I just finished some testing with Tri-X and HP5. After developing and washing I put the sheets, one at a time, in a tray of Photo-flo for roughly 20 seconds and then hung them to dry by their notched corners with reversed wood clothes pins. It was interesting that all the Tri-X sheets have drying marks on their bottom corners while the HP5 have no residual drying marks at all. Both films were put in the same batch of diluted Photo-flo. Any ideas? Does this mean I need to use a higher concetrate of Photo-flo with Tri-X? Also, I use distilled water when mixing my working solutions of Photo-flo.