How long should I let the filler dry? If it dries too long is it harder to work with?
How fast body filler dries is determined by how much hardener is mixed in. When the correct amount is used, body filler will be sandable in about 10 minutes. If you’re filling a large spot this would be the time to use a cheese grater to knock down most of the bulk and extra filler. After about 20 – 30 minutes the filler will be completely dry and will be sandable. So once you mix the hardener in, you have to start working with it. If you take too long it will start to get sticky and difficult to spread. If you over harden the filler it will become brittle and crack easily. If you under harden, it may never harden completely and will stay tacky or moveable. A little trick to get the right amount is a golf ball sized dollop of filler to a 2 inch ribbon of hardener.
