This is a table of heat conducting speeds for all the elements of Powder Toy.

Heat in powder toy uses this variable to see how often it should randomly calculate heat and apply it to nearby particles. And right now in 74.0 beta, it was also used to indicate the heat capacity of a particle, say, realistic heat.

255 is fastest, 0 is slowest. At 0 speed, heat does not conduct. At 255, it conducts instantly.