I've just started doing gum bichromate printing and have been following gelatin and chrome alum sizing recommendations by Terry King in Coming into Focus: soak in 2% gelatin; dry; then 2 minutes in 0.5% chrome alum. The color of the alum solution seems to move from light violet to gray after soaking only a few 8x10 sheets of paper. Is this normal? Is any information available on the capacity of the alum bath?