Functions of BSA and Tween 20 in western blotting - (Mar/06/2010 )

I know that BSA is used in blocking agent. However, why is it added in washing buffer ( and also primary and secondary antibodies)? What is the working mechanism of BSA?
Tween 20 is also added in the antibody, what is the function and working mechanism?
Thank you.

I use TBS-tween for my washes, you don't need the BSA. It is important in the antibody steps to reduce non-specific binding by acting as a blocker.

Detergents act as surfactants, helping coat surfaces so that the solutions cover the whole blot. They also increase the specificity of the antibody somehow - I don't know the mechanism.

Thanks!