Figure 8.1. Aquilegia, classic cyanotype, 11″ × 14″ © Eugene Starobinskiy 2017
Figure 8.2. Rising, from the series Out of The Blue (Part I of A Million Suns), collaged cyanotype with digital drawing, 11.5″ × 17″ © Jonah Calinawan 2013
If the cyanotype solution is mixed and ready to use, a standard printing time (SPT) has been determined as outlined in the Digital Negatives for Cyanotype chapter, and an appropriately curved negative has been created according to that chapter also, it is now time to coat, expose, and process a print.
Cyanotype is very user-friendly when it comes to brushes. Cheap foam brushes from the hardware store, natural hair hake brushes, synthetic fiber brushes—all work. My favorite for classic cyanotype is the 2″ Connoisseur 150 series hake brushes because they are absorbent and springy. Since they have a stitched ferrule I can soak them after a coating session in plain water for hours without worrying about a ferrule rusting. For combination or new cyanotype I prefer a 2″ synthetic bristle brush because it is coated more thinly to prevent pooling of chemistry and resultant splotching and crystallization (see Troubleshooting Cyanotype), and unless you brush very carefully, strokes can be visible. The synthetic fibers are softer and more refined.
1. Note: If you live in a dry climate or want to experience smoother prints, pre-humidify the paper by creating a makeshift humidity chamber of a tray filled with water, a screen on top, and another inverted tray on top of this to retain the moisture. Leave the paper in this chamber until limp and cool, overnight, or even permanently. Pencil in the size of the negative on the paper. For an 8″ × 10″ use an 11″ × 14″ sheet. For clean white borders, tape off the area with low tack masking tape and coat within the taped borders.
2. For classic cyanotype, measure out ½ teaspoon of Solution A and ½ teaspoon of Solution B into a cup and mix together. This is enough for an 8″ × 10″ on 11″ × 14″ paper. For new cyanotype, a single solution that requires a thinner layer, measure out ½ teaspoon of solution for the same size print (perhaps extra to charge a dry brush). Rule of thumb is it is about 1 drop of solution per 2 square inches, and a ml contains 20 drops. I recommend adding 1 drop of 5% Tween per ml of new cyanotype solution to help the paper absorb and to perhaps increase Dmax.
3. Pour in a line along one edge of the area needing to be coated and immediately begin brushing the solution horizontally and vertically until it covers the area completely and evenly.
4. Hold up the coated paper vertically by one side and let the solution flow downward to even out the brush strokes. Immediately turn the paper 90° before any solution drips off the paper onto the counter and let it again even out downward. Repeat this on all four directions until the solution evenly covers the entire surface with no puddles or areas of drips. A small piece of paper towel can sop up the excess solution at the edge if necessary because that excess solution “blooms” back into the print area and creates marks. Classic cyanotype takes a while to sink into the paper fibers, so it is a good thing to even it out with this technique. New cyanotype absorbs a bit more quickly into the paper, and since you use less solution it is important to smooth out all brush strokes at the offset before holding the paper vertically for that extra solution to even out.
5. Once the paper is evenly coated, hang it or lay it flat in the dark to dry (hanging minimizes pooling and splotching with new cyanotype).
• Some double-coat cyanotype for deeper blue. I have never found this necessary and, in fact, I found it pooled more and created splotches that bloomed into the image area with edges of white when not coated carefully. It is definitely not necessary with new cyanotype. If you want to try it, let the first coat dry for 20 minutes and then coat again.
• In case you do not have an adequate dark area, I have left classic cyanotype out in regular light bulb type room light for two days (not sun!), developed it in water, and have seen no evidence of residual exposure. Test your dimroom light by doing the same. Put a quarter on top of a small piece of coated paper and leave it out in your room light for the time you want to test—always make it overkill—and then see if the paper comes clear in a five-minute development. That will tell you how safe your light is in the room.1 Be sure to test both classic and new cyanotype with this method because new cyanotype is more sensitive.
Depending on the climate, coated paper takes ½–1 hour to dry. I expose the paper as soon as it is dry to the touch but still somewhat limp and cool, about ½ hour. Pre-humidifying paper so it is limp and cool and coating and exposing as soon as it is dry to the touch produces a much smoother, less grainy print; it is best practice for both classic and new cyanotype, and especially so for new cyanotype because it greatly minimizes NC’s splotching issues.
How long does coated paper last?
I have no problem with using coated paper for a couple days, but paper that is much older is slower to expose, prints less contrasty, and the Dmax or darkest blue is not quite as dark. As one author said, “Paper will keep for weeks but the blue is never so bright as when the paper is freshly prepared.”2 It is best practice to be consistent with this and coat and expose within the day, but paper doesn’t magically go off in 24 hours. One well-known cyanotype printer coats a bunch of paper at once and uses it for a month. In the summer he merely stores the coated paper in the fridge.3 Minimizing light, temperature, humidity, and air allows coated paper to last longer, but watch that the paper has remained bright green and not turned blue-green4 which will result in a fogged, dull print.
Coating washi and tissue-thin papers
Tissue-thin papers require a different coating technique. They soak up more chemistry in general. With some, the solution soaks right through the paper to the coating surface below. You cannot just pour solution onto the paper in a line on one side like with other papers. Coat these papers either one of two ways:
1. Pour a line of cyanotype solution on a level piece of glass.
2. Pick the paper up by the edges and form it into a u-shape.
3. Touch the bottom of the u-shape to the solution starting at one edge and then lay the entire width of the paper down in the line of solution.
4. In an even movement, slowly drop the paper down flat, watching that the solution soaks up all the way to the paper edges. This takes a bit of practice to know how much solution to puddle on the level piece of glass that will soak the entire sheet.
5. Let the solution even out for a while and then keep flat to dry.
or
1. Fill a cup with solution that is wide enough to fit the brush.
2. Lightly dip the end bristles of the brush to load it with solution.
3. Brush a horizontal swath of solution on the top edge of the area needing to be covered, the entire length of the area.
4. Load the brush again and brush another swath of solution overlapping and parallel to the previous coat.
5. Do this brush by brush until the entire area is covered.
6. Take the brush and do the same with vertical strokes from one side of the print to the other.
7. Once the area is evenly coated let the solution even out and then keep the paper flat to dry, which may require a paper towel underneath to absorb excess chemistry.
Vellum papers such as Wyndstone, Opalux, Vidalon, and Pergamenata, when brushed with solution, spring up into a scroll that is impossible to stretch out flat. There are two ways to work with this stubbornness. One is to pin or tape down the paper on all four sides before coating and leave it to dry pinned or taped in place. The other is to cut a much larger sheet of vellum than necessary and coat a smaller center of the sheet; this way you can easily cut off the cockled edges and the paper will in general lie flatter.
Cyanotype prints can be exposed either in an indoor exposure unit or outdoors in the sun. Exposure units are perfectly predictable and consistent but about two stops slower (4× the exposure time) than the sun and they require an initial investment of $$; the sun is not so predictable but ¼× the exposure time of an indoor exposure unit and it’s free. With care in observation, and keeping a detailed log of exposure results at different times of the day, weather, and season, you can print fairly predictably outside in all seasons, including extremely cold weather. See the Ballpark UVBL Exposure Times chart pp. 96–97 for some time suggestions (all times are for classic cyanotype 10/10 and new cyanotype 200 ml dilution).
Figure 8.3. Note how short the exposure times, measured in minutes, for new cyanotype (bottom three lines) are in comparison with classic cyanotype (top three lines). Note also that exposure time decreases slightly for each process when an acid is used in the water bath, so it is important to calibrate the time based on the acid used. Prints were exposed in an Edwards UVBL unit.
If you have read the Digital Negatives for Cyanotype chapter and found the correct exposure time for the paper you are using, under UVBL there is nothing to do but place the negative, emulsion to emulsion, on the coated and dried paper and expose it for the determined time.
If you are printing outside in the sun, it will be of great benefit to expose one step wedge print first to determine printing time for that moment, given different weather and seasonal uv amounts (see the Digital Negatives for Cyanotype chapter for how to determine standard printing time). Otherwise, a guestimate for exposure between 10AM and 2PM during late spring to early fall sun is 5–15 minutes for classic cyanotype and 1–5 minutes for new cyanotype.
In order to print by inspection, you will need a hinged back contact frame that allows checking of the exposure without disturbing the negative registration. Make sure the contact frame makes a very snug contact with the negative/paper sandwich so when checking exposure you will not move the negative out of registration. You can do this by adding sheets of watercolor paper inside the contact frame. Do not use cardboard because it does not bend well enough to peel back to check on the image.
1. Expose until the borders of the print that are not under the negative are completely solarized to a lighter silver-blue. This color is much different between CC and NC; with CC it is a dark, reversed navy. With NC it is a bright silver blue-white, and on some transparent vellums the deepest shadows become invisible.
2. Bring the contact frame inside away from bright sunshine or window light, and open the back of the contact frame carefully and on one side only.
Figure 8.4. This seems really obvious, but this is a side-by-side comparison with under- and over-exposure. What might not be so obvious is how the highest detail in the clouds still did not print after gross overexposure, showing how lowering the ink density on a negative is sometimes warranted for classic cyanotype.
3. Look at the deepest shadows in the image area; they, too, should be solarized and lighter, like the borders. Look at the highlights of the image. They should look overexposed, with only specular highlights green. Anything still bright yellow-green will wash out to paper white in general. The print as a whole should look quite overexposed. Err on the side, always, of overexposure because you can always develop longer to remove some print density but you can’t develop shorter as it risks not removing all the iron from the print.
4. Process the print, dry, and assess. Record the paper name, cyanotype dilution, exposure length, time of day, date, weather (bright sun, cloudy, etc.) and any other pertinent exposure information in a notebook, and or on an edge of the print itself (best).
• There is no problem exposing prints one by one and saving the processing steps until the last one has been exposed, provided the exposed prints are kept in the dark while awaiting processing.
• To understand how many steps are lost and then regained during processing and drying, print a step wedge and put a pencil mark where there is detail in the highest highlights, just before maximum white. Then note where that detail is when the step wedge is processed and dried.
• To understand how much exposure is necessary to get maximum blue but not so much that the darkest blue begins to lighten, overexpose a step wedge and put a pencil mark where the first darkest dark step begins to lighten and solarize. After processing and drying, note if there are any steps that are slightly lighter in the darkest area. The step just below that first slightly lighter step indicates the best exposure time.
• Papers differ in exposure time, exposure scale, color of blue, and darkness of blue. Some papers are faster and some are slower. The speed can be affected by the alkalinity of the paper and also how much the paper absorbs chemistry. I find the more absorbent the paper is, the longer the exposure scale. The color of blue can range from turquoise (greener) to royal (purpler) blue.
• “Apparently a portion of the ferrous salt first formed by the reducing action of light reacts further with a portion of the Prussian blue to form the white insoluble ferrous ferrocyanide. After the print is washed thoroughly and dried, the ferrous ferrocyanide is oxidized gradually by the air to form further amounts of ferric ferrocyanide (Prussian blue). This explains why the cyanotype darkens after being subjected for a considerable period to the action of the air.”5
The following table lists the exposure times I calibrated for classic (CC) and new (NC) cyanotype on a number of papers. I tested a 10/10 classic cyanotype formula and a 200 ml new cyanotype formula. If using classic cyanotype with more FAC, e.g. a 20/10, or a more concentrated new cyanotype solution (100 ml or 150 ml instead of 200 ml), your exposure times will probably vary, but once one paper is tested, it will be easy to extrapolate from this chart how other papers will respond.
A few interesting observations surfaced with the data. Exposure times generally decreased with acid development. Papers that are slow to expose are often the alkaline ones and those unsuitable for cyanotype. Papers that are quick to expose are often less alkaline, or alkaline-free, thinner, and more absorbent. [Note: I include the exposure times for no acid and sulfamic acid for cc and no acid and vinegar for NC for comparison purposes only. I would not recommend those developments as mentioned further on. ]
As always, your results may vary (YRMV): UVBL units differ somewhat, and water supplies differ drastically, in which case merely use the charts to clue you in to slower versus faster papers. As we all know, nothing is cut in stone with cyanotype!
Figure 8.5. See how vinegar and citric acid extend the exposure scale of classic cyanotype.
Exposure scale (ES) is a term that refers to how many steps print on a step wedge from maximum black to paper white. Only one maximum black step is included in the counting. Though often photographers include paper white in their ES, I not only don’t include paper white but I only include the last pale blue step that still has a definable edge mark, and thus these exposure scales err greatly on the side of under-representation by perhaps a minimum of two steps or .2.
Exposure scales can be short or long. I have measured as low as a 1.0 ES on a paper with no acidic development to a 2.8 using new cyanotype and sulfamic acid development. This means that the former paper only printed 10 steps on a 31-step wedge (very short scale) and the latter 28 steps (very long scale). A short ES can mean a “soot and chalk” print or one that is way too contrasty with blocked up shadows and blown out highlights if the digital negative isn’t designed to match this short scale. In general, a longer ES is easier to work with, and better able to express the entire tonal range of the image from deepest shadows to highest highlights.
One of the reasons for cyanotype’s continued and increasing popularity is that aside from only two chemicals to make up the solution, it requires only water to process a print. It is as low tech a process there is. Even though low tech, it is still important to pay attention and be consistent, especially when processing. If the cyanotype print is left in the wash water for too little time, iron left in the print will result in yellowed highlights and wreak havoc down the road, fading the highlights to gray.6 If the print is left in the wash water too long, it fades quite dramatically. If the wash water is alkaline, the print not only fades, but also turns to a brown or gray color. Here are some suggestions:
• Test the wash water with litmus paper to make sure it is neutral (pH 7). This is usually the case with well water, but not always. City water can be much different, and vary from winter to summer.
• Watch the temperature of the wash water. Anywhere from cool to quite warm is acceptable, for example, 70°–100°F.
Figure 8.6. See how citric and sulfamic acid extend the exposure scale of new cyanotype.
• Keep the time of the water bath consistent. Don’t pull the print too soon because it looks like all the yellow is gone, or forget the print and leave it in the wash for an hour because of the reasons discussed above.
• Keep the agitation consistent. Agitate continuously for the first few minutes, and then the print soaks face up for the remainder of the wash time, with an occasional wiggle every few minutes to avoid air bubbles which leave round ugly spots of deeper blue.
Processing with acidified water
In my previous almost twenty years of cyanotype practice I had mostly used plain water processing. I used vinegar or citric acid in the water bath occasionally, but my prints tended to end up with stained highlights. When I began the intensive paper testing I had to be systematic about all variables, including development. I chose to compare five types of development: plain water and then water acidified with vinegar, citric acid, hydrochloric acid, and sulfamic acid. I kept an Excel spreadsheet of exposure times and exposure scales of all papers and all five development techniques. I was quite surprised at what I learned. With the first ten or so papers I thought my results were anomalies, but after 136 papers put through the tests I am confident in my conclusion which is this: using some form of acidified water development is a must, and the acid of choice and amount is specific and different for classic versus new cyanotype. In an email, Mike Ware cinched this observation: “The photoproduct iron(II) (ferrous iron, Fe2+) is still bound by ligands (citrate in classic cyanotype or oxalate in new cyanotype) and this molecular complex cannot enter into and make the Prussian blue lattice with ferricyanide in this state. The Fe(II) has to be stripped of its ligands, and acid does just this, because hydrogen ions bind to the citrate or oxalate anions and pull them off the Fe(II).” If you don’t take my word on it, take Ware’s. Here are my suggestions:
• The stronger the acid, the longer the exposure scale, meaning more tones from maximum blue to paper white
• The use of an acid shortens the exposure time, as much as ⅔ stop
Figure 8.7. If a chart like this makes your eyes glaze over, there is one takeaway: use acidic development. The blue line representing no acidic development results across the board in a lighter, duller print. Vinegar and citric acid development are somewhat interchangeable for classic cyanotype (not new cyanotype!), with some papers performing better with vinegar in the development bath and others with citric in the development bath.
• The stronger the acid, the darker the blue/Dmax of the print; not once did the Dmax measure darkest on prints developed in unacidified water
• The stronger the acid, the less wash off occurs
• Classic cyanotype and new cyanotype differ in which acids work best
• The stronger the acid, especially with classic cyanotype, the more the highlights can stain blue
• Classic cyanotype and new cyanotype differ in how much acid can be used without staining of the highlights; for example, I can use very little sulfamic acid in a liter of water with classic cyanotype, but with new cyanotype a 1% sulfamic acid solution or 2 teaspoons in a liter poses no problem
• Classic cyanotype works best with vinegar and citric acid; new cyanotype works best with sulfamic acid; citric acid is an adequate choice, too
• With both formulas there is a sweet spot where enough acid is used to lengthen the exposure scale, shorten the exposure time, and darken the print, before staining of the highlights occurs.
I have found recommendations in the literature to use anywhere from full strength white vinegar (5% acetic acid) to a dilution of 1:10. How strong a solution you can use without stained highlights will have to be found out by trial and error. In my practice, 60 ml/¼ cup per liter is plenty. [Note: Ware cautions against acetic acid because it may form “insoluble colored basic ferric acetate,”7 and though I have not seen evidence of this in my CC prints, NC prints developed in either plain water or vinegar water results in various shades of yellow to brown stain immediately upon immersing the print on all but the most pristine papers made for alt. This is not to say it is ferric acetate—it is probably hydrolized iron8 which shows up most drastically on calcium carbonate buffered papers—but plain water or vinegar are not suitable developers for new or hybrid cyanotype formulas in my experience.]
60 ml white vinegar (4 tablespoons/¼ cup)
1000 ml water
Figure 8.8. Note the comparison between the CC chart, left, and the NC chart here. New cyanotype is much more responsive to acidic development than classic cyanotype. Almost across the board sulfamic acid produces the deepest Dmax because the gray line rises to the top, but citric acid is still an acceptable alternative. Vinegar is not on this chart because it often results in stained, browned prints on any but the papers made specifically for alt (e.g. Platine, HPR, Bergger Cot 320).
1. Add the 60 ml vinegar to a liter of warm water and stir until evenly dispersed. Measure the pH before proceeding. Depending on the water source’s initial pH, this is about a 4 pH. I only measure this once because my well water doesn’t change, but if you are on city water that potentially changes in alkalinity with the seasons, you may want to make a practice of testing the acidified bath with litmus strips once before a printing session and adding more vinegar if necessary.
2. Remove the print from the exposure frame and immerse the whole of the paper at once in the acidified warm water.
3. You can use the entire liter of vinegar water and run perhaps 6 prints through it before it turns dark blue and should be discarded, or you can use about 250 ml/1 cup of vinegar water as a “one shot” wash, discarding after use. This minimizes any potential staining, but with the 10/10 formula I get very little washoff so the vinegar water stays good a long time.
4. Agitate the print continuously in the tray for 1–5 minutes; the water will turn blue, depending on how much wash off occurs.
5. At the end of 1–5 minutes, either throw out the one-shot developer and fill the tray with plain warm water, or transfer the print face down to another tray of warm water for 5 minutes, and wiggle the print intermittently to prevent airbells.
6. At the end of another 5 minutes discard the water and refill the tray with warm tap water again. Soak the print for another 5 minutes and wiggle the print intermittently to prevent airbells.
7. Once the print has gone through 3 washings/15 minutes, it is probably done. Some papers clear in less time, more like 10 minutes. Some take longer to clear. Take note of the time the paper takes to clear of all yellow and use that time in the future.
Figure 8.9. Above is a series of step wedges on fourteen papers, in two columns of seven, new cyanotype developed four ways (from left to right): no acid, vinegar, citric, sulfamic (a couple of the papers are cream colored). Notice how unsuitable plain water and vinegar water is for new cyanotype. All of these papers browned in those two development baths, even the best papers for alt which showed a slight yellow tinge. This is why I always use either citric acid or sulfamic acid development with new cyanotype, and never vinegar or plain water.
8. Hang the print to dry. The print will oxidize from a turquoise to a deeper royal blue within the day, just by virtue of being exposed to the oxygen in the room air. No need to use extra chemistry (hydrogen peroxide) to hurry oxidation along.
9. When the print is fully dry and oxidized, look at the highlights. If the highlights are too white and without detail, revisit the negative and exposure time, not the development time; the development time doesn’t vary unless needing to develop longer for an overexposed print. The negative could be too dense or the exposure time could be too short, but the development time should remain consistent.
Citric acid development for CC
Follow all the steps above, but use 2.5 g citric acid per liter (½ teaspoon). This amount of citric acid is about a 3 pH and a mere 0.25% dilution. Even though most acidified water recommendations are in the range of 1–5% I find staining can occur past the 0.25% amount; it may not for you, so test stronger dilutions if desired.
Citric acid development for NC
Follow all the steps above, but use 10 g citric acid per liter (2 teaspoons). This amount of citric acid is about a 3 pH and a 1% dilution.
Sulfamic acid development for CC
Sulfamic acid is recommended to be used in a 1–5% dilution for new cyanotype9 but for classic cyanotype a mere 0.2% or ¼ teaspoon per liter of water is the most I can use without staining of the highlights, and even with this amount, many papers stain. This is why it is not my favorite acid for classic cyanotype. This will make the water close to a 2 pH. Use it as a one-shot bath, for 30 seconds to 2 minutes maximum.
2 g sulfamic acid (scant ¼ teaspoon)
1000 ml warm water
1. Measure the water into a beaker, and carefully add the sulfamic acid to the water and stir until dissolved, being careful not to splash or spill. It is not terribly soluble so stir a while.
2. Use about 250 ml of this per print. Remove the print from the exposure frame and pour the 250 ml of acidified water onto the print and agitate continuously for 30 seconds to 2 minutes; the water will turn blue, depending on how much wash off occurs.
3. At the end of 30 seconds to 2 minutes, dump the acidified water down the drain and fill the tray with warm tap water. Agitate the print for 5 minutes in the warm water to prevent airbells.
4. At the end of 5 minutes discard the water and refill the tray with tap water again. Soak the print for another 5 minutes and wiggle the print intermittently to prevent airbells.
5. Once the print has gone through 3 washings/15 minutes, it should be done; hang the print to dry.
Figures 8.10–8.12. On the left two house images, note the contrast and speed change of no acid development (far left) versus vinegar development (middle). That is why it is important to calibrate your exposure time and negative density around the development you will be using. On the far right the print was left too long in the water wash. Eventually the entire cyanotype will wash down the drain and leave a pale brown or gray print if you do not time the wash carefully.
Sulfamic acid development for NC
New cyanotype does best with 1% sulfamic acid and a longer development. No need to do the bath one shot, as there is very little wash off and bluing of the water and less potential for the sulfamic acid bath to stain the paper; thus more prints can be run through the liter. It also can take a longer water wash than classic cyanotype after the sulfamic acid bath.
10 g sulfamic acid (2 scant teaspoons)
1000 ml warm water
1. Measure warm water into a beaker, and carefully add the sulfamic acid to the water and stir until dissolved, being careful not to splash or spill. It is not terribly soluble so stir for a bit. Pour the liter into a tray.
2. Remove the print from the exposure frame and put it in the sulfamic acid bath, agitating vigorously and continuously for 2 minutes. Leave the print in the bath for up to 5 minutes if desired.
3. Place the print in another bath of plain warm water and agitate intermittently for 5 minutes.
4. Discard the water and refill the tray with warm tap water again and soak the print for another 5 minutes, wiggling intermittently to prevent airbells.
5. Once the print has gone through 3 washings/15 minutes, it should be done, although some wash up to 30 minutes; hang the print to dry.
Hydrochloric acid development for NC
Vinegar and citric acid are for the most part harmless; they are in our foods, soft drinks, and vitamins. They are my preferred acids for classic cyanotype. Citric acid and sulfamic acid are my preferred acids for new cyanotype. Sulfamic acid is an industrial cleaner and should be handled with care. Even a 1% solution of sulfamic acid can be caustic to hands so use tongs when moving prints, or wear gloves if immersing your hands in the bath. It should be used with all the caution normally in place with all chemistry.
Hydrochloric has often been used in photographic processes. Now it is most used in swimming pools under the name “muriatic” acid. Muriatic acid is readily available at hardware stores. It comes in a ~30% dilution. This is a pungent, heavy acid that should be handled with utmost care. At the risk of being belittled, I will tell you my story. I had a small beaker of muriatic acid, perhaps 10 ml in it, and I left the dimroom for a period of time with the beaker uncovered. When I returned, my litmus strips six feet away from the beaker had turned red from the acid in the air. If I could make such a stupid mistake, my college level students could also. For this reason and for the reason it is corrosive to metal pipes, I do not use it, nor do I teach it. If you are a scientist and work with a fume hood, have at it. Otherwise, stay away. Sulfamic acid does not outgas and does not corrode metal.
Figure 8.13. Watch using sulfamic acid on vellums; this Vidalon vellum bubbled and disintegrated in sulfamic!
There are cyanotypists and platinum printers who use it all the time in their clearing practice. I will not use it in my personal practice because I can see a white gas evaporate into the air when measuring out amounts, which means it is in the air I breathe. I do not have a fume hood in my dimroom, and most people don’t either.
So with that dire warning, if you still want to test it because you are a scientist with a fume hood, the recommended dilution is a 0.1–1% solution. A mere 1 ml (20 drops) of muriatic acid per liter is enough to acidify a liter of water to a 2 pH without staining a cc print. Your results may vary; you may need more. If so, use up to 35 ml muriatic acid per liter to make a 1% dilution, especially for an NC print. It is best to use this as a one-shot bath, 250 ml/1 cup per print, discarding after use.
1–35 ml muriatic acid (1 ml = 20 drops)
1000 ml water
1. Measure the water into a beaker, and carefully add the muriatic acid to the water and stir, being careful not to splash or spill.
2. Use about 250 ml of this per print. Remove the print from the exposure frame and immerse the whole of the paper at once in the 250 ml of acidified water.
3. Agitate the print continuously in the tray for 1–2 minutes; the water will turn blue, depending on how much wash off occurs.
Figure 8.14. Note the lighter turquoise of the unoxidized vellum compared to the deeper blue of the oxidized (with hydrogen peroxide) prints.
4. At the end of 1–2 minutes, dump the acidified water down the drain and fill the tray with warm tap water. This time, place the print face down for 5 minutes, and wiggle the print intermittently to prevent airbells.
5. At the end of 5 minutes discard the water and refill the tray with tap water again. Soak the print for another 5 minutes and wiggle the print intermittently to prevent airbells.
6. Once the print has gone through 3 washings/15 minutes, it should be done; hang the print to dry.
A cyanotype print comes out of the development bath a beautiful soft turquoise blue. This color oxidizes to a deeper blue over 24 hours. If you want to see this change happen immediately you can add a large glug of drugstore hydrogen peroxide to the water wash just after the first acidified water bath. Amount is immaterial; you can see the print immediately darken, and if not, add more. This step is not necessary since the print darkens within 24 hours anyway. It does have a “wow” factor, though. I often add a large glug of the drugstore dilution to my acidified water bath; that way one glug lasts for most of the printing session instead of having to add fresh hydrogen peroxide to the water wash after each time you dump and refill the tray. [Note: add it to the acidified water bath after the acid has been thoroughly dissolved in the water; never add hydrogen peroxide directly on dry chemistry.]
Figure 8.15. Queen Victoria Agave, classic cyanotype, 14″ × 11″ © Eugene Starobinskiy 2017
Endnotes
1. Schaefer, John P. The Ansel Adams Guide, Basic Techniques of Photography, Book 2. Boston: Little Brown and Company, 1998, p. 160.
2. Harrison, Jerome. “The Chemistry of Silver Printing, Printing with Salts of Iron—Cyanotype and Kallitype” in Photographic Times, Vol. XXI, September 4 1891, pp. 440–442.
3. Seigel, Judy ed. The World Journal of Post-Factory Photography. New York: Post Factory Press, April 1998–April 2004, Issue 5, p. 28.
4. Fabbri, Malin and Gary. Blueprint to Cyanotypes. Alternativephotography.com, 2006, p. 19.
5. Farber, Richard. Historic Photographic Processes, A Guide to Creating Handmade Photographic Images. New York: Allworth Press, 1998, p. 59; quote taken from O’Hara, Charles E., and James W. Osterburg. Practical Photographic Chemistry. Minneapolis: American Photographic Publishing Company, 1951.
6. Worthington, J. C. and J. C. Millen. The Photographic Primer, A Manual of Practice. Riverton: The Riverton Press, 1897, pp. 130–131.
7. Ware. Cyanomicon II, History, Science and Art of Cyanotype: photographic printing in Prussian blue. Buxton: self-published, 2016, pp. 216–217.
8. Ibid., p. 176.
9. Ibid., pp. 216–217.