how long until generally considered pure bred?

[elsiehammer]

My winter grouping is all the hens (99% large breed) together, with my silkie rooster. My niece has all of her chickens mixed also, with several roosters. We each now have the same burning question (haha). After we put the roosters with their matching hens in separate facilities, how long before we can expect the eggs produced in each cage to be pure bred? I did have a half silkie last year, and though it was tasty, I'd like to be quite sure my full size rooster is the papa for the full sized hens. My niece has several nice trios, the eggs of which she'd like to be pure.
Anyone know a safe amount of time?
Thanks

 

[Katy]

About 4 weeks.

 

[kid-n-chickens]

The resource I just read for State Poultry days says that sperm can live for 4weeks, so I would say collect at day one of the 5th week and you should be all clear.