The Pélegry Calotype Process
These instructions are for the preparation of 40 sheets of 8”x10”. All weights and volumes can be scaled down to smaller formats as required.
The choice of paper is critical. Good results can be reliably obtained using Clearprint 1000H drafting vellum, though the paper has a fine but visible wire-mark that can be seen in contact prints from the calotype. My preference has been to use 70g Chateau Vellum, a 100% linen paper from Ruscombe Paper Mill in France. A new paper, 100% cotton, is lighter and should also work very well, called Timothy 2.0 Calotype, also by Ruscombe Mill. Mark one side of each sheet with a pencil reference mark in one corner. Numbering the sheets helps keep track of them during the processing.
Iodising the Paper
Iodising the paper can be done in normal daylight. Make a batch of fresh whey. You need 500ml and can freeze any excess for future use.Place 500ml of fresh whey into a clean glass bottle or large beaker. In another beaker dissolve 7.5g potassium iodide and 2g potassium bromide in about 50ml of distilled water. In a third beaker, warm another 100ml of distilled water and stir into it 10g lactose powder fully dissolved. Filter both these solutions into the whey and give it a good shake to mix it well. Place this solution in an 8”x10” flat-bottomed tray (the plastic Cesco trays sourced from Adorama or B&H in the US are ideal). Wearing a brand new pair of nitrile gloves, take the first sheet of paper and holding it by diagonally opposed corners lower it on to the surface of the liquid and then immerse it. Using your fingers, force the paper under and remove any air bubbles. Turn the paper over and immerse again, then turn it once more. Using a plastic knife to lift one corner makes this a lot easier. Leaving this sheet in the solution, repeat with the second sheet, again turning it twice. Repeat until the first ten sheets are immersed. Then lift the entire packet and turn it over. The time taken to do all this will have been sufficient to iodise the papers. Lift up the top sheet (which will now be the first one you immersed) and peg it up to dry. Nylon cords strung horizontally and plastic clothes pegs work well. Place a small offcut about 1” x 0.5” of the same paper in the lowest drip corner to ensure even drainage. Hang all ten sheets and allow them to dry. Repeat the procedure for the second batch of ten sheets and so on until you have iodised all 40 sheets. The iodiser will remain good until used up but will only keep for a couple of days in the fridge before the whey goes off. When the papers are bone dry, stack them together and place the stack between clean blotting sheets. Sandwich the bundle between two boards and place a weight on top. Leave them overnight to perfectly flatten the paper. These iodised papers will keep for a long time. I have sensitised some that were a year old and they worked well.
Sensitising the Paper
This stage makes the paper light-sensitive. By immersing the paper in a bath of silver nitrate you produce light-sensitive silver iodide and silver bromide in the paper through the reaction of the silver with the iodide and bromide already in the paper from the iodising stage.For this you need 5 flat-bottomed trays and at least two hours uninterrupted in a darkroom. Tungsten lamps screened with rubylith will be sufficient - you don’t need modern safelight standards. Start with a brand new pair of nitrile gloves. The first stage of the sensitisation process is to prepare the final preservative solution because you need to let it stand for about 48 hours. Take 15g of yellow dextrin powder and add it to about 30ml of distilled water in a beaker. It immediately forms a glutinous lump which you need to work to dissolve using a clean ½” paintbrush reserved for the purpose. To speed things up you can sit the beaker in a hot water bath. Gradually add distilled water until all the dextrin is dissolved. Then filter this into a clean glass bottle containing 300ml of distilled water and give it a good shake. Next, in a second clean glass bottle, add 300ml of distilled water and dissolve in this 15g tannic acid. Be sure to use the light yellow tannin, not the dark brown wine tannin as that would stain the paper. Give the bottle a good shake and leave it for ten minutes or so when it will have fully dissolved. Filter this into the bottle containing the dextrin solution. (Coffee filter papers are fine for this). A yellow precipitate immediately occurs. Let this stand at room temperature for 48 hours during which time it will begin to clear. Pélegry claims it clears in 6-48 hours but in practice it takes weeks to clear fully. It works just fine when cloudy. I leave it 48 hours anyway.
In the first tray place your silver bath, which is prepared by dissolving 50g silver nitrate and 3g citric acid in pure distilled water (Note that in Pélegry’s book he has a typo where he gives the amount of citric as 0.5g. If you use such a small amount your papers are prone to spontaneously darken on drying). If you get a white precipitate it means your “distilled” water is not completely free from chlorides, so just filter it with a fine filter paper to remove the insoluble silver chloride.In the second tray place pure distilled water. In the third tray place a salt solution prepared by dissolving 4g of sodium chloride in 500ml of water. In the fourth tray place distilled water. In the last tray place HALF of your previously prepared dextrin and tannin solution. I sensitise ten sheets at a time. Between each set of ten I stop and filter the silver nitrate bath using a fine chemical filter paper (a coffee filter is not fine enough). If you don’t do this the whey and lactose which leaches into it builds up contaminating the next set of sheets causing them to turn dark spontaneously as they dry. This was a hard-won expensive lesson. Take the first sheet of the batch and immerse it in the first tray, the silver bath. Turn the sheet, turn it again, making sure there are no bubbles trapped underneath. Leaving this sheet soaking, place the next sheet on top, turning twice again. Repeat this until all ten sheets are immersed. Then flip the entire stack of papers over and they are ready for the next step. Lift the top sheet (the first immersed) and holding it by one corner let the excess silver nitrate drip off back into the tray. Then immerse the sheet in the second tray, containing pure distilled water. Turn the sheet and turn again as before. Do the same for the second sheet and repeat until all ten sheets are immersed in the water. Flip the stack of paper then move the top sheet into the third tray containing the salt solution. Again turning the papers twice as they are added, repeat until all ten sheets are immersed. Next comes the wash in the fourth tray. You might consider two trays for this wash and you must ensure all the white precipitate of silver chloride produced in the salt bath is removed. Place all ten sheets into the water of the tray, agitating and turning them twice as before. Change the water 3 times (this is where a second tray of water helps make the washing more thorough by moving between two water trays). After the third change of water, you are ready for the final step. Taking one sheet, let the excess water drain then immerse it in the dextrin-tannin
bath and let it sit alone for 3 minutes. Remove the sheet and hang it by one corner to dry, attaching a small piece of paper to the drip corner. Now take the second sheet from the wash tray and immerse it in the dextrin-tannin bath and repeat the procedure.When the first batch of ten sheets are done and hanging to dry you can filter the silver bath. The dextrin-tannin bath is good for 20 sheets of 8”x10”. After the first two batches you discard the dextrin-tannin bath and replace it with the second half of the solution that you reserved earlier. This is because the dextrin-tannin becomes diluted by the previous wet papers. When the sheets are bone dry I place them all together and the whole stack between blotters and boards under a weight overnight to make them perfectly flat. Under red light the sheets should have a uniform clear creamy colour. They will keep for at least six months provided they are kept in the dark. I place each sheet in a separate film-safe envelope. You can make your own by covering large paper envelopes with thick black PVC plastic sheet cut to size. I usually leave a day between each set of 10 sheets so the silver bath can stand. The organic matter in the silver bath from the paper will turn black within a day. Filter the bath and continue with the next set of 10 sheets.
I use a both UV meter (the UV513AB manufactured by General Tools) and a Sekonic lightmeter to determine my exposure times. As a guide, for a UV level of 1 mW/cm2 I’d give it 2.5 minutes at f/8. If you don’t have a UV meter then as a rule of thumb if it is a nice sunny day with blue sky try 3 minutes at f/8. In shadow or overcast conditions try 6 minutes at f/8.
Pélegry advocates using pyrogallic acid (pyro) for development. However, this is very aggressive and you will get much better control using gallic acid instead. Gallic acid oxidises in solution quite quickly. Of great convenience is to prepare a concentrated stock solution of gallic acid in alcohol which keeps a long time and then make up developer as needed. Prepare a stock solution with 20g of gallic acid dissolved in 100ml ethanol. You need to warm it in a water bath (no direct flame obviously) to get it to dissolve. Then, for an 8”x10” calotype, I make up 100ml of developer by adding 4ml of the stock solution to 96ml distilled water to give 0.8% gallic acid. To this I add 1ml of acetonitrate solution (composed of a mixture of 7% silver nitrate and 14% acetic acid). Sometimes I add the acetonitrate at the start, sometimes I add it after about ten minutes. In this case you need to lift the paper out, add the acetonitrate to the tray and mix it well before returning the sheet to the tray. If the paper is a type which curls badly when wet I add the acetonitrate at the start to avoid the wet-handling of the paper.Arrange 3 trays. The first contains distilled water, the second is for the developer and the third is for a post-wash and also contains distilled water. Pour the 100ml of developer into the second flat-bottomed 8”x10” tray dedicated to this task. Immerse the calotype in the first tray of distilled water. As soon as it is fully wet remove it and lay it face down on the developer. Ensure the back is completely immersed then turn it over and leave it to develop face up. Development takes from 20 minutes to an hour or two depending on how long the exposure has been. Overexposed images that develop in under 30 minutes often lose quite a lot of density in the hypo fix so ideally you want to aim for exposure times that will develop in no less than 40 minutes.
When development is judged complete, transfer the negative to a bath of distilled water for 3 minutes to stop any further development. Change the water twice for a total of three washes of 3 minutes each.
Fixing & Wash
To fix the images, make up one litre of 15% solution of sodium thiosulphate. Divide this between two trays. Fix the negative for 5 minutes in each tray then rinse in water and place into a tray of hypo-clear (1% solution of sodium sulphite). Finally, wash the negative for at least an hour in tap water, changing the water two or three times during this period. The negative is then hung to dry.