System Three Resins manufactures two epoxy casting resins for woodworking applications: MirrorCast and RiverCast. They each have a specific niche in where they perform best.
MirrorCast is formulated with a hardener that is more reactive than the RiverCast. Because of this, it’s fine-tuned for small to medium size voids, such as knots, checks, and cracks in wood slabs. Though it can be used for river tables, it's not ideally suited for this application. In most river table scenarios, the MirrorCast will require 2-4 pours to reach a 1.5” depth. MirrorCast is a great choice as an all-around epoxy for the workshop. It produces crystal clear results for the most common void filling applications.
RiverCast's hardener has a lower reactivity than the MirrorCast and consequently has a much slower rate of cure. The low reactivity allows RiverCast to be poured into large areas up to 1.5” deep without the worry of creating too much heat and discoloration. It produces super clear casts in large volume pours such as river tables and large inclusions in wood substrates. Because of its super slow cure speed, it’s not ideal for small knots and cracks. Though it will cure hard, it will take an extended period of time to do so.