toning
The process of reducing the shade (whiteness) of a
document or leaf as nearly as possible to its
original color following washing and/or
deacidification. The "toner" may he the gelatin
size itself, which will reduce whiteness to a
slight extent, or, if a greater toning effect is
required, a surface active (cationic) vegetable
dye in very dilute solution may be used. (154 , 235 )