Camera Work: A Photographic Quarterly (1905 (Heft 11))

Black spots may be caused by dust or foreign matter getting between the
plaster and the print, or defects in the paper or plaster. The point of a
penknife is the best remedy.
A picture from an overexposed initial print looks like all over-
exposures do—no depth in the shadows and no high lights. A picture upon
an insufficiently washed initial print looks very much like an overexposure,
with the exception that in the case of a properly washed and overexposed
print the margin covered by the rebate of the printing-frame will be quite
white, whereas in an underwashed print the margins will be covered with
insoluble pigment.
Try and avoid overexposure; a print which looks underexposed may
not be so in reality, and if the contact with the plaster is prolonged to about
one hour, it will in all probability turn out a good picture.
I can not at the moment recall any further difficulty that the beginner
might encounter. As Baron von Hübl remarked in his treatise on ozotype,
“the process presents no difficulty to an intelligent worker, and will, when
a few initial imperfections have been overcome, develop into a much-used
printing process.” The imperfections associated with all new work have now
been overcome, and a beautiful, simple, and permanent printing process is
ready for the earnest picture-maker. Thomas Manly.