density, about 1.1 kg per liter (9.2 lb per US gallon) for most mixed epoxies.
Worked example
A tabletop 48 × 24 inches with a 1/8 inch flood coat and 10% waste:
- Volume: 48 × 24 × 0.125 = 144 cubic inches ≈ 2.36 L.
- With waste: 2.36 × 1.10 ≈ 2.60 L, or about 88 fl oz (0.69 gal).
- Weight: 2.60 × 1.1 ≈ 2.86 kg, about 6.3 lb.
- At a 1:1 ratio: 1.30 L of resin and 1.30 L of hardener.
River tables and deep pours
For a river table, measure the gap between the slabs: average width × length × thickness. Live edges are irregular, so take several width measurements and use the average. Add 10 to 15% for the resin that soaks into the wood and leaks through the mold. Seal the wood with a thin coat first to limit air bubbles.
Mixing ratios
| Ratio | Resin share | Hardener share |
|---|---|---|
| 1 : 1 | 50% | 50% |
| 2 : 1 | 67% | 33% |
| 3 : 1 | 75% | 25% |
Some brands give the ratio by weight instead of by volume; they are not the same because resin and hardener have different densities. Follow the label exactly: an off-ratio mix may never fully cure.
Pour depth
- Coating resins: about 1/8 inch per coat. Thicker coats can overheat, yellow or crack.
- Deep pour resins: 1 to 2 inches or more per pour, with a long cure time.
Respect the maximum depth on the data sheet. Pour in layers when needed, waiting for each one to reach the recommended stage.
Tips
- Work at 70 to 80 °F (21 to 27 °C); cold resin is thick and traps bubbles.
- Mix slowly for the full time on the label, scraping the sides and bottom of the cup.
- Wear nitrile gloves and work in a ventilated space; uncured epoxy can cause skin sensitization.