Purchase from Sigma, purified casein powder.  There may be other sources
Dulbeccos PBS is available from Sigma in large volume, powder form also.
Cat #D5652.

Tacha method  5 gm in Dulbeccos PBS (any PBS probably will work)
	      0.5 g thimerosal
	      in 1 liter DPBS
              Stir overnight, adjust pH to 7.4, store at 4C.

Reference:  Tacha DE, et al  Casein reduces nonspecific background
             staining in immunolabeling techiques  J Histotechnology
             15:137-132, June 1992



Gayle Callis