A retarder or inhibitor is a substance used to extend the gel time of a resin without having to shorten the curing time too much. Adding a retarder is recommended for pre-accelerated resins in warm periods. The most commonly used retardant is a 1% solution of PTBC. With an addition of 1-2% to the resin, one can approximately double or triple the gel time. An even stronger retardant is usually not desirable. for more info, see: