Coomassie stain on Western Blots

[Martijn van Duijn]

Hi,

Just something I always wondered about.
When I transfer proteins from a gel to a (pvdf) membrane, they stick to
the membrane. In a subsequent stain, coomassie binds to the protein, and
I get nice blue bands. No problems so far.
But why don't I get a completely blue membrane after a blocking step
with a protein mix like non-fat milk? I would think that the milk
protein would both stick to the membrane, and be stained by Coomassie.

Any insights?

Thanks,

Martijn