Epoxy river coasters

Yes, coasters are an ideal entry into resin. They use only a small amount of resin compared with a full river table, cure faster, and the modest scale forgives the mixing and bubble mistakes everyone makes at first. You still learn all the core skills, accurate mixing, bubble control, and achieving a level glassy surface, but at a low cost and low stakes. Many people start here before attempting larger, pricier resin work.

The wood is releasing trapped air, and it was not sealed first. Porous wood holds tiny air pockets that the warmth of curing resin draws out, and they collect right where the resin meets the wood edge. Brushing a thin epoxy seal coat onto the wood and letting it cure before the main coloured pour locks that air inside, keeping the river clear. A heat gun passed over the surface also pops bubbles that do rise.

Almost always an incorrect mix ratio or under-mixing. Epoxy must be measured in the exact resin-to-hardener ratio the brand specifies, and getting it wrong leaves the resin permanently tacky or soft. Equally, it must be stirred slowly and thoroughly for several minutes, scraping the cup's sides and bottom, since unmixed resin in the corners will not cure. Measuring precisely and mixing completely, in a warm room, solves the great majority of curing failures.

Layer tones and combine pigment types. Use blues and turquoises with a touch of white for foam, going darker in the deeper resin and lighter near the surface to suggest depth. Alcohol inks spread into soft, organic, flowing patterns while mica powders stay put and add shimmer, so using both gives you movement and sparkle. Pouring in layers and letting each set slightly lets you build a convincing sense of depth rather than a flat single colour.