The NCF Hot is an extremely fast-acting accelerator. NCF Hot dramatically decreases the curing time of the glue and forces the glue to cure when it wouldn't otherwise. This accelerator is active for several minutes, so you can spray several pieces at once if you are making multiple bonds. NCF Mild and Hot are generally not suitable for use with white foam. NCF-18 is an 18oz bottle to be used refilling empty bottles.