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Re: Re: packham platinotype toning method
A little more info, from The Complete Photographer:
A curious method of toning platinum prints is due to Mr. J. Packham. If a
finished and washed platinotype is immersed in a solution of the vegetable
dye, catechu, the paper is not dyed, but the image gradually becomes brown.
It was subsequently shown by Mr. Chapman Jones that the action depends on
slight traces of the iron salt still remaining in the image after all the
acid washings to get rid of it, and not on any action between the dye and
the platinum itself. This is immaterial to the user of the process, and the
method gives a fairly permanent result. Catechu, or cutch, is the dye used
for ships' sails, and gives them that rich brown colour which is so
effective pictorially. Incidentally it helps to preserve the sail. Two drams
of dyer's catechu or cutch in powder is boiled in 5 ozs. of water for five
minutes, allowed to cool, and has added to it 1 oz. of alcohol. This forms
the stock solution, and keeps indefinitely. Half a dram of this liquid is
added to a pint of water, the solution is heated to 130 to 150 Fahr., and
the print is immersed. Toning starts at once, and can be stopped at any
moment that seems desirable, the operation having gone as far as it will go
in about ten minutes, Toning may be done with a cold solution, but this
takes much longer, up to four and twenty hours.