RiverCast

When using our casting epoxies; MirrorCast and RiverCast, it is crucial to keep it in its mold until it is fully cured (7 days). While the epoxy may seem hard after a few days, it will not reach its full strength until it has fully cured. Having the epoxy supported in the mold while it develops its full strength is important as any stress or strain put on it too early (even its own weight) can lead to warpage or sagging. Also, many casting projects will eventually be machined, the epoxy will only reach its optimal properties for machining once it is fully cured. Finally, epoxies typically shrink on the order of 2-5% by volume. Waiting until the epoxy has fully cured will ensure that the volume is stable for machining and finishing.

To be comfortable with the slow curing time of epoxy casting resins, it’s helpful to understand a little of the chemistry which controls the epoxy resin curing reaction. The reaction that hardens these resins emits no chemicals during the process. The only byproduct is heat. The larger the amount of resin and hardener that is mixed or poured, the more heat that is created during curing.

The creation of too much heat can discolor or even crack the pour as it hardens. This can ruin the final appearance of products like Mirrorcast™ and Rivercast™, which almost always makes the time, effort, and money spent on the project wasted. To avoid this situation, we’ve formulated these products to contain few or no materials which create excess heat. Unfortunately, these are the very materials that contribute to faster resin hardening.

The inconvenient consequence of this is that curing takes place slowly, often stretching into days instead of hours. But the good news is that they do cure crystal clear, very hard and tough, and with virtually no shrinkage.

For further information on epoxy curing chemistry see: Epoxy Book Section III.

MirrorCoat is a self-leveling bar and table-top coating. When using it to fill cracks and voids, it is limited in how deep you can pour the material without causing it to exotherm. The maximum depth we recommend with the MirrorCoat is 3/8" thick in room temperature conditions.

MirrorCast was designed specifically to fill medium to large sized cracks and voids, minimizing the need to pour multiple layers. Please see the MirrorCast Application Guide for detailed instructions on the application. A 'Use Chart' is also provided in the guide to help determine maximum depth pours in relation to the size of the crack or void.