Additives for extinguishers have to provide stable and powerful solutions applied to all the different nozzles - spraying and foam. To achieve the A efficiency (solids) those solutions need to have a great wetting power (both in surface and below) and avoiding the ember to get in fire again (fireproofing power). To achieve the B efficiency, the foam has to be fluid in order to get a good control of the fire as well as finishing all the small latent fires off.