What would be the best "release agent" to apply to a fiberglass mold, before pouring a concrete cast?
2) What would be the best "release agent" to apply to a fiberglass mold, before pouring a concrete cast? I made the fiberglass mold from an 18 X 18 inch architectural concrete, column pier cap. I applied 3 coats of paste wax to the pier cap before applying the fiberglass resin and the mold turned out pretty good. I would wing it and again use paste wax, but I don't want to run the risk of any of the wax coming loose into the wet concrete, as I press down on the concrete mix as it is setting, to bring up air bubbles, etc. I did notice that when I removed the fiberglass mold from the pier cap, almost all the paste wax came up off the concrete and stuck to the fiberglass. Should I just use paste wax inside the mold? I am planning on inserting a couple pieces of wire meshing and tying bailing wire around the webbing, out and up, so I have something to pull the casting (heavy. 60 lbs?) up with.
2) My second question is about these air bubbles. The mold came out perfectly smooth, from a perfect original. I'm using QuiKrete that I got at home depot. The aggregate contains only very small pebbles, no large stones. The mold is about 4 inches high. My thought would be to use a looser mix, yet I don't want to be too loose to sacrifice strength.
What would be the best method to insure there are next to no air bubbles on the surface of the finished cast?
Advice and suggestions would be very welcomed here. Thank you!