Make the white to black cross only if you are trying to improve whites - as John said it takes two generations. Don\'t expect to improve blacks by crossing in white. If you do a black/white cross to improve whites, try to find a black male with some silver in the hackle. That would indicate he is carrying the sex-linked dominant S gene, which would be less prone to cause brassiness in the whites than the small s (gold)gene. All female chickens are one or the other, as these are carried on the sex-link chromosome. Males can be pure for either, or have one of each. A black male with silver in the hackle will be pure for S, if he has a lemon color there he is split, and if orange or red, he is pure for s.