This is a copy of an article published by Paul L. Anderson in American Photography in October 1937. It gives a fairly good overview ‘state of the art’ platinum printing back in the 1937. He wrote a second article the following year, Hand-Sensitized Palladium Paper, which describes some of the differences between the two metals.

Hand-Sensitized Platinum Paper

Paul L. Anderson, American Photography, October 1937

So many inquiries have been received as to the use of platinum paper, and this proof of reviving interest in one of the finer printing mediums is so encouraging to those of us who have the welfare of pictorial photography at heart, that I find great satisfaction in acceding to the request of the editor of this magazine for an article on the subject.

It is in one way unfortunate that the enthusiasm for high-speed production has popularized bromide and chloride papers to such an extent that the manufacture of platinum paper in this country has been abandoned, though it can still be got from The Platinotype Company, 60 High Street, Penge, London S. E. 20, England. But from another point of view it is not entirely regrettable, since the beauty of the hand-sensitized paper exceeds that of the commercial article by as much as commercial platinum surpasses the esthetic quality of chloride or bromide paper; the hand-made product is almost always to be preferred for pictorial work.

There are five printing mediums which to the pictorial worker show prime excellence; platinum, carbon (and to a lesser extent its cognate, carbro), gum, Fresson, and bromoil. I have not attempted to rate them in order of merit; indeed, it would be impossible to do so, for although it is difficult to convince an enthusiast in any of these mediums that there is any merit whatever in the other four, the fact is that each will do certain things that none of the others can accomplish. It is not my intention to discuss the characteristics of all five of these mediums, but let us consider the advantages and the disadvantages of hand-sensitized platinum paper.

Disadvantages.—(1) It is a contact medium. Enlargements have, it is true, been made on platinum paper, but only in limited sizes and with very special apparatus; in general, the negative must be the same size as the finished print.

(2) A strong light is needed for printing. I have made small prints from thin negatives by a 500-watt Mazda, but as a rule one must use daylight, a carbon arc, or a mercury vapor lamp.

(3) It is almost impossible to alter the internal relationship of values while processing. Of course one can always sun down or hold back certain areas, as in any form of printing or enlarging, but one cannot emphasize the lights with a brush, as in carbon, Fresson, or gum, nor can weight be added to chosen areas at will, as in bromoil. It is true that some workers have devised a scheme for brush-developing platinum, but the results are not usually very satisfactory; they are apt to look more like wash drawings than like photographs.

(4) The color possibilities are limited. Instead of the nine or ten colors available in Fresson, the thirty or more supplied in carbon, and the infinite number possible in gum and bromoil, one is restricted to cold, neutral, and warm black, and browns ranging from brown-black to sepia. It is true that other colors may be obtained by subsequent toning with various salts of iron, copper, and uranium, but some of these colors are certainly fugitive, and they are at best of doubtful permanence.

Advantages.—Permanence. If a good linen stock is used, and the prints are properly cleared and washed, the results are as stable as any oil painting or charcoal drawing – and there are in existence charcoal drawings known to be fifty thousand years old, which would seem as long as any photograph deserves to live.

(2) Modifications of total contrast are very easily made. It is supremely easy to get a strong print from a weak negative, or vice versa.

(3) Simplicity. The coating, printing, developing, and clearing of platinum paper demand far less labor and far less technical skill than does any other printing medium except blueprint; it is vastly easier to make a good hand-sensitized platinum print than it is to make a good bromide enlargement or gas-light print.

(4) Scale. Platinum renders the delicate gradations of the negative, from the highest light to the deepest dark, better than any other printing medium. The only ones which vie with it in this respect are carbon and gum, and with these it is difficult to get absolutely pure highlights except by brush development. No such difficulty exists with platinum.

(5) Esthetic quality. The sheer esthetic quality of platinum, irrespective of the subject matter or treatment of the picture, surpasses that of any other printing medium. The image, consisting of very minute particles of metallic platinum, lies in, not on, the paper, so that paper and image give the effect of a homogeneous unit, rather than that of an image lying on a more or less – often sadly less – sympathetic support. This full advantage may be taken of the inherent beauty of a fine hand-made paper. Further, the image is of an absolute matte quality, with no slightest suggestion of lustre, this being a characteristic which is highly prized by artists.

These advantages and disadvantages are of course what might be termed abstract merits and faults; that is, variations from, or approximations to, the ideal. It will readily be seen that they are shared, to a greater or lesser extent, by all other mediums.

Now for the actual working of the process.

The Negative. — Writers on platinum printing commonly say that the medium demands a strong negative, but this means simply that it has so long a scale that to exhaust this scale a vigorous negative is required. Of course it is by no means imperative, any more than with any other medium, to use the full scale of the paper; one may make a print in high, middle, or low key quite as well in platinum as in any other process – in fact, high keyed effects are best obtained in platinum. Also, the formulae which will be given later, together with simple variations in development, make it possible to get prints of practically any degree of contrast from a negative of almost any quality, from a mere ghost to one which is so strong as to be unprintable in any other medium except multiple gum. Broadly speaking, to secure a given effect with an average sensitizing mixture, the negative should be a little stronger than it would be to secure the same effect on a medium-contrast chlorobromide paper.

The Paper. — Any paper which will stand half an hour’s soaking on cold water may be used, provided it is not too highly glazed. This means, obviously, that any good linen paper is suitable, and many others as well, though the best possible grade should generally be used, in the interest of permanence. The texture and color may be almost anything that the worker desires; I have made satisfactory prints on the following papers:

Whatman Cold Pressed, medium and smooth. The Whatman rough is rougher than will generally be desired for anything except broad effects, 11 by 14 or larger.

Lalanne, Michallet, and Strathmore charcoal papers. The Strathmore works very nicely indeed, and is somewhat more uniform in quality than the others, but the grain is more regular, and therefore somewhat less interesting.

Imperial Vellum, Imperial Vellum tissue, and Shidzuoka Vellum, as well as Barcelona, all from the Japan Paper Company. The Shidzuoka has a rather fibrous texture, which loosens up in the processing, so that the result is not very satisfactory in a size smaller than 8 by 10, or even for half and full length figures of this size. For larger sizes, though, it is very delightful. The Barcelona is a white stock (the vellums are slightly yellow) and works very nicely; the texture of the finished print is exceptionally good. Loveliest of all – though not so easy to work as some other papers – are the tissues; a good platinum print on a fine tissue has an esthetic quality which rivals that of a fine etching, and which is absolutely unparalleled by any photographic medium whatever.

Various Strathmore drawing papers.

Various linen note-papers, as well as sundry writing, drawing and detail papers.

In addition to the above, I have seen very beautiful prints made on the parchment–like paper in which butter is wrapped.

If the worker cannot find something to suit him in this list, he must be hard to please; however, this is very far from exhausting the possibilities, and everyone can experiment for himself.

The Chemicals. — (1) Potassium chloroplatinite. This should be dry, clean, ruby-red crystals. Be sure that it is fresh, and do not get the yellow chloroplatinate, which is useless for this purpose.

(2) Ferric oxalate. This should be in the form of dry, bright-green scales. If it shows any brownish color, or if the scales have a tendency to stick together, the sample is not fresh, and should be rejected. Do not get the ferrous oxalate, which also is useless for platinum work.

(3) Oxalic acid.

(4) Potassium chlorate.

The last two should of course be of chemically pure grade, but neither is likely to give any trouble on account of confusion or staleness.

(5) Potassium oxalate.

(6) Mercuric chloride. This will be needed only if warm black or brown tones are desired. Note that it is a rather dangerous poison, and should not be left where children or irresponsible persons can get at it.

(7) Monobasic potassium phosphate. This will be needed only if cold black tones are desired.

(8) Hydrochloric acid, c. p.

Making Up the Solutions. — In making up the sensitizing solutions, distilled water should be used throughout, and for convenience in dissolving the salts in may be warmed to 180ºF. The solutions, however, should be used at room temperature.

The sensitizing solutions should be kept in the dark, where they will keep indefinitely; brown glass bottles are satisfactory, or if clear bottles are used, they may be covered with black paper. It is convenient to use bottles with rubber stoppers, these stoppers being fitted with medicine droppers, but such droppers should be checked for uniformity, since they are apt to vary considerably in the size of the drops discharged.

Make up three solutions, as follows:

(1) Water … … … 2 oz.
Oxalic acid … … … 10 gr.
Ferric oxalate … … … 240 gr.

(2) Water … … … 2 oz.
Oxalic acid … … … 10 gr.
Ferric oxalate … … … 240 gr.
Potassium chlorate … … … 4 gr.

(3) Water … … … 2 oz. 3 dr.
Potassium chloroplatinite … … … 210 gr. (1/2 oz. av.)

The developing solutions are made up as follows, it being advisable to use distilled water, though this is not imperative unless the local tap water is exceptionally impure.

Water, hot … … … 48 oz.
Potassium oxalate … … … 1 lb.

This gives neutral blacks. If cold blacks are desired, use

Water, hot … … … 48 oz.
Potassium oxalate … … … 9 oz.
Monobasic potassium phosphate … … … 3 oz.

For warm tones, use

Water, hot … … … 48 oz.
Potassium oxalate … … … 1 lb.
Mercuric chloride … … … q.s.

to give the desire warmth. It is not possible to say just how much of the mercury salt will be needed, as this depends on the worker’s requirements. However, it will be well to start with, say, 60 grains, and add more if necessary.

All the above developers keep well, and may be used repeatedly; in fact, they improve with age, and should never be discarded, but should be kept up to volume by adding fresh stock as required. In using, it is well to pour off the clear solution from the mud which settles at the bottom. I might add that not long ago I developed some prints, with perfect success, in a developer which was seventeen years old.

The clearing bath consists of

Water … … … 60 oz.
Hydrochloric acid, c.p. … … … 1 oz.

This is most conveniently made up at the time of use, and should be discarded when used; there is no advantage in keeping it, and to do so risks imperfectly cleared prints.

Since the clearing bath given above tends to remove some of the warmth of tone from a mercury-toned print, it is often advised to use a 1:300 bath instead of 1:60, but I am more or less doubtful of the wisdom of doing so. It is unquestionably the case that if the stronger bath is used, it is necessary to add more mercury to the developer for the given warmth of tone; it seems to be the case that part of the warmth is due to the size of the platinum grains, and part ti iron salts remaining in the paper. If these iron salts are entirely removed, the print will be permanent, but if some are left, the whole print will darken with exposure to light. Just where the dividing line between permanence and impermanence lies, I am not sure; I have prints twenty years old, which were cleared in the weaker bath and are perfectly fresh and bright to-day; on the other hand, I have similar prints which have darkened conspicuously. The safest plan, where permanence is important, seems to be to use the stronger bath.

Other Materials.— A flat board or sheet of glass on which the paper may be pinned or clipped for sensitizing; pushpins or spring clips; clips and a line to hang the paper up for drying; a small (1-ounce) graduate or other non-metallic receptacle for mixing the sensitizer; a brush for spreading the solution. The most satisfactory brush is the type known as a Japanese paint brush, to be obtained in various Japanese art stores. Its merits are two; first, the hairs are short and are set in a thin row, wherefore they do not take up and waste much of the solution; and second, it contains no metal. However, if such a brush cannot be obtained, an ordinary flat paint brush may be used, provided the bristles are set in rubber. Three or four inches is a convenient width for any size paper up to 20 by 24 inches.

Sizing the Paper.— Not many linen papers will need to be sized before the first sensitizing, but this may be necessary with some softer papers, and is very likely to be required before second and subsequent sensitizings when multiple prints are to be made.

Either gelatine or starch may be used. If the former is preferred, soak 80 grains of hard photographic gelatine in 4 ounces of cold water until well swollen, then melt it in a double boiler and apply it while hot with a sponge or brush, rubbing it well into the pores of the paper. If starch is to be used, rub a little laundry starch to a thin cream in cold water, then heat, with stirring, until it clears, and apply as above; it may be thinned down with cold water.

It is convenient to size the paper in large sheets, cutting it up afterwards, and if several prints are to be made with one sizing formula, it is both convenient and economical to sensitize in this manner.

Sensitizing.— Five formulae are given for the actual sensitizing mixture, these giving different degrees of contrast.

For very soft prints

Solution 1 … … 22 drops
Solution 2 … … 0 drops
Solution 3 … … 24 drops

For stronger prints

Solution 1 … … 18 drops
Solution 2 … … 4 drops
Solution 3 … … 24 drops

For average prints

Solution 1 … … 14 drops
Solution 2 … … 8 drops
Solution 3 … … 24 drops

For strong prints

Solution 1 … … 10 drops
Solution 2 … … 12 drops
Solution 3 … … 24 drops

For extreme contrast

Solution 1 … … 0 drops
Solution 2 … … 22 drops
Solution 3 … … 24 drops

It will be observed that 24 drops of solution 3 are always used; that solution 2 is the one which controls contrast; and that in each case the total is 46 drops. Intermediate proportions of 1 and 2 may of course be used; these quantities are merely general in their application.

The quantity given, 46 drops, will coat one 8 by 10 sheet of medium paper if the Japanese brush is used; for very rough papers, or with an ordinary paint brush, which absorbs much of the solution, a larger quantity may be required.

If the sensitizer is used in these proportions — 46 drops for an 8 by 10 sheet — it will be found that it will not give very rich darks; the full scale of gradation will be rendered, but the deepest shadow will probably not be darker than a dark gray. If rich blacks are desired — and the depth of the blacks is one of the great merits of platinum paper — double or even triple the amount of sensitizing solution should be used. This may be applied in any of three ways; by brushing on the larger quantity at the first sensitizing; by sensitizing, drying the paper, then brushing on the additional amount; or by sensitizing, printing, developing, clearing, and drying the paper, then sensitizing and printing a second or a third time. For special effects, the last method is sometimes valuable, but generally speaking, the first is to be preferred; the second is not altogether satisfactory, especially with the softer papers.

The sensitizer having been measured out and well mixed, cut the paper an inch or so larger all around than the finished print is to be, pin or clip it in a horizontal position on the board or glass, pour the sensitizer on it in a pool, and quickly spread the solution back and forth over the paper, brushing it up and down and crosswise, and continuing the brushing until the paper is surface dry. The solution spreads very easily and quickly as well as uniformly, and only by extreme carelessness can it be made to streak; there is no need for the meticulous blending which gum printing demands. If an ordinary paint brush retains enough of the solution so that by using it with a little more than normal pressure another sheet — at all events a small one — can be sensitized without mixing up additional solution. Since the sensitizer is rather expensive, this represents an obvious economy.

The method of sensitizing which is used in making the commercial paper is to float the paper for a predetermined time on the solution, or to draw it over a definite length of tray containing the sensitizer. This method produces excellent results but requires a much greater investment than the average amateur will care to make, and the brush method is quite satisfactory, though rather more expensive so far as individual prints are concerned.

Up to the time when the paper is surface-dry, all operations may be conducted in an ordinary room, but the paper should be dried in the dark, or by a weak artificial light. The drying time will depend on the paper; generally speaking, it should be dry in not less than five nor more than ten minutes after hanging up, and if it does not dry spontaneously in that time, drying may be hastened by an electric fan or over a gas stove. If a stove is used, great care must be taken to prevent scorching, as the sensitizer will scorch long before the paper does, giving ineradicable dark areas in the finished print, this injury not being developed until the print is developed. The drying time is by no means critical, and some hard papers must be allowed to dry more slowly if the image is not to wash off during development, whereas some soft ones must be dried more quickly to keep the finished print from having a dull, sunken-in appearance. For the average paper, though, five to ten minutes is a good general time.

Keeping the Paper.— The operation of sensitizing is so quick and so easily carried out that there is very little point in making up the paper except for immediate use. However, if the worker desires to have a stock on hand, he can make up the quantity, which will keep for some time provided it is stored in the dark and is kept absolutely dry. It must be stored in a glass or metal receptacle, hermetically sealed, with a preservative included. Surgeon’s — not electrician’s — adhesive tape may be used for sealing, and the customary way of making the preservative is to make a tight roll of asbestos, about two inches long by half an inch in diameter, soak this in a saturated solution of calcium chloride, desiccate over a stove, and wrap it in a thin, porous paper. If the sensitized paper is not stored in this manner it deteriorates very rapidly, giving degraded lights, and even if properly stored it will not keep in perfect condition for more than about three months. It is true that bright prints may be made on old paper by using potassium bichromate in the developer, as described below, but on the whole I feel it is less troublesome and more satisfactory to make the paper up fresh as required.

Printing.— It is not possible to say how long the printing time will be, since this depends on the negative, the printing light, and the effect desired. However, as a general guide I may say that printing for a normal effect in clear July sunlight, my own negatives, which are somewhat softer than the average, will require from three to five minutes’ exposure; at a distance of a foot from a small twin-carbon arc lamp, using White Flame carbons, the time is about the same. The sensitized paper is a lemon-yellow, and in printing it turns to a light brown, this visible effect serving, after some experience, as a guide to the time required. But this change is less apparent with the hand-sensitized than with the commercial paper, and in any case a good deal of knowledge and judgement is required to estimate the depth of color with the accuracy which is demanded by the careful pictorial worker, so I prefer to print by time. The margins trimmed from the paper may be used as test strips, being printed, developed, cleared and rinsed, then dried over a gas stove, this last being necessary because the prints dry down darker than they look when wet. The whole operation of running through a test strip need not take more than ten or fifteen minutes at the outside, and you will then be sure of not wasting one or more sheets of paper.

Some writers recommend using a sheet of rubber behind the paper in the printing frame, to protect it from dampness, but this advice comes from England, where the climate is more damp than ours. I have not found this precaution necessary in the neighborhood of New York, but it is well to avoid extremely damp weather for platinum work.

Development.— The print need not necessarily be developed at once, since there is no continuing action, as there is with bichromated colloids. But if it absorbs moisture from the air, which it will do very readily, the lights will be degraded, so unless it is to be developed immediately on taking from the printing-frame it should be returned to the storage box.

Normally, development takes place at room temperature, anywhere between 60ºF. and 80ºF. being satisfactory. To develop, simply slide the print edgewise into the tray of developer; break any air-bubbles which may form; and rock the tray until development is complete, which will be one or two minutes. There is no danger of overdevelopment; the action will proceed as far as the exposure calls for, and then will stop, not can it be forced if the print is under-timed. At room temperature there is no need for extreme care to see that the developer covers the print in an even flow; a brief stoppage will not leave development marks.

Clearing, Washing, and Drying.— Three successive baths of five minutes each in the dilute hydrochloric acid solution given above, followed by fifteen or twenty minutes in running water, or half a dozen changes, and the print is ready for drying, which may be either spontaneous, under pressure from blotters, by an electric fan, or by heat. If tissue is being used, the second method is probably best, since the thin papers sometimes have a tendency to buckle, but aside from this no special precautions against curling need be taken; in the absence of a gelatin emulsion, the prints tend to lie flat.

Decrease Contrast.— If a very soft print is to be made from a negative so strong that the desired result cannot be secured with the first sensitizing formula, a further degree of softness can be obtained by using the developer warm. It will be necessary to print lighter than normal, the depth of printing depending on the temperature at which the developer is to be used, both of these factors being correlated with the amount of softening desired. The developer may be used as warm as 160ºF., and the temperature controls not only the contrast but also the warmth of color of the print. When using warm developer, it is imperative that it be flowed over the surface of the print in a smooth, even sweep, as the slightest stoppage will certainly produce an ineradicable line of demarcation.

The addition of a very slight amount of hydrochloric acid to the developer — say, a few drops of the 1:60 clearing bath to 30 ounces — will result in a very conspicuous diminution of contrast in the print. When this is done, it is not necessary to heat the developer.

Increased Contrast.— If increased contrast, beyond that given by the fifth sensitizing formula, must be had, there are several methods of obtaining it.

Printing for a long time in a weak light will give a decided increase, as with any printing medium. I have known a strong print to be secured from a ghost of a negative by printing, during several successive days, as far as possible from the window of a north room, for a total of forty-eight hours. If this plan is followed, normal development is used.

Printing deeper than normal, and diluting the developer to correspond, has a marked effect, though if the developer is diluted to less than half strength the image may be grainy.

A very marked increase of contrast may be obtained by printing deeper than normal and adding potassium bichromate to the developer, even so small a proportion as ten grains of the salt to thirty ounces of solution having a decided effect. The depth of printing must of course be correllated with the amount of potassium salt, and both with the increase in contrast desired. This method is sometimes useful in getting bright prints on stale paper, and I have successfully used it in printing a sunlit snow scene on paper which was two years old and useless with normal developer. If carried too far, graininess will result from this technique also. The potassium bichromate does no harm to the developer, but the salt becomes exhausted with use and more must be added from time to time if the effect is to be maintained.

These methods for modifying contrast are chiefly useful with the commercial paper; when using the hand-sensitized, it is generally better to depend on varying the sensitizing formula, as the variations given will take care of any reasonable negative.

Waxing.— It sometimes happens, especially with a print in which there are very heavy blacks, or if the print has been allowed to soak too long in the developing and clearing baths, that the shadows have a dull, sunken look. In such a case, life can be restored to the print by simonizing; of course this spoils the characteristically matt surface of the print, but it restores the brilliant appearance which it had when wet. Any of the beeswax-and-turpentine combinations may be used, such as Simoniz Wax, which gives the print a faintly greenish yellow cast; Johnson’s Automobile Wax, which is a pure yellow; or 2-In-1 Show Polish. This yellow tone may be helpful, especially with portraits or summer landscapes, in conjunction with the warmth of a mercury developer, but if it is not desired the print can be brightened by dipping it in French picture varnish, diluted with alcohol, or into a solution of gelatine, twenty grains to the ounce, the latter being used warm. The easiest way to apply the wax is to brush it over the dry print with an ordinary paint-brush, then polish it off with a stiff vegetable brush.

The shadows of a heavy print may be somewhat lightened by waxing in the usual manner, then melting the wax into the paper over a stove or over any flame. Do not allow the turpentine to catch fire, or the print may be smoked up and spoiled, and do not omit the polishing, or the wax will probably be streaky. If the wax is melted in, the characteristic platinum surface is not destroyed, as is the case when it is polished.

Spotting.— It is not necessary to spot with water-colors and a brush, as some workers do; a carbon spotting pencil, sandpapered to a needle point and delicately used, is perfectly adequate and much easier to handle.

Cleanliness.— Cleanliness in working platinum is by no means so vital as with bromide, but a lot of trouble in the form of spots and stains can be avoided by cleaning trays and graduates thoroughly each time they are used. The best way to clean them is to throw in a handful of Gold Dust, add enough water to make a thick paste, and scrub this around with the hand, afterwards rinsing it completely out.

Cost.— Here is a bit of bad news. At the current prices, the work as I have outlined it will require an initial investment of $30 to $35. This can be cut down by purchasing the platinum salt — which is by far the most expensive item — in smaller quantities, but then the relative cost of the prints goes up, since the price of the vital chemical is much higher in small lots. Buying as I have indicated, the cost of an 8 by 10 print will be around 40c to 50c if the formula given above is used, and double that if the quantity of the solution is increased, to get heavy darks; and 11 by 14 will, correspondingly, cost about $1 or $2. These costs will doubtless horrify those workers who are accustomed to turn out 8 by 10 bromides in quantity, for 8c to 10c apiece, but the beauty of a fine platinum print on hand-made paper so surpasses that of the best bromide that the difference will not disturb the photographer who cares for really fine results rather than for quantity production. In this connection, let me quote from Pictorial Landscape Photography, by the Photo-Pictorialists of Buffalo; the sentiment is so well expressed, and is so perfectly in line with what I have preached for years, that I should like to see it painted in large letters on the wall of every workroom used by anyone who aspires to be a pictorial photographer:

“One picture of outstanding excellence is worth more than, not one dozen, nor one hundred, but and infinite number of mediocre and undistinguished ones.”

Factory production methods may be all right for automobiles, fountain pens, and bathtubs, but they have no place in art.

Final Remarks.— It may be thought that I have given an astonishing amount of space to what I claim as the simplest of printing methods. This is because I wished to cover all possible ramifications of the subject, and, so far as might be done, leave no possible loophole for failure. Of course it is not feasible to cover everything, to give precise instructions for every step; in platinum printing, as in all other human activities, no one has ever yet discovered a satisfactory substitute for brains, and there will be points which the worker must determine for himself. happily, in the making and use of platinum paper, these doubtful points are few; and not only in the beauty of expression but also in ease of working does this process so far transcend most other printing mediums that I am confident of its appeal to those photographers whose aim is a few exquisitely beautiful prints rather than a mass of insignificant ones.