SANDY Hi-Build Polyester Primer is designed to eliminate the multiple steps required by 2K primers to achieve a paintable surface; it primes, fills and seals and it cures in about 45 minutes at 78 degrees. It is recommended to be sprayed over bare metal, aluminum, fiberglass and even over old paint. It fills, levels, conditions and seals becoming a tough barrier quickly eliminating bleed-through. It sands easily, either wet or dry and cures to a very tough surface for painting. No other primer is needed.