Practical Printing with Colloidal Gold
by Tony McLean
3,3 Thiodipropionic acid. C6H10O4S (M.W. 178.20) This is the compound, which is at the heart of this process. It is a fine white powder and is available in this country from Sigma Aldrich at approx. £8 for 100 g and from Lancaster chemicals, New Hampshire in the States. Again, they seem to have a minimum order of $50. There seems to be little safety information available on this product but normal precautions in the handling of chemicals should be adhered to. Quoting from the Journal of Photographic Science, Vol. 42, number 5, (1994), pp 157-161, "Photographic Printing in Colloidal Gold" by Dr. Mike Ware: "Warning: in any experimental exploration of the chemistry of this process, it would be prudent to avoid two hazards: the precipitation of the dangerously sensitive explosive, fulminating gold, which results when ammonia is added to gold (III) complexes, and the possible formation of the unpleasant vesicant, mustard gas, S(CH2CH2CL)2 by inadvertent chlorination of the ligand".
Ammonium ferric oxalate. This is the green crystalline light sensitive compound used in both the Ware and Ziatype versions of the “printing out “platinum palladium process. It is available here from Silverprint in London at £3.00 for 25 g. It is also sold by Bostick & Sullivan in the States. The developers: e.d.t.a.-di sodium, tartaric acid, citric acid, and oxalic acid. These developers are also available from the suppliers named above. Citric acid and tartaric acid can also be purchased locally from home wine making shops and some chemists. Papers. I have limited my exploration of this process to three papers from the Arches stable: Arches Platine, Bergger COT 320 and Arches Aquarelle. The first two papers are starch sized and the latter; Aquarelle is sized with gelatine. These papers are all of approximately the same weight i.e. 300g/m2 and have excellent wet strength. Their sizing is of a sufficient hardness to allow the sensitiser to be spread evenly. A quick test with another paper, Whatman H.P. (a soft sized paper) revealed that this paper was insufficiently sized for this process and it soaked up the sensitiser like blotting paper. Chrysotype sensitiser is far less viscous than the traditional Pt/Pd sensitisers.
I am indebted to the late John Rudiak of New Mexico who was tragically in 2000 whilst riding his new motor bike. His interpretation of Dr. Mike Ware’s New Chrysotype process in March of 1996, revealed to the “Alt. Process” community his adaptation of Dr. Ware’s scientific paper, which was previously published in the Journal of Photographic Science, Vol. 42 (1994). John put it into words and numbers, an account that would be understandable to non-chemists such as myself. I quote below from John Rudiak’s original E-Mail:
“The problem with trying to print (and not just tone) in gold salts prior to Mike Ware’s development of the new Chrysotype process was the annoying tendency of the gold to precipitate out of solution when a sensitiser was mixed using the traditional photo reactive 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 acid in Britain) - same stuff and that we need to use it's di-sodium 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 sensitiser can be compounded into three stable components, which are mixed in equal amounts just prior to coating the paper. Part A of the sensitiser 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 (3.6%) Part B is the ligand, and is in a 1.25M strength. We want the di-sodium 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 ammonium ferric 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, develop in a 1% soln. of either tartaric, citric, or oxalic acid, or even EDTA, di-sodium salt. Do not reuse. Clear for a couple minutes each in 5% EDTA, Kodak Hypo Clear, and another EDTA. Wash well. Both the paper and developer choice influence final colour 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 colour of the prints due to the differing sizes of the deposited colloidal gold particles. I have prints showing a split, with blue highlights and burgundy shadows.”
I have taken the liberty of simplifying John’s instructions even further to give the reader more manageable quantities of the three constituents suitable for an exploration of the Chrysotype
process. Note: All water to be distilled. If you are of a nervous disposition, or do not possess the necessary skills or equipment to make up these solutions, then I would advise you to make
contact with the chemistry department of your local college. The promise of an original print will usually be enough to persuade a technician to prepare this chemistry for you.
Copyright 2001 by Tony McLean.