How much epoxy resin do you need for a pour?

Measure the river channel as a box — length × average width × slab thickness — and expect big numbers: a 180 cm table with a 12 cm river and 4 cm slab is ~8.6 liters, roughly 9.5 kg of mix, poured in two or three layers. At typical casting-resin prices that’s €150-300 of material, which is why measuring twice matters. Seal the wood edges with a thin epoxy coat first, or the wood drinks resin and burps bubbles into the river for hours.

Three culprits in order of frequency: ratio error (measured by volume when the label says weight, or eyeballed), insufficient mixing (3+ minutes, scraping walls and bottom — the film on the cup wall is unmixed and ends up somewhere), and cold (below ~18 °C curing slows drastically or stalls). A surface that’s tacky but hard underneath can sometimes be rescued with a fresh correctly-mixed coat; a soft gooey mass cannot — chisel, clean with alcohol, start over.

Chemistry tuned for opposite jobs. Casting resin cures slowly (24-72 h) and cool, allowing 2-5 cm pours — it’s what rivers, molds and jewelry blocks want. Coating resin cures fast and hot in thin layers (1-3 mm), self-levels and resists yellowing — it’s for tabletop finishes and art surfaces. Pour coating resin deep and it boils; cast in thin coats and you wait days per millimeter. Check the label’s max pour depth before buying, not after.

Uncured resin and hardener are skin sensitizers: each contact raises the odds of developing a permanent allergy that ends the hobby — nitrile gloves are non-negotiable, and ventilation plus an organic-vapor mask for big pours. Never dry-sand uncured resin. Once fully cured it’s inert and food-contact safe for most quality brands (check the certification). Keep cure-stage projects away from kids and pets, and clean spills with alcohol before they harden into geology.