Note 9 — Chapter III
S. R. (Sylvester Rosa) Koehler translation
(p. 25.) I have never been able to notice this turning dark of the lines, although I have had plates in the bath for several hours, and some of my artist acquaintances whom I have consulted on the point, have confirmed my experience. Possibly the phenomenon described by M. Lalanne may be caused by impurities in the acid.