_Washing Collodion Process._--In "N. & Q.," No. 153., p. 320., your valued
correspondent DR. DIAMOND states "that up to the _final_ period of the
operation, no washing of the plate is requisite. It prevents, rather than
assists, the necessary chemical action.".
Now, in all other instructions I have yet seen, it is directed to wash off
the iron, or other developing solution, _prior_ to immersing in the hypo.,
and after {485} such immersion, again to wash well in water. I shall feel
greatly obliged if DR. D. will be kind enough to state whether the
first-named washing is requisite, or whether the properties of the hypo.,
or the beauty of the picture, will be in any way injured by the previous
solutions _not_ having been washed off, prior to the fixings.