Ranthane Catalyst High Temp Coating (AU-CAT-2X1) by Randolph is hydroscopic (sensitive to moisture) and will immediately start to polymerize in the presence of moisture. Therefore, it is very important the catalyst container cap be tight in strorage. Use only with Ranthane HS Colored Polyurethane. Two part Ranthane HS Polyurethane to one part Catalyst. For Aerospace Use Only. Warning: Flammable