absolutely necessary to store all papers for platinum printing
in an air-tight tin containing chloride of calcium, which must be
dried by heating from time to time. For the cold bath, however, it is
important to have moisture present during printing, or it may be after
printing and before development. If the paper is left in a dampish
room for fifteen minutes, it should be sufficient. Prints made by
exposing damp paper, or damping dry paper just before development,
must be developed within one hour if the maximum of vigor is desired;
by delaying the development some hours, the prints in the meantime
being stored in a drawer so that they may retain their moisture, an
increase of half tone and warmth of color will be obtained. If it
should be necessary to delay development for a day or two, the prints
must be dried before a fire soon after being removed from the frames,
and then stored in a calcium tube until wanted for development.

While printing, the lemon color of the paper receives a grayish
colored image, which, although faint, can, with practice, be judged as
easily as silver printing.

The developer consists of oxalate of potash and potassic
chloro-platinite--about thirty grains of the platinum salt to half an
ounce of oxalate forming about six ounces of solution; a great many
variations, however, may be made in the proportions of platinum salt
and oxalate, and different effects secured. Development is effected by
sliding the print face downward on to the developer, which must be
rocked after the development of each print to avoid scum marks. To
clear the prints they are washed in three or four baths of a weak
solution of hydrochloric acid after leaving the developer, to remove
all traces of the iron salts, and finally washed for a quarter of an
hour in three changes of water; they are then finished, and may be
dried between clean blotting paper.

Pizzighelli's process differs from the above in being one that prints
fully out in the frame without development; the paper contains the
platinum and iron salts as well as the developer, and so prints and
develops at the same time. Although excellent prints can be produced
with it, for general work the results of the paper, as at present
made, will not compare with the hot and cold bath processes. It is,
however, excellent for printing from very dense negatives, and
occasional negatives that seem extremely suitable for it. The paper
should be breathed on before print