SLOW-CURE™ 30 min. epoxy works best for forming reinforcing fillets on joints. It has the highest strength of our epoxies. It is waterproof and more heat resistant as well.. SLOW-CURE™ can be used for bonding if you’re willing to wait overnight. Fillers, such as microballoons, can be mixed with SLOW-CURE™ and FINISH-CURE™ to form a putty-like consistency. Using fillers will usually decrease the working time by about 25%. Bonded objects can be handled after 8 hours and the cured epoxy reaches full strength within 24 hours.