if both silke crosses were from purebred silkies and purebred whatever you crossed them with, their trait would be something like S for silkie feathers and n for normal feathers. Breeding these two together, you would get:
S SS Sn
n Sn nn
I think. Genes are really tricky. And depending on whether the n or the S is dominant, each chick would have about a 75% chance of having silkie feathers (assuming the silkie feathers are dominant). But that doesn't mean 75% of your chicks will be sillkie-ish, just that each chick has that much of a chance. You could get all normal feathered chicks.