[Breezeaway]

Breeding spotted partis, usually one piebald breed to another piebald will produce piebald. It is very hard to say though how heavy of markings you will get in a breeding as of yet. I have seen very heavily marked piebalds that have been bred together and have produced piebalds will very little spotting at all. Since each and every piebald has a unique pattern and no two are alike its very hard to guess at how the genes will come together.
There is a specific color pattern which is a little heavier than your normal piebald color of 50% white(some call Irish spotting) They are heavier on the dark color than the white.
I have not heard of any of the white faces yorkies being deaf or blind, because they do have some color on the ears or a small mark on the head somewhere.