Re: Chrysotypes & Gold prints

John Rudiak (wizard@laplaza.taos.nm.us)
Thu, 29 Feb 1996 16:21:12 -0700 (MST)

The problem with trying to print (and not just tone) in gold salts prior
to Mike Wares development of the new Chrysotype process was the annoying
tendency of the gold to precipitate out of solution when a sensitizer was
mixed using the traditional photoreactive compounds, such as ferric
oxalate, etal. It seems that the "crux of the biscuit" (zappaism- sorry)
in this process is the introduction of a suitable ligand to hang onto the
gold and keep it in solution long enough for it to be coated and dried.
Without a more complicated description of ligand chemistry, all we need
to know is that the compound is 3,3'thiodipropionic acid, (or
3,3'thiodipropanoic aci in Britain- same stuff and that we need to use
it's disodium salt. Mike, who seems to be a fan of ammonia based systems
has chosen ferric ammonium oxalate as the light sensitive iron compound,
available here from Spectrum Chemicals. Get the ligand from Lancaster
Chemicals in NH.

The sensitizer can be compounded into three stable components which are
mixed in equal amounts just prior to coating the paper. I used to use
Gallery 100 with beatiful results until they(Rising) decided to remove
80% of the sizing last year. Haven't tried Platine yet.

Part A of the sensitizer is the gold component and is made by taking a
0.9M solution(35.4%) of gold chloride and adding to it slowly and equal
amount of 0.9M sodium hydroxide (36%)

Part B is the ligand, and is in a 1.25M strength. We want the disodium
salt, so take 100ml. water (all distilled here) and add 9.0 gm. sodium
hydroxide, COOL, and then add 20.0 gm, TDPA.

Part C is the ferric ammonium oxalate, in a 0.45M conc., which works out
to 19.3 gm in 100ml water.

These will hold up very well if kept separate, the FAO being the least
stable,

The exposure is very similar in duration and wavelength requirements to
Pt/Pd.

After exposure, develope in a 1% soln of either tartaric, citric, or
oxalic acid, or even EDTA, disodium salt. Do not reuse.

Clear a couple minutes each in 5% EDTA, Kodak Hypo Clear, and another
EDTA.Wash well

Paper choice and developer choice influence final color of the print-
haven't had time to try out all paRAMETERS.

The process is very sensitive to humidity of the coated paper, changing
the color of the prints due to the differing sizes of the deposited
colloidal gold partyicles. I have prints showing a split, with blue
highlights and burgundy shadows.

Good luck, this should get you started. I am preparing a more detailed
article on this (any interested publishers out there?) And would
appreciate hearing any other questions I might not have addressed here in
this brief.

Oh yeah, the mixed sensitizer will last about a half hour or so deoending
on conditions. I mixed 10ml, used some and came back the next morning to
a brown bottle, the inside of which was coated in pure metallic gold.

Sure hope this sends successfully, after all this typing. Its the third try.

Best

John