He said that failures were normally
the result of one of three causes:
1. The character of the light.
with ruby and other safelights, and as a result of these experiments
recommended Forrest's non-actinic orange, plus one thickness of orange
tissue paper. This, he claimed gave absolute freedom from fog, even
with bright sunlight passing through it.
2. Want of patience in preparing the
placing the bottle containing the solution of the gelatine pellicle should
be placed in a hot bath, and giving frequent stirrings with a glass rod
until no soft substance could be detected at the bottom of the bottle.
Only then should the solution be passed through a fine linen to remove
3. The length of time allowed for
the plates to dry spontaneously.
Palmer commented that
too long protraction of the drying process could result in blistering at
the centre of the plate and frilling at the margin of the plate. He,
and others, had devised apparatus to ensure that the plates could be
placed on a level surface and a steady flow of warm dry air passed over