Toning prints for image protection

Toning process involves among the most toxic chemicals routinely used in conventional darkroom processing. Please follow standard laboratory safety procedures and use adequate safety precautions. (Caveat: This doesn't mean procedures described on other pages are non-toxic. You are warned by default. Toning processes, however, deserve explicit warning.)

1. Silver images

Metallic silver forming the image in b&w prints is far from inert, and it undergoes chemical interactions with environmental pollutants not to mention moisture and air.

For a long time, inadequate fixing and washing was the accepted dogma for the cause of image deterioration. However, it has become very clear that (1) higher levels of residual thiosulfate than what was considered archival limit would not harm¹ the life expectancy of the material (Kopperl and Hutteman 1988); (2) even the properly processed prints and microfilms are not very stable.

One of the leading threat to the silver is the oxidative agents contained in the environment, which can cause a variety of change to the image, such as discoloration, fading, mirroring, etc. Peroxide is one such oxidizing agent most commonly encountered in film and print storage environments. Although abundantly present, peroxide is weaker than other oxidizing agents present in environment, such as nitric oxide and ozone. Therefore, if prints are given toning treatment for protection, complete protection from severe peroxide attacks should be the minimum practical goal of toning. A report from Image Permanence Institute (IPI 1991) indicates that almost complete protection against peroxide and some, incomplete protection against other more potent agents can be obtained through polysulfide treatment. The IPI previously found that selenium toning was inadequate for protecting microfilm from peroxide attacks. Although we shall review many types of archival toners in this page, if the goal is to provide maximum image protection, polysulfide toner is the toner of choice.

2. Processing sequence

Develop prints

Use of warm tone paper and a warm tone developer is recommended to enhance the hue of the toner. Use of cold tone paper and a cold tone developer is recommended to produce neutral final image, with the only purpose of toning being protection of the image.

Fixing must be done to completion.

A rapid, neutral fixing bath or two-stage fixation is recommended.

Rinse (1 to 3 minutes)

Fixed prints should be briefly rinsed before toning in most toners to avoid staining. The purpose is to remove much of fixing solution, which contains silver-thiosulfate complex ions. If significant amount of silver-thiosulfate complex ions are present in the gelatin layer, it may cause stain during toning. In some rare instances where acid fixer is used, the toner may stain the print even after adequate rinsing. Treating rinsed prints in a 1% sodium carbonate bath before toning is usually helpful in this case.

Bleach the prints

If an indirect toner (most sulfide toners) is used, the prints need to be bleached prior to toning. If a direct toner is used, this step is unnecessary, but prints can be bleached to enhance the hue shift due to toning. After bleaching, brief rinsing is advisable, because contamination of bleach and toner can cause staining.

Tone the prints

Wash the prints.

In case of pure selenium or selenium-sulfide toning, the prints can be washed directly after toning. However, if baryta paper is used, a sequence of brief rinsing, wash aid treatment, and final wash is recommended. In case of polysulfide containing toners, use of sulfite stop bath is strongly recommended as specified below.

Optional treatments

Prints may be treated with any optional steps such as AGFA Sistan, PhotoFlo, etc. before drying.

3. Storage and Display

Although properly toned prints are significantly more stable than untoned b&w prints, a great care should be used to the conditions where the prints are stored or displayed. In particular, humidity control proper choice of storage material are very important.

See Bard (1988) and other resources.

4. Selenium toning

As an image protection, weak selenium toning has been suggested for prints and microfilms (see Lee and Bard 1988 for summary), partly because it changes little on the image contrast, density, hue and grain structure. Weak selenium treatment is also simple and inexpensive. In late 1980's, Image Permanence Institute (IPI) at Rochester Institute of Technology found that such a treatment was indeed ineffective against oxidative attacks. The IPI report recognizes that such a treatment using Kodak Rapid Selenium Toner (KRST) had been effective up to a certain point, but when they tested, KRST did not provide enough protection. (Reilly et al. 1988; Reilly et al. 1991)

The most classic selenium toning bath consists of a solution of sodium selenosulfate. This solution was typically prepared by dissolving selenium powder in heated aquaous solution of sodium sulfite. Such a preparation is not recommended today, because of toxicity of selenium in powder form. This bath has to have a rather high concentration of selenium, and the toning action is slow.

Another classic selenium toning bath was prepared by dissolving selenium powder in sodium sulfide solution. Kodak T-56 and Ilford IT-3 are examples of this category. Prints may be bleached partially or entirely before toning, but this is not necessary. The image is very well protected, and the image hue is expected to be somewhere between that of sepia toning and selenium toning, depending on the degree of bleaching.

Kodak Rapid Selenium Toner is a different story. It takes advantage of the fact that the selenium toning progresses much faster when abundant thiosulfate ions are present in addition to selenosulfate ions. In principle this type of formulation doesn't require sulfide as in the selenium-sepia toner, although it is not imcompatible with it.

The discussion in the IPI report suspects that the image protection provided by KRST in older reports are probably due to incidental sulfiding from some impurities that were present in older shipments of the product, but for some reasons this impurity was eliminated in later productions.

Sodium sulfide is not a very desirable compound to have in products that are meant to be used by most photographers, such as KRST, although Eastman Kodak sells another product (Sepia Toner) containing sodium sulfide. This is because effluence of sulfide is often regulated to a very low level. In waste water treatment, sulfide ions have to be oxidized to sulfite or sulfate form, or removed by forming insoluble precipitates with calcium. Whether Kodak ceased to use sulfide in selenium toner production or switched the chemical supplies to more purer stocks, it makes sense in some sense.

In order to achieve adequate image protection with KRST, prints should be toned for fairly long time in a bath diluted 1+9 or less. The hue change is not necessarily equivalent to image protection. In the case of selenium toning, it is safer to assume that prints must be fully toned, to the extent where change in the image hue observed, to obtain useful degree of protection against oxidative attacks.

This presents a challenge when one wants to protect images without significantly changing the neutral black hue of the untoned prints. This is analogous to the microfilm treatment, since changing in image hue and grain morphology is undesirable in such an application.

5. Sulfide toners

This class of toners convert metallic silver to silver sulfide, partially or completely. Generally speaking, the degree of image protection is very high, but this depends on various factors such as the paper, print developer, toner strength, toning temperature and toning time.

Sulfide toners category   active ingredient   resulting hue   direct   smell   sepia   sulfide ion   sepia - yellow brown   no   yes   thiourea   thiourea   yellow brown to black brown   no   no   hypo-alum   thiosulfate   sepia - brown   yes   no   polysulfide   polysulfide ions   orange brown - purplish brown   yes   yes

With classic sepia toner and thiourea toner, prints are bleached before toning to achieve visible hue shift. This type of toners are called indirect toners. These toners are sometimes called redevelopers. Hypo-alum toner and polysulfide toner do not require to bleach before toning (direct toning) but one can choose to bleach prints before toning to enhance the effect of toning.

Sulfide toning releases hydrogen sulfide gas, with its characteristic rotten egg odor. This gas is toxic at a higher concentration. Therefore, this toning must be performed in well ventilated area. However, thiourea and hypo-alum toners do not give off this smell.

Hydrogen sulfide gas is a potent fogging agent. Open tray toning in sepia or polysulfide toner should be avoided in the darkroom while print exposing and print developing are being performed.

Although not a gas, thiourea is a potent fogging agent. In general, graduated cylinders, stirring rods and trays used for toning purposes should not be used for developing process or emulsion making.

Thiourea is a carcinogen. Observe laboratory safety procedures for carcinogenic materials.

6. Sepia toners

Defender T-42 Bleaching Solution Water   1.0 liter   Potassium ferricyanide   13.7 g   Potassium bromide   27.4 g   Ammonium hydroxide (28%)   1.3 ml   Re-Developing Solution Potassium sulfide, saturated solution   7.8 ml   Potassium alum, saturated solution   1.0 liter   A concentrate solution of sodium sulfide can be prepared by dissolving 15g of sodium sulfide fused or 42g of sodium sulfide crystals in 100ml or water at 65°F . A saturated solution of potassium alum is prepared by dissolving 100g of potassium alum in 1.0 liter of water at 65°F . Prints to be toned shold be very thoroughly washed. Bleach until the image is only faintly visible. Then wash until there is no yellow stain left. Redevelop until the desired tone is reached. Wash toned prints thoroughly. Prints on rough surfaced papers should be dryed before bleaching.

Kodak T-7a Sepia Re-developing solution for chloride and bromide papers No. 1--Stock Bleaching Solution Potassim ferricyanide   75g   Potassium bromide   75g   Potassium oxalate   195g   Acetic acid, 28%   40ml   Water   2L   No. 2--Stock Re-debeloping Solution Sodium Sulfide   45g   Water   500ml   Prepare Bleaching Bath as follows: Stock Solution No. 1   500ml   Water   500ml   Prepare Re-debeloper as follows: Stock Solution No. 2   125ml   water   1L   Immerse print, which should first be washed thoroughly, in the Bleaching Bath, allowing it to remain until only faint traces of the half-tones are left and the black of the shadows has disappeared. This operation will take about one minute. Note: Particular care should be taken not to use trays with any iron exposed, otherwise blue spots may result. Rinse thoroughly in clean cold water as all chemicals must be removed. Place in Re-devbeloper Solution until original detail returns (for about thirty seconds). Immediately after the print leaves the Re-developer, rinse thoroughly, then immerse it for five minutes in a hardening bath composed of 1 part of the hardener recommended for the acid fixing bath (formula F-1a) and 16 parts water. Remove the print from this bath and wash for one-half hour in running water. The color and gradation of the finished print will not be affected by the use of this bath.

Kodak T-10 Sulphide Toner for sepia tones on lantern slides Soluton A Potassium ferricyanide   30g   Potassium bromide   15g   Water to make   1L   Solution B Sodium sulfide, fused (*)   0.9g   Water to make   1L   (*) Use three times the quantity of crystalline sodium sulphide. The well washed slide is thoroughly bleaced in A, washed for 5 minutes, and immersed in Solution B for about 2 minutes until thoroughly toned. The slide should then be washed thoroughly for 10 to 15 minutes before drying. The transparency of the tone is much improved by the addition of a little hypo to the B solution, say, ...4.5 grams per liter.

Kodak T-10a Sulphide Toner for sepia tones on motion picture film Solution A Potassium ferricyanide   20g   Potassium bromide   5g   Water to make   1L   Solution B Sodium Sulphide, fused   1.7g   Water to make   1L   The well washed positive should be bleached thoroughly in 2 to 4 minutes in A at 65F to 70F, so that the image appears uniformly yellow on looking at the back of the film. Then wash 5 minutes and immerse in solution B until the film is thoroughly toned. A trace of iron in the sodium sulphide will do no harm provided the solution is boiled and the preciptated iron sulphide allowed to settle before use. Wash 10 to 15 minutes after sulphideing and before drying.

Kodak T-19 Sulphide Re-developer for sepia tones Sodium Sulphide, fused   21g   Water to make   1L   Use full strength at 65F to 70F.

7. Thiourea toner

Thiourea with sodium hydroxide or other alkaline buffering system can be used in place of sodium sulfide to eliminate odor. This convenience, however, comes with a hazard of thiourea being a carcinogen.

Also, care must be taken to avoid contamination of thiourea into bleach solution, or any other processing solution. This is because thiourea can in certain conditions destroy image forming silver or silver compounds, including silver sulfide.

Defender Varigam toner It is a group of toner formulas published in the early 1940's by the Defender Company3, makers of sheet film and paper for use with Varigam, the first variable contrast paper on the American market (the very first VC paper was made by Ilford). This was a neutral tone paper so these formulas should work on a variety of current papers. There are three variations of bleach and three redevelopers. Bleach B-1 Water   500.0 ml   Potassium ferricyanide   22.0 gm   Potassium bromide   25.0 gm   Water to make   1.0 liter   Bleach B-2 Water   500.0 ml   Potassium ferricyanide   22.0 gm   Potassium Iodide   10.0 gm   Water to make   1.0 liter   Bleach B-3 Water   500.0 ml   Potassium ferricyanide   22.0 g   Sodium chloride   35.0 g   Nitric acid   15.0 ml   Water to make   1.0 liter   (Treat the nitric acid with caution.) Bleach in one of the above bleaches for twice the time it takes to convert the black image. The prints should then be washed in three changes of water or until any yellow stain from the bleach is removed. The prints are then re-developed in one of the following re-developing baths. Redevelop until toning is complete. Toner T-1 Water   500.0 ml   Thiourea   3.0 g   Sodium hydroxide   6.0.g   Water to make   1.0 liter   (Treat the Hydroxide with caution, it evolves considerable heat when dissolving and can cause severe chemical burns on contact with the skin.) Toner T-2 Water   500.0 ml   Thiourea   3.0 gm   Sodium carbonate   45.0 gm   Water to make   1.0 liter   Toner T-3 Water   500.0 ml   Thiourea   44.0 gm   Potassium carbonate   48.0 gm   Water to make   1.0 liter   Various combinatins of bleach and toner will give different tones as shown by the following table: Bleach in   Tone in   Resulting Tone   B-3   T-1   Deep brown, slight purplish tint   B-1   T-1   Deep brown   B-2   T-3   warmth of golden tinge   B-2   T-2   a little colder than above   Increasing warmth with a golden tinge till a bright sunlit type of Sepia is produced with the B-3 - T-3 combination. T-2 can be used instead of T-3 but it gives a little colder color and is given as an alternative when Potassium carbonate is not available. All formulas to be used full strength. Richard Knoppow's note: The above table is copied from the original and refers to the Varigam paper of nearly sixty years ago. The tones produced with modern papers may be quite different. Thiourea (thiocarbamide) makes an odorless redeveloper but is now considered to be a carcinogen so should be handled with care.

8. Hypo-alum toner

Hypo-alum toner is another variant of sulfiding toner, which is an odorless direct toner, but comes with a sacrifice in deep black tone.

Kodak T-1a Sepia Toning--hypo-alum bath for contact papers Cold water   2800ml   Sodium thiosulphate   480g   Dissolve thoroughly, and add the following solution: Hot water (about 160F)   640ml   Potassium Alum   120g   Then add the follwing solution (including precipitate) slowly to the hyp-alum solution while stirring the latter rapidly. Cold water   64ml   Silver Nitrate crystals   4.2g   Sodium Chloride (table salt)   4.2g   After combining the above solutions: Add water to make   4 liters   Note: The silver nitrate should be dissolved completely before adding the sodium chloride and immediately afterward, the solution containing the milky white precipitate should be added to the hyp-alum solution as directed above. The solution should be milky white if correctly mixed. For use, pour into a try standing in a water bath and heat to 120F. Prints will tone in 12 to 15 minutes. ... The bath should never be heated higher than 130F, otherwise blistering, staining and non-uniform toning will result.

9. Polysulfide toning

Polysulfide toners provide direct toning to give darker brownish hue compared to sepia toners. This toning also releases hydrogen sulfide gas, with its characteristic rotten egg odor. This gas is toxic at a higher concentration. Therefore, this toning must be performed in well ventilated area.

Off shelf products include: Kodak Brown Toner (KBT), AGFA Viradon (new version)

T-8 polysulfide brown toner potassium polysulfide   7.5g   sodium carbonate   2.4g   water to make   1 liter

Relatively brief toning is adequate for image protection, but toning to obrain brown hue may take several minutes with neutral toned paper. This can be accelerated by warming the toning bath. The actual temperature should be tested with test prints to ensure lack of emulsion damage, but should not exceed 40°C.

In order to prevent staining and halt toning immediately, use of a sulfite "stop bath" is highly recommended (almost obligatory for succssful toning). Prepare a tray containing 20g or more of sodium sulfite anhydrous in a liter of water. Toned prints are immediately transferred in to this "stop bath" tray. After a few good agitaion, the print can be sent to rinse and final wash processes. Without this step, the margins and highlight areas may exhibit pink or yellow staining, reducing the paper base's brilliance.

Similarly, a toning bath that is weaker than recommended strength or a bath that is exhausted runs similar risk of staining the print base.

Prints treated with this type of toner are well protected against oxidative attacks.

SilverLock

SilverLock is a polysulfide toner developed by the IPI for treatment of microfilm material to provide excellent protection with minimum change of image density, contrast, hue and grain morphology (Reilly et al. 1991).

The toner consists of a highly concentrate solution of liver of sulfur buffered with borax. The working solution is prepared by diluting this concentrate. The composition is similar to Kodak Brown Toner except the buffering is provided by borax instead of sodium carbonate.

The actual range of hue it provides with enlarging papers is unknown, but expected to be somewhat similar to that of Kodak Brown Toner.

10. Combination toning

Combination toners contain both polysulfide and selenium toning agents, converting silver grains to silver selenide and sulfide. This type of toners provide direct toning (without bleaching before toning) to give excellent image protection and darker brownish hue compared to sepia toners. The range of hue provided is a little wider than polysulfide toners. With combination toners, blacks can remain rich black with Dmax enhancement due to selenium toning, while highlights and midtones gain brown hue.

This toning process also releases hydrogen sulfide gas, with its characteristic rotten egg odor. This gas is toxic at a higher concentration. Therefore, this toning must be performed in well ventilated area.

There is no current commercial product of this category. AGFA Viradon and Kodak POLY toner used to be sulfide-selenium combination toners. However, the current version of AGFA Viradon is a plain polysulfide toner, lacking selenium of their old product. Kodak discontinued their POLY toner.

Kodak POLY toner MSDS potassium polysulfide   15-20%   selenium metal   < 1%   sodium carbonate   10-15%   potassium hydroxide   < 1%   water   65-70%

It is possible to reconstitute toners similar to original Viradon⁴ or Kodak POLY toner from KRST and KBT. Richard Knoppow found a few such formulae.

Combiation Toner water   500ml   sodium carbonate anhydrous   160g   Kodak Brown Toner   320ml   Kodak Rapid Selenium Toner   80ml   water to make   1.0 liter   Direction: dilute 1+3 for use. RK does not remember the source of this formula, except it was from a magazine article.

Hue No. 1 Kodak Rapid Selenium Toner   17ml   Kodak Brown Toner   75ml   Kodalk Balanced Alkali   30g   water to make   1.0 liter   Direction: use full strength. Replenish with Kodak Rapid Selenium Toner 1+5, approximately 10ml per ten 8x10 prints. Capacity with replenishment: 150 8x10 prints per gallon. Excessive replenishment will shift the image color toward red. RK found this formula in Kodak's booklet on professional printing.

Hue No. 2 Kodak Rapid Selenium Toner   2.0 ml   Kodak Brown Toner   100ml   Kodalk Balanced Alkali   8g   water to make   1.0 liter   Direction: use full strength. Replenisher: Selenium Toner, 1+19 Replenishment: 30 ml per 10 8x10 prints. Capacity, with replenishment: 150 8x10 prints per gallon. Excessive replenishment will shift the image color toward red. Hue No. 1 is redder than No. 2. No.2 tends to reduce prints so they should be slightly darker than normal. RK found this formula in Kodak's booklet on professional printing.

In all of these formulae, it is recommended to prepare the toning solution in two steps:

Part 1:    Selenium toner and the alkaline agent in half of the water specified.

Part 2:    Polysulfide toner in half of the water specified.

and these parts should be mixed to minimize sediment of solid sulfur, which cannot be redissolved and thus a loss of toning capacity.

In order to prevent staining and halt toning immediately, use of a sulfite "stop bath" is highly recommended (almost obligatory for succssful toning). Prepare a tray containing 20g or more of sodium sulfite anhydrous in a liter of water. Toned prints are immediately transferred in to this "stop bath" tray. After a few good agitaion, the print can be sent to rinse and final wash processes. Without this step, the margins and highlight areas may exhibit pink or yellow staining, reducing the paper base's brilliance.

Similarly, a toning bath that is weaker than recommended strength or a bath that is exhausted runs similar risk of staining the print base.

11. Gold toning

Kodak gold protective solution GP-1 has been recommended to protect images from oxidative attacks.

GP-1 gold toner water   750ml   gold chloride (1% stock solution)   10.0ml   sodium thiocyanate   10.0g   water to make   1.0 liter   Add the gold chloride stock solution to the volume of water indicated. Dissolve the sodium thiocyanate separately in 125ml water. Then add the thiocyanate solution slowly to the gold chloride solution, stirring rapidly. For use: Immerse the well-washed print in the gold protective solution for 10 min at 20°C or until a just noticeable change in image tone (very slight bluish black) takes place. Then wash for 10 min in running water and dry as usual. Capacity: Eight 8x10 prints per liter. For best results, the toner should be mixed immediately before use.

GP-2 is more suitable for large scale processing such as treatment of microfilm.

GP-2 gold toner     GP-2   GP-2R (replenisher)   water   750ml   750ml   gold chloride (50% Au)   0.5g   2.0g   tartaric acid   1.0g   1.2g   thiourea   5.0g   10.0g   sodium sulfate, anhydrous   15.0g   18.0g   water to make   1.0 liter   1.0 liter   The replenishment rate is 20ml per square feet of film processed. Processing time is about 1 minute with good agitation at 27°C .

Kodak T-21 (Nelson) Nelson Gold Toning Bath Toning will require between approximately 5 to 20 minutes. After fixing, wash the prints for a few minutes before toning. Stock solution #1 Warm water (about 125F)   4L   Sodium thiosulfate   960g   Ammonium persulfate   120g   Dissolve the hypo completely before adding the ammonium persulfate. Stir the bath vigorously while adding the ammonium persulfate. If the bath does not turn milky, increase the temperature until it does. Prepare the following solution and add it (including precipitate) slowly to the hypo-persulfate solution while stirring the latter rapidly. The bath must be cool when these solutions are added together. Cold Water   64ml   Silver Nitrate Crystals   5.2g   Sodium Choloride (table salt)   5.2g   Stock Solution No. 2 Water   250ml   Gold Chloride   1g   For use, add 125ml of solution No.2 slowly to solution No.1 while stirring the latter rapidly. The bath should not be used until after it has become cold and has formed a sediment. Then pour off the clear liquid for use. Add the clear solution to a tray standing in a water bath and heat to 110F. The temperature, when toning should be between 100F and 110F. Dry prints should be soaked thoroughly in water before toning. When the desired tone is obtained, rinse the prints in cold water. After all prints have been toned, return them to the fixing bath for five minutes, then wash for one hour in running water. The bath should be revived at intervals by the addition of further quantities of the gold solution No.2. The quantity to be added will depend upon the number of prints toned and the time of toning. For example, when toning to a warm brown, add 4ml of gold solution after each fifty, 8x10 inch prints or their equivalent have been toned. Fresh solution may be added from time to time to keep the bath up to the proper volume. Richard Knoppow's note: It is very important to re-fix the prints after using Nelson's. This step is sometimes left out of the Kodak instructions but appears in the original patent. The reason is that the toner generates some silver halide, which is not toned. This will degenerate and cause staining just as it would in an incompletely fixed print. In some Kodak versions of the instructions its stated that the results of Nelson's are not as permanent as other types of sulfide toning. These are coincident with the lack of fixing instructions. If the prints are properly fixed after toning they should be very permenent.

12. Protection with minimum hue shift

The challange of protecting print images without changing the hue to brown or sepia is a problem similar to the protection of microfilm.

For this goal, it is best to start with cold tone paper and cold tone developer⁵. They can be fully "toned" with minimum hue shift.

One possibility may be to reconstitute a selenium toner containing sulfide by mixing at a suitable proportion a selenium toner and sodium sulfide. This would provide selenium toning and additional sulfiding protection. However, use of sodium sulfide is not very desirable because it is rather unstable, involving a decomposition producing hydrogen sulfide gas. Combination of KRST and KBT is an attractive solution if it can be made to work, however, preliminary experiments proved that this mixture does not provide predictable results for a number of possible reasons. However, a toner made from liver of sulfur and selenium powder without using KRST is still a viable option to pursue.

More conservative approach may be to tone prints in selenium toning bath (KRST diluted 1+19) for 2 to 4 minutes, then toned again in Kodak Brown Toner, followed by sulfite stop bath and washing. Since much of the image is already toned in the selenium toner, the hue shift is kept to a much lower level than when KBT is used alone.

One difficult challange is when the print is made with warm chloride or chlorobromide papers. With some papers, such as Forte Fortezo processed in a warmtone developer, hue shift is apparent with very brief treatment in a weak toning solution. Providing protection to warm toned prints without significantly changing the image hue remains a challanging problem.

13. Non-toning protection

Iodide treatment

Agfa Sistan

This stabilizer protects silver image which is vulnerable to strong oxidizing reagents and environmental pollutants, such as ones from automobile exhaust fumes, present in the air. This chemical contains potassium thiocyanate, which is a rapidly reacting stabilizer that provides protection to silver images. While the prints are being wet treated, this reagent merely converts residual silver halides that remain after fixing process into inert water-soluble silver complexes that are stable to heat and light. More to benefit, some thiocyanates residing in the gelatin layer play an important role when pollutants or strong oxidizing agents attack the metallic or toned silver image. The pollutants try to break and change silver to funny colored colloidal forms. In this process, silver ions are stolen by the thiocyanate to convert to stable silver thiocyanate, thus protecting the image.

This mechanism may serve as a double protection even when the print is toned, since toners usually convert the surface of metallic silver grains into a thin coating of silver sulfide, selenide, etc, but this coating may possibly be attacked by a strong pollutant. Additional Sistan treatment doesn't hurt, at worst. In order to double treat prints, fixed prints should be briefly rinsed and toned, treated in washing aid, and throughly washed. The print should then be treated in Sistan bath, squeezed and dried.

Fujifilm Ag Guard

This is a Fujifilm counterpart of AGFA Sistan⁶. However, the main ingredient of this product differs from that of Sistan. It uses 2-(amidinothio)ethanosulfonic acid, and according to MSDS, its concentration is 0.5 to 1.5%. Richard Knoppow pointed out that there are published data for Ag Guard showing its effectiveness in protecting prints compared to untreated prints, although the protection is not as good as that from any toning process above.

Sistan as a wetting agent for film

Sistan or Ag Guard can be used as a better wetting agent that also stabilizes silver images. This solution can be applied to black and white films immediately prior to drying in place of PhotoFlo wetting agent.

Process washed film in Agfa Sistan stabilizer. However, to avoid residual chemical/mineral trace, increase dilution to 1+400 in distiled water (2.5ml Sistan to make 1 liter). I use an all-plastic spray sold for gardening to spray generous amount of dilute Sistan after the film is fully washed and hung for drying. This washes any impurity from tap water used for washing, and also stabilizes the image.

14. Note

Many of the formulae provided on this page are very old, and the result with modern paper may be different from what is described in each formula. I use selenium and polysulfide toners extensively in my darkroom.

Several formulae were provided by Richard Knoppow and Peter De Smidt. Whenever possible, I cross checked with my reference sources at hand for accuracy, but for some formula, this was not possible. If there is any problem with formulae, please let me know.

15. References

Kodak publication O-3.

Ilford fact sheet "Toning b&w prints" May 2002.

Bard, C. C. 1988. Conservation of Images, The J. of Photographic Science, 36, 99-103.

Lee, W. E. and Bard, C. C. 1988. The post treatment of microfilm with selenium toner to enhance stability in storage under adverse conditions, The J. of Photographic Science, 36, 73-74.

Reilly, J. M., Nishimura, D. W., Cupriks, K. M., and Adelstein, P. Z. 1988. Stability of black-and-white photographic images, with special reference to microfilm, Abbey Newsletter, Vol 12, Number 5.

Reilly, J. M., Nishimura, D. W., Cupriks, K. M., and Adelstein, P. Z. 1991. Sulfiding for Protection for Silver Images. Final Report to the Office of Preservation National Endowment for the Humanities, Image Permanence Institute, Rochester Instute of Technology.

Lee, W. E., Wood, B. and Drago, F. J. 1984. Toner Treatments for Photographic Images to Enhance Image Stability. J. of Imaging Technology, 10, 119-126

Notes

¹ Indeed, the study at IPI showed that a small amount of residual thiosulfate provided incidental sulfiding to the silver grains, providing some useful protection. However, it is not practical to purposely leave the optimal amount of thiosulfate in print material. It is strongly recommended to tone important prints without relying on any incidental sulfiding effect of residual thiosulfate.(back)

² See note on Defender Company below.(back)

³ The Defender company was bought by the DuPont company in the mid forties. It continued to do business as DuPont-Defender until the late 1950's when DuPont decided to get out of the consumer photo business.(back)

⁴ On bottles of the original Viradon, selenium was clearly indicated as an ingredient. On the other hand, the "New" Viradon, which became distributed ca. 2001 and after, does not contain selenium according to its label and other manufacturer's publications.(back)

⁵ Phenidone-ascorbic acid developer with liberal dose of benzotriazole makes excellent cold tone developers, providing blue black hue before toning, which tends to stay neutral black even with very strong selenium toning.(back)

⁶ As far as I know, Fujifilm does not export chemical products to North American market. The MSDS referred here is provided in Japanese.(back)