190Platinum Metals Rev., 2005, 49, (4), 190–195

Throughout its 166-year history, the technologyof photography has been dominated by the photo-chemistry of silver halides. Their unique highsensitivity in development provides the only viableway of capturing a negative ‘instantaneously’ in thecamera. But when it comes to printing from the‘black and white’ negative to produce a mono-chrome positive, the brevity of exposure is not animportant consideration, so the door is open tousing other, less sensitive photochemical process-es. Thus the exposure times used for printing canbe lengthy and the printing-light sources intense.Throughout the history of photography, manyalternative ‘non-silver’ printing processes havebeen devised in the quest to make images morepermanent and artistically attractive than thoseprovided by the silver media (1). Even in the dawnof photography, in 1839, Sir John Herschel stated:

‘I was on the point of abandoning the use of silver inthe enquiry altogether and having recourse to Gold orPlatina’ (2).

The pioneers of the new art-science had alreadyrecognised that platinum could be an admirableimage substance in its finely divided (nanoparticle)state. Platinum is far more inert than silver. In thepolluted atmospheres of the Victorian industrialage, silver suffered from a serious vulnerability tosulfiding, which now accounts for the faded, palebrown look of many 19th century silver pho-tographs (3).

However, it took another fifty years before aphotochemical means of printing images in ‘plat-inum black’ was perfected by William Willis (4). Itthen became the preferred medium of leading pho-tographic artists for a further three decades, untilthe Great War decreed that platinum was a strate-gic material for catalysing the manufacture of

explosives, and its frivolous use for photographyand jewellery was banned.

This put a temporary halt to the production ofcommercial platinotype paper, but Willis respond-ed by devising a palladium printing paper. Suchnoble metal processes depend on the photochem-istry of iron(III) polycarboxylates, which have alight sensitivity so low that one can only make con-tact prints from same-sized negatives, necessitatingthe use of large format cameras. Eventually, thecompetition with more sensitive silver halidepapers, produced in response to the need forenlarging miniature camera negatives, led toWillis’s Platinotype Company being wound up in1937 (5).

When image quality and archival permanenceare paramount considerations, the prime alterna-tive to silver printing still remains the platinotype,and analogous palladiotype. Since the 1970s dis-satisfaction with the commercial silver-gelatinprinting ‘monoculture’ led some photographicartists, especially in the U.S.A., to rediscover the19th century method of platinotype, and to coattheir own sensitised papers with solutions of theappropriate chemicals: iron(III) oxalate and potas-sium tetrachloroplatinate(II) (6).

The BookThe Focal Press book, “Platinum & Palladium

Printing”, Second Edition, by Dick Arentzdescribes itself as ‘the only comprehensive work’ on thissubject, and so commands our serious attention.This book is not a history (7) nor yet a chemistry(8) of the process, for which the reader must lookelsewhere. Arentz’s treatise is intended as a practi-cal manual of instruction, providing a fully detailedaccount of one method of accomplishing palladi-um-platinum prints, and of creating the large

DOI: 10.1595/147106705X70291

Photography in Platinum and PalladiumPLATINUM & PALLADIUM PRINTING, SECOND EDITION

BY DICK ARENTZ, Elsevier, Focal Press, Boston, 2005, 234 pages, 65 Duotone plates

ISBN: 0-240-80606-9 (softbound), £27.99, €40.95

An Essay Book Review by Mike Ware20 Bath Road, Buxton, Derbyshire, SK17 6HH, U.K.; E-mail: mike@mikeware.co.uk

photographic negatives that are the prerequisites.The only rival sources of published instruction inthese skills, which are admittedly briefer, can befound within multi-topic works on what has cometo be called ‘alternative’ photography (9).

Traditional Palladium-PlatinumPrinting

Arentz is the master-craftsman leading theschool of traditional palladium-platinum printingin the U.S.A. The technical content of his book isvisually leavened by duotone plates exemplifyinghis own exquisite landscape images, which wereexecuted originally in the giant format of 12” ×20”. His workroom equipment, resources, andpractices are minutely delineated in Chapter 2,‘Setting Up a Laboratory’, and provide a counsel ofperfection for all practical workers in this arena.This book will therefore appeal chiefly to advancedphotographic print-makers, especially those accus-tomed to large format practice, who are competentin the control of exposure and development toachieve precalibrated density parameters, as exem-plified by Ansel Adams’s celebrated Zone System.The sensitometry of photographic materials, mea-sured by step-tablet testing and plotting the

characteristic curves of optical density versuslog(relative exposure), is the mainstay of this work;so any readers unfamiliar with these concepts mayfind themselves a trifle challenged.

In view of the author’s concern for technicalprecision, it is a reviewer’s melancholy duty toreport some rather unfortunate errors. Chapter 3on ‘The Negative’ deals with photographic sensit-ometry, but when it comes to explaininglogarithms and their relationship to photographicstops, it makes at least five mistakes in elementarymathematics in the space of half a page: forinstance, a density of 4.0 is not equivalent to 100stops, as stated, but 13.3 stops. Likewise, thechemically-literate reader will be distressed to seein Chapter 4, on ‘Chemicals’, formulae written asK2CR7O7 (for potassium dichromate), K2C2O2 (forpotassium oxalate), and C6H5NA3 (for sodium cit-rate), among others, which are solecisms asuncomfortable to a chemist’s eye as spelling errorsto a reader, and which will not inspire confidence.

PaperWhile all the other printing parameters are con-

trollable, the paper substrate remains the last greatimponderable in hand-crafted platinum-palladium

Platinum Metals Rev., 2005, 49, (4) 191

Plate 1.1 from the Second Edition of Dick Arentz’s book “Platinum & Palladium Printing”, entitled ‘Levens, England.2000 12 × 20 inch Pd.’ The image colour, a rich yellowish-brown, is characteristic of a developed palladium print

Platinum Metals Rev., 2005, 49, (4) 192

processes, since the constituents of the sensitiserare in intimate contact with any additives in thepaper that may prove hostile and inhibiting to thechemistry. In the mid 1980s, mainly for environ-mental and conservation reasons, the methods ofindustrial paper manufacture underwent a pro-found change. However, the new papers produced– while admirable for other purposes – did not suitthe platinum printer. Chapter 5 on ‘Paper’ carriesa useful survey of tests on many commercial ‘fineart’ papers now available in the U.S.A., andreviews their suitability for palladium-platinumprinting, and how problems with them may beovercome by acidification.

In Chapter 6, ‘The First Print’, the reader willdiscover how to make a palladium print – but onlyprovided that the reader has purchased a particu-lar chemical kit (10). This is because theinstructions in this book are wedded to the prod-ucts of a particular U.S. supplier of pre-packagedchemical solutions for palladium-platinum print-ing. While this may be a convenient dependency, itmay ultimately limit the book’s usefulness.

Chapter 7, ‘Choose Your Method’, is not aswide in scope as it sounds, being solely concernedwith the method of contrast control in the print. Ifthe extensive advice about the correct making ofnegatives were to be followed in the first place,much of this Chapter would be superfluous.Chapter 8, on ‘Calibration’, provides more instruc-tion in controlling print contrast, and Chapter 9,‘The Platinum and Palladium Print’, describes themodus operandi of coating paper, exposure to ultra-violet light, and processing.

Chapter 10 on ‘Advanced Technique’ describesthe effects of humidity, variations in the develop-ing procedure, and the finishing of prints, andChapter 11, ‘Problems’, is, unsurprisingly, on trou-bleshooting.

The remaining half of the book (116 pages) isdevoted almost entirely to negatives and sensitom-etry. This is aimed at precisely matching the opticaldensity range of the negative to the logarithmicexposure range of the process. Thus Chapter 12 isabout ‘The Film and Paper Curves’, and lastlyChapter 13 is about ‘Using the Print Curves’. After

Commercial platinum print ca. 1900, by ‘C&P’, photographer unknown, entitled “Wells Cathedral, Nave lookingEast”. The image colour, neutral grey-black, is typical of a ‘cold-developed’ platinotype of the period

Platinum Metals Rev., 2005, 49, (4) 193

this are seven Appendices, mainly concerned withthe making of suitable large format camera nega-tives. The most useful inclusion here is by ‘guestauthor’ Mark I. Nelson, describing: ‘CraftingDigital Negatives for Contact Printing Platinumand Palladium’. This topic is becoming of increas-ing importance as digital imaging takes hold andfilm manufacturers withdraw their traditional sil-ver-gelatin materials from the market.

Monochrome Image ColoursThe colour of the monochrome image is an

issue of primary importance to photographicartists. It depends both on the metal and themethod. If the duotone plates of the book accu-rately reproduce Arentz’s original palladium-platinum prints, then the predominance of palladi-um in his modus operandi coupled with the use of adevelopment process would seem to result in char-acteristically yellowish-brown images. This maynot satisfy all tastes. The neutral ‘engraving’ blackso esteemed in the traditional platinum print is notseen here, nor even the rich purplish browns of‘sepia platinotype’. Indeed, it appears that theworking methods that Arentz and his suppliershave now evolved cannot readily furnish pure plat-inum prints of good quality – a failing which ispartly attributed to the constitution of moderncommercial art papers.

It is true that a fine print in palladium is mucheasier to make than one in platinum, because plat-inum(II) salts are more reluctant to be reduced toplatinum metal, which can cause poor image qual-ity, so the former is strongly recommended tonewcomers in this field (10). Indeed, some readersmay recognise the origin of this problem: that thechemical kinetics of complexes of a 3rd row tran-sition metal like Pt are generally slower than thoseof a 2nd row metal like Pd, due to larger crystalfield activation energies, resulting from the spatialextent of the d-orbitals. Thus the more labile Pd(II)complexes are easily reduced to the metal byFe(II).

It is regrettable – and some readers of thisJournal may think it unprofessional – that this cur-rent practice should be referred to by many as‘platinum printing’, when the product usually

chiefly consists of palladium. In comparing the useof these two noble metals for photography, thereare also the considerations of cost and safety.Palladium is usually much less expensive than plat-inum, but readers will know that there have beensome wild market price excursions in the past (dueto speculation) which have sent shock wavesthrough the printing community.

A health and safety view of the metal salts,omitted from Arentz’s book, is that chloro-com-plexes of platinum(II), unlike those ofpalladium(II), have a marked biological activity,and constitute a human allergenic hazard. This wasfirst discovered in 1911 through cases of industrialillness arising among workers in an early platino-type paper factory.

Indeed, while the illustrations in both editionsof Arentz’s books indicate that very fine palladi-um-platinum prints may be made by the hands ofa master who is prepared to take limitless technicalpains, the reader may wonder if this is the onlypossible route to success. The second edition nowomits any account of an alternative method whichhe briefly described in his first edition, namely, amodern ‘print-out’ method of platinum-palladiumprinting, employing a slightly different photo-chemistry. It seems fair to redress this imbalanceby comparing the two below.

Development Printing versus thePrint-out Process

The ills of the traditional method stem from thechosen photosensitive iron(III) salt: ferric oxalate.This is a notoriously wayward and ill-characterisedsubstance; the nature of the product, which is evi-dently capable of extensive polymorphism, varieswith its method of preparation. An indication ofthe difficulty of manufacture is apparent from itscommercial price: iron(III) oxalate costs over 100times as much as iron(II) oxalate! It is obtained asan amorphous solid, seemingly not crystallisable,and in consequence its structure has not beendetermined by X-ray diffraction. It is hard to dis-solve in water without an additional ligand, and theaqueous solution undergoes changes in its proper-ties over time, to the extent that scrupulousworkers (as we learn from Arentz’s Appendix G)

Platinum Metals Rev., 2005, 49, (4) 194

prefer to make up a fresh solution each nightbefore printing.

The photochemistry of iron(III) oxalate may berepresented approximately thus:

hνFe2(C2O4)3 ⎯→ 2FeC2O4↓ + 2CO2↑

The photoproduct, iron(II) oxalate, is highly insoluble and cannot reduce platinum(II) or palla-dium(II) salts to metal, unless it is solubilised bycomplexation, for example, with oxalate ions:

[PtCl4]2– + 2FeC2O4 + 4C2O42– →

Pt↓ + 4Cl– + 2[Fe(C2O4)3]3–

Hence the traditional ‘development’ process ofplatinum and palladium printing, which calls for aprocessing bath of hot potassium oxalate solution,or similar ligand, to bring out the metal image inthe exposed paper.

However, there is an accessible alternative forthe light-sensitive ingredient: ammonium iron(III)oxalate. This is a well-characterised, highly crys-talline, analytically pure substance, of knownmolecular structure. It is universally available atlow cost, and dissolves very readily to give a stableaqueous solution. Moreover, its photochemistryleads to a ‘print-out’ process, as follows:

hν[Fe(C2O4)3]3– ⎯→ [Fe(C2O4)2]2– + 2CO2↑

The iron(II) photoproduct in this case is already asoluble complex, so if the sensitised paper con-tains sufficient water molecules, as will be the casefor any cellulose paper exposed to ambient relativehumidity of 70- 80%, the ions can mobilise imme-diately to reduce the platinum metal in situ:

[PtCl4]2- + 2[Fe(C2O4)2]2- ⎯→Pt↓ + 4Cl- + 2[Fe(C2O4)2]-

Thus a ‘print-out’ process results, in which thefinal image is formed substantially during the lightexposure, and no ‘development’ bath is required,simply ‘clearing’ baths to remove the excess solu-ble chemicals. This enables a modus operandi quitedifferent from the traditional method, and moreeconomical in time, effort, and materials. Imagesmay be printed satisfactorily ‘by inspection’, with-out prior calibration (11). The print-out process is‘self-masking’, in that the blackening of the shad-

ow tones inhibits their further darkening by light,so a long density range in the negative may beaccommodated, and the control of contrast ismore relaxed. By regulating the relative humidityof the paper before exposure, better image coloursresult with palladium, because the metal nanopar-ticles are allowed to grow larger, and can furnisheven a neutral black. Provided that a suitable papersubstrate is chosen, the method can also yield anexcellent print in pure platinum.

In conclusion, it might be observed that, formany artists, the intrusion of technical minutiaeinto the creative workflow can tend to inhibit theirendeavours. If the science can be predesigned towork as transparently and unobtrusively as possi-ble, so much the better for art.

Artists deserve the best science.

References1 M. J. Ware, ‘Noble Metals for Common Images’, in

“Photochemistry and Polymeric Systems”, eds. J. M.Kelly, C. B. McArdle and M. J. de F. Maunder,Special Publication No. 125, Royal Society ofChemistry, Cambridge, 1993, pp. 250-265;http://www.mikeware.co.uk/mikeware/Ironic_Manifesto.html

2 L. J. Schaaf, “Out of the Shadows: Herschel, Talbotand the Invention of Photography”, Yale UniversityPress, New Haven & London, 1992

3 M. Ware, “Mechanisms of Image Deterioration inEarly Photographs: The Sensitivity to Light of W.H. F. Talbot’s Halide-Fixed Images 1834-1844”,Science Museum and National Museum ofPhotography, Film & Television, London, 1994

4 M. Ware, ‘The Eighth Metal: the Rise of thePlatinotype process’, in “Photography 1900”, eds. J.Lawson, R. MacKenzie and A. D. Morrison-Low,National Museums of Scotland, Edinburgh, 1994,pp. 98-111; http://www.mikeware.co.uk/mike-ware/Eighth_Metal.html

5 For the early history of platinotype, readers arereferred to: I. E. Cottington, ‘Platinum and EarlyPhotography’, Platinum Metals Rev., 1984, 28, (4),178; see also: D. E. Webster, ‘Noble Metals inPhotography’, Platinum Metals Rev., 1987, 31, (3), 124

6 G. Tice, ‘Durable Beauty in Images of Platinum’, in“Caring for Photographs”, Life Library ofPhotography, Time-Life Books, Alexandria,Virginia, 1972, pp. 86–93

7 L. Nadeau, “History and Practice of PlatinumPrinting”, Atelier Luis Nadeau, New Brunswick,Canada, 1994

8 M. J. Ware, ‘An Investigation of Platinum andPalladium Printing’, J. Photogr. Sci., 1986, 34, 165;http://www.mikeware.co.uk/downloads/Palladium_Printing.doc

Platinum Metals Rev., 2005, 49, (4) 195

9 R. Farber, “Historic Photographic Processes”,Allworth Press, New York, 1998; C. James, “TheBook of Alternative Photographic Processes”,Delmar, Thomson Learning, New York, 2002

10 Maker/Supplier: Bostick & Sullivan, Santa Fe, NewMexico, U.S.A., http://www.bostick-sullivan.com/;Supplier: Photographers’ Formulary, Inc, Condon,Montana, U.S.A., http://www.photoformulary.com/

11 M. Ware, ‘Platinum Reprinted’, Br. J. Photogr., 1986,133, (41), 1165; M. Ware, Br. J. Photogr., 1986, 133,(42), 1190; P. Malde, ‘New Solutions for PlatinumPrinters’, View Camera, September/October, 1994,36-41;http://www.mikeware.co.uk/mikeware/Platino-Palladiotype.html

The Reviewer

Dr Michael J. Ware is a chemist with a D.Phil. in spectroscopic researchfrom the University of Oxford. Following an academic career at theUniversity of Manchester, (Honorary Fellow), he now independentlystudies the history, science, art and conservation of ‘alternative’photographic processes. His work on printing in noble metals, especiallygold, platinum and palladium, was awarded the Hood Medal of the RoyalPhotographic Society. He is a consultant to the National Museum ofPhotography, Film and Television, and has supervised postgraduateresearch in photograph conservation at the Victoria & Albert Museumand the Royal College of Art, and in alternative photographic processesat the University of Derby. He exhibits his own photographic work widely,and conducts workshops in the U.K. and U.S.A. His research ispublished in popular and academic scientific and photographic literature,such as History of Photography. He has published books on Talbot’sphotogenic drawing process (1994) and Herschel’s cyanotype process(1999). His books on Herschel’s chrysotype – photography in gold – aredue out shortly.His website is: http://www.mikeware.co.uk/