Cyanotype exposure time - results of survey - AlternativePhotography.com

Experienced cyanotype printers share their knowledge in this big survey of cyanotype exposure time from all over the world. If you also would like to take part in the survey, please answer the questions here.

How long and how do you print/expose your cyanotype?

Cyanotype exposure time using the sun

Atlanta, GA, USA (from Nicole Tineo)
Winter midday – using a black&white 4×5 negative: 9 minutes

San Pancho, Mexico (from Anne & Elena).
Winter midday – Photogram on pretreated fabric. Rinsed in the ocean: 18 minutes.

South Austin, Texas, USA (from Spiffy Tumbleweed).
Summer midday – using transparency negatives: 2-4 minutes
Summer afternoon – using transparency negatives: 3-5 minutes
Winter midday – using transparency negatives: 3-7 minutes

Bergen, Norway, 60 deg north (from Ole Tjugen)
Summer midday – using in-camera film negatives or glass plates: 5 minutes
Autumn afternoon – using in-camera film negatives or glass plates: 20 minutes
Winter: not possible

Boston, USA (from Malin Fabbri)

Winter midday – using transparency negative: 30 minutes

Bridgnorth, Wolverhampton, UK (from Jo Mills)

Summer midday – using the sun and acetate transparency negatives: 1-2 hours

Winter midday – using the sun and acetate transparency negatives: 2-4 hours

British Columbia, USA (from Susan Huber)

Summer midday – using the sun and Mike Ware’s cyanotype formula: 5 minutes

Summer midday – using the sun and the classic cyanotype formula: 10-15 minutes

Chester County, Pennsylvania, USA (from Neila Kun)
Summer midday – using a paper negative: 1 – 5 minutes
Summer afternoon – using a paper negative: 10 – 30 minutes

Colorado Springs, Colorado, USA (from Drew O’Kane).
Summer midday – using inkjet transparency negatives: 15-20 minutes
Winter midday – using inkjet transparency negatives: 10-20 minutes

Edmonton, Alberta Canada 53 deg north (from Jackie Van Fossen)
Summer midday – using a paper negative and printing on fabric: 10 – 15 minutes
Winter midday – using a paper negative and printing on fabric: 15 minutes

Guanajuato, México (from Gabriela Farías)

Summer morning: 5 min – using transparency negative

Summer midday:4 min – using transparency negative

Summer afternoon:7 min – using transparency negative

Winter morning: 10 min – using transparency negative

Winter midday:8 min – using transparency negative

Winter afternoon: 15-20 min – using transparency negative

Grand Forks, BC, Canada; right on the 49th parallel (from Randi DeLisle).
Times for using Sparco brand transparencies, printed on Xerox desktop laser printer (good density) or on Minolta copier (not dense enough, so I use two negatives layered together)
Summer midday – depending on negative density: 1 – 3 minutes

Summer afternoon – depending on negative density: 1 – 3 minutes
Fall midday – depending on negative density: 1,5 – 4,5 minutes

Göteborg, Sweden, latitude 57 degrees 44 minutes north (from Mats Leidö).

Summer morning using traditional enlarged negatives, kodak sheet film: about 20 – 40 minutes

Summer midday using traditional enlarged negatives, kodak sheet film: about 7 – 15 minutes

Summer afternoon using traditional enlarged negatives, kodak sheet film: about 25 – 50 minutes

Harlow, Essex, England (from Mick Saunders)
Summer, ealy evening – in bright evening sun in and out of cloud using transparency negative: 12 minutes 45 seconds.
Summer, afternoon – in watery sun using transparency negative: 9 minutes 30 seconds.

Heidelberg, Germany (from Manfred Raida)
Summer morning – using film negatives and transparencies: not tested – too direct sun
Summer midday – using film negatives and transparencies: 10 – 20 min
Summer afternoon – using film negatives and transparencies: 30 – 60 min
Winter morning – using film negatives and transparencies: not tested
Winter midday – using film negatives and transparencies: 10 – 30 min, best is no direct sun
Winter afternoon – using film negatives and transparencies: over 1 hour

Johannesburg, South Africa (from Jarryd Bekker).
Midday – using 4×5 Illford negatives: 8 minutes

Juneau, AK, USA, 58 deg north (from David W Riccio)
Summer midday – using oiled paper negatives: 20 minutes
Summer midday – using plants / photograms: 40 minutes
Winter midday: 60 minutes

McMinnville, Tennessee (from Richard Swim)
Summer midday – 2:45 minutes
Summer afternoon – 3:00 minutes
Winter midday – 15-30 minutes

Kalingrad, Russia, 55 deg north (from Pavel Nastin)

Summer morning – using transparencies or tracing paper: 15 – 25 minutes

Summer midday – using transparencies or tracing paper: 5 – 12 minutes

Summer afternoon – using transparencies or tracing paper: 10 – 25 minutes
Winter morning – using transparencies or tracing paper: 4 – 6 hours
Winter midday – using transparencies or tracing paper: 4 – 6 hours
Winter afternoon: not possible to print

Lausanne, Switzerland (from David Gagnebin)

Winter sunny (11 am to 15h30 pm): 20 minutes.
Negative are well contrasted xerox print (BW on a HP laserjet 2600). Size is 19.5 cm (more or less 8 inches) square. Original is BW polaroïd, scanned and inverted on psd.

Los Angeles, USA – sunny but smoggy! (from Gustavo Castilla)
Summer morning – using transparency negative: 15 – 20 minutes
Summer midday – using transparency negative: 15 – 20 minutes
Summer afternoon – using transparency negative: 15 – 20 minutes

Melbourne, Australia (from Wendy Currie)
Summer morning – using transparency negatives: around 15 minutes
Summer midday – using transparency negatives: 10 minutes
Summer afternoon – using transparency negatives: 10 minutes
Winter – using transparency negatives: 30 minutes

New York, USA (from Robert A Schaefer Jr)
Summer midday – using digital transparency negatives: 15 – 20 minutes
Summer afternoon – using digital transparency negatives: 20 – 30 minutes
Winter: Use lightbox

New York State, USA (from Mark)
Summer midday – using litho film negatives or transparencies: 10 minute.

Winter midday – using litho film negatives or transparencies: up to an hour

North Carolina, USA (from Diana Bloomfield)
Summer midday – using film negatives or Pictorico transparencies: 10 – 15 minutes
Winter midday – using film negatives or Pictorico transparencies: 30 minutes

Norman, Oklahoma (from Mary)
Summer morning – using transparency negative: 12 minutes
Summer midday – using transparency negative: 9-10 minutes
Summer afternoon – using transparency negative: 12 minutes

San Francisco, USA (from Elizabeth Graves)
Summer morning – using translucent paper negative: 4 minutes
Summer midday – using translucent paper negative: 3 – 3.5 minutes
Winter morning – using translucent paper negative: 4.30 – 6.30 minutes
Winter morning – using inkjet transparencies: 3 minutes
Winter morning – using overdeveloped dense silver negative: Up to 26 minutes

Stockholm, Sweden (from Malin Fabbri)

Winter day – using transparency negative: 1 day if sunny, 2 days if cloudy

Summer day – using transparency negative: 30 minutes

Sydney, Australia (from Jun Chen)

Autumn morning (April, 9am): 4 min

Toronto, Ontario, Canada (from Andrew Mckinnon)
Summer morning – using transparency negatives: 20 minutes
Summer midday – using transparency negatives: 10 minutes
Winter morning (diffuse sunlight) – using transparency negatives: 1 hour and 50 minutes
Winter midday (diffuse sunlight) – using transparency negatives: approx 40 minutes
Winter afternoon (direct, hard afternoon sunlight) – using transparency negatives: approx 30 minutes

Tucson, Arizona, USA (from Rebecca Bushner)

Summer morning – using the sun and transparency negatives: 4-8 minutes

Summer midday – using the sun and transparency negatives: 3-6 minutes

Summer afternoon – using the sun and transparency negatives: 4-8 minutes

Winter morning – using the sun and transparency negatives: 20-30 minutes

Winter midday – using the sun and transparency negatives: 15-25 minutes

Winter afternoon – using the sun and transparency negatives: 25-45 minutes

Venezia, Italy

Summer midday – using inkjet transparency negatives: 4-5 minutes (from Giuseppe Perezzan)

Jamaica (anonymous contributor)
I expected my exposures to be less than 10 minutes in the bright Carribean sun, but surprisingly, in some cases they were over 30 minutes! This was directly on the seaside. When I moved up the hill about 1/4 mile my exposures shortened! The best I can figure out is that the sea air has water particles that interfere with the transmission of UV light.

Los Angeles, California, USA (from Nan Wollman)
Summer andWinter – using transparencies as negatives: I put the print out on a sunny day in the morning and take it in at the end of the day all year ’round. I’ve been doing it this way in San Antonio, Texas, Rock island, Illinois, Lynchburg, Virginia, Smithville, Tennesse. All places i have lived! My film are very dense and contrasty. The chemisty will only go “so-dark”. You can do an exposure in 10-20 minutes, but longer = deeper. Bleaching, using very diluted bleach, I can bring back some of the details.

Winston, Georgia, USA (from Barbara White).

I use Cynanotype and Van Dyke Brown alternative processes.

Summer midday – using transparency negatives or photograms: 45 minutes to an hour.

Cyanotype exposure time using lightboxes

Using 3 tubes from JBSsystems light, in a row. Each is T8-36W uv lamp. negative is app. 30 cm (12 inches) from the source: 25-30 minutes. Negative are well contrasted xerox print (BW on a HP laserjet 2600). Size is 19.5 cm (more or less 8 inches) square. Original is BW polaroïd, scanned and inverted on psd. (from David Gagnebin).

Using a home-made lightbox with 20-Watt BLB (dark purple) lamps (8 lamps spaced 1.5 inch apart/3.8cm apart), transparency negatives on Pictorico OHP and the Cyanotype II formula: 9 – 12 minutes (from Felix Bezanis).

Using a custom lightbox and Pictorico negatives: 10 – 15 minutes (from Jason Revell).

Using a lightbox: 15 – 20 minutes for fabric (from Jackie Van Fossen).

Using a UV lightbox and negative film: 10 – 15 minutes (from Steve Peet).

I use a hand made lightbox large enough for 20×24 prints because it is more consistent. Exposures run around 8 minutes. Less will give you a lighter blue. More does not give enough medium tones from the negative. I use transparency negatives made on the computer, a copy machine, or hand drawn with markers. Sometimes I use objects for a photogram (from Marydorsey Wanless).

Home-made lightbox: 5-30 minutes depending of the density of the negative (from Alain Carrillo).

Using a lightbox and enlarged negatives bergger film or digital negatives I expose for about 30 minutes. With oiled paper negatives I expose for about 1 – 1.5 hours and photograms about 30 minutes (from Jill Enfield).

I exclusively print in self-made wooden light-boxes with lid up to 56×68 cm fitted with 6 RTL Tubes for UV-B light 365 mn, Philips no. TL20W/05 60 cm. UV-B is hazardous to your skin, so that’s why the lid, which I close during exposure time. The distance between the 6 tubes in the box should not be larger than the diameter of the tubes. The glass plate above the tubes is 8 mm. thick. I use a light-clock between the mains and the plus of the box. That clock can be set with intervals of 15 minutes. My exposure-time is 3 hours. To avoid over-heating of the glass-plate (I never use a fan which produces to much dust) I set the clock as follows: 45 minutes on, 30 minutes off, so the total-time is 4 hours + 30 minutes. My negatives are black/white enlarging papers Multgigrade IV RC up to 50×60 cm. Prior to exposure, I strip off the RC back off the negative, so I become a negative with an RC front and a paper back. I rub that back in with paraffin-oil to make it more translucent. (if not, the exposuretime will be 7 to 8 hours and after a number of prints the RC back will become brown-yellow due to the UV-B light, which will not happen with an oiled paper back). Furthermore the beautiful fine texture of the RC-paper will be shown in the final print. (from Jan van Leeuwen).

UV lightbox and transparency negatives takes 20-25 minutes (from Wendy Currie).

I use a self-made lightbox. Exposures run 20-30 minutes, depending on the negative. For negative I prefer Tri-X, but have used Bergger 200 – much slower exposure in camera than Tri-x (from Jan Kapoor).

I use platinum box with exposures of 5-20 minutes. Nowadays, all negs made on computer on plastic inkjet (from Karl P. Koenig).

I use a light box, homemade, containing 6 UV flouresecent tubes (from Bruce Behan).

Home made light box – 12 15 watt UV/BL fluorescent bulbs and digital neg on Pictorico (from Bill Leigh).

300W Osram Ultra-Vitalux lamp. Because of the intense heat generated by this bulb, it must be fitted in a ceramic holder. With the print set at 40cm below the lamp, exposure is about 10-12 mins (less at shorter distances, of course). (from Brian Young)

Using other UV-lights to expose cyanotypes

Using a NuArc 1000W Quartz Lamp with Integrator, the times are 10 – 30 minutes depending on the material being exposed, longer for real plants, less for digital and traditional negatives (from David W Riccio).

A metal halide vapor lamp for greenhouses takes 20 minutes (from Ole Tjugen).

My lightsource used to be an old tanning device, but some of the tubes broke and I replaced all of them with 6 Philips 60cm TLD 18watt 33 tubes – for normal lighting purpose. They all have their own individual parabolic reflector and the light intense. Using transparency negatives I expose 20 – 30 minutes (from Hans van Erp).

BLB tubes; distance circa 3 cm; exposure times from 10 min to 1 hour, but this depends of course of the kind of negative. A transparancy is around 10 minutes, a waxed paper negs up to 30 minutes (from Henk Thijs).

Using UV lights and a normal density negative: 1 – 3 minutes; if printing with an exceptionally dense negative, it can take as long as 20 minutes, sometimes longer (from Diana Bloomfield).

Standard U.V. facial tanning unit for 99 Euro. The distance from printing frame – about a foot and exposure 12 minutes (from Karl Burke).

I use a neon light “black light bulb”, OSRAM, 36 watt at a distance of 30 cm and a paper-negative. The right exposure time is 35 – 40 minutes (from Davide Rossi).

Tanning unit with one high pressure bulb with about 400 W power. The exposure lasts from 7 to 10 minutes depending on coating, envionmental conditions and type of development. I exclusively use inkjet printed negatives. The separation is made with a point to point calibration routine with preview of the final print (from Kai Hamann).

I use a Phillips facial solarium supported in a wooden cradle 20cm from the contact frame. My exposure times are normally between 10 and 25 minutes for in-camera negatives (from John Brewer).

Chemistry used for toning cyanotypes:

Tea (from Pavel Nastin and Steve Peet).
Aiming for a blue-grey color I use a with a 5% solution of lead acetate. 10 minutes will bring the color to its final state – any more is a waste of time. Sometimes I soak the just-exposed print in a mild acetic acid solution (supermarket vinegar is fine for this) to lengthen the tonal scale, which also turns the color more towards blue than cyan (from Felix Bezanis).
I tone in strong Lipton tea (yellow label). I do not bleach first, instead letting the blues go blue-black and the highlights oddly pinkish. My tapwater is slightly acidic, which affects the tone (from Ole Tjugen).
Bleach, tea and tanic acid (from Gustavo Castilla).
Bleached with washing soda and toned with teas (from Richard Swan).
Bleach with washing soda and tone black tea (from Jackie Van Fossen).
I tone using recipes from The Book of Alternative Photographic Processes by Christopher James or ordinary tea bags. You can get great browns by soaking overnight (from Marydorsey Wanless).
Bleach using hydrogen peroxide (from Alain Carrillo).
I use tannic acid in one tray and a small amount of borax in another, and I switch the print back and forth in the two trays. By doing this, I have achieved a lovely split-toned effect, of violet and a deeper tone of blue. It varies, depending on long I keep the print in the toners. I also use the borax by itself, which offers up a really deep blue (from Diana Bloomfield).
Sodium carbonate and tannic acid, hydrogen peroxide and pyrogallic acid. (from Jill Enfield).
Coffee (from Mark).
I tone my cyanotypes with tannic acid and sodium carbonate (from Wendy Currie).
I recently experimented with toning a selection of my 5×7 still life pinhole images in very strong tea. I really liked the varied tonalities I got. Didn’t care for the strong tea smell in the darkroom, however:-) (from Jan Kapoor).
I’ve had pretty good luck with espresso coffee WITHOUT pre-bleaching. I just save whatever leftovers there are from our stove-top espresso maker until i have enough that i can add 50% water to this and get enough in a tray. This seems to work pretty well with prints that are a few days old, and I don’t soak them first. I suspect that the tap water is a bit alkaline, so this may account for why it works effectively for me without pre-bleaching (from Andrew Mckinnon).
I bleach using several alcalic chemicals like ammonia or potassium hydroxide depending on the wanted effect. The toning is made with tannic or gallic acid. Fine corrections are made with ph management or a second toning after drydown (from Kai Hamann).
I have used Lipton tea for it’s tannic acid, not green tea. This turns the print a warm reddish brown in color, including the highlights (from Neila Kun).
I use tannic acid (from Nan Wollman).
I use Folger’s crystals, baking soda, and ammonia in various combinations. Folger’s and ammonia seem to give a chocolate tone when transfered back and forth several times (from Drew O’Kane).
Bleach with solution of 1 tbsp. trisodium phosphate (TSP) in 1 litre distilled water, rinse under running water, then tone with tea bath (from Randi DeLisle).
Black coffee, whatever’s left in the pot. This tones down the blue and gives a very nice old timey look (from Spiffy Tumbleweed).
Brown Toner using ammonia and tannic acid. Eggplant Black using sodium carbonate and tannic acid. Black using Ilford Universal Paper Developer and tannic acid. (from Mary)
Tea
for an antique effect. I have also used
diluted blackcurrant juice
which seems to lighten the print slightly, and tone the paper (from Jo Mills)
Tannic acid, nitric acid
, and occasionally
strong tea
(from Rebecca Bushner).
I tone the cyanotypes in
gallic acid
(from Susan Huber).
Tannic acid and black tea (from Gabriela Farías)
Strong coffee. I add 1 litre of boiling water to 20g of instant coffee. I cool and bottle it, then prepare a weak solution of bleach by dissolving one quarter of a teaspoon of anhydrous sodium carbonate in 1 litre of water (this is approximately a 0.5% solution). For the best results, I let the print age for a few days, then start the toning process by giving it a 5 minute warm water bath in a developing tray. In another tray, I prepare a bleach solution. I transfer the print to the bleach for not more than 60s and then put it back in the water bath and wash it thoroughly. I pour the coffee toner into a third tray and leave the print to soak face down for at least an hour. I wash well and dry flat (very important) to avoid stains appearing in the margins. I recommend using 300g/m2 Hahnemühle matt watercolour board dried flat if you want your whites white. I put the wet print inside a folded towel and pat dry for a few seconds before laying it on a shelf.
For sepia tones I use strong green or black tea. I find that the final colour of a toned print is very dependent on the pH and mineral content of the local water. (from Brian Young).

Recommended suppliers in the US

Recommended suppliers elsewhere

Photographers’ Formulary 11 recommendationsBostick and Sullivan 8 recommendationsBlueprintables (pre-coated material) 2 recommendations

Artcraftchemicals 4 recommendations

Adorma (kits) 1 recommendation

B&H (kits) 1 recommendation

Freestylephoto 1 recommendation

Ace Chemicals, South Africa, 1 recommendationBoom B.V, Holland, 1 recommendationCMC chemicials, Italy, 1 recommendation

Experilab, South Africa (kits), 1 recommendation

Farmacia Paris, México D.F, 1 recommendation

Fotomatica, Italy, 1 recommendation

Interchema Antonides – Netherlands, 1 recommendation

Merck, Germany, 1 recommendation

Nymoc chemicals, Toronto, 2 recommendation

Permadocument / PH7, Belgium, 1 recommendation

Rayco, UK, 1 recommendation

Science Supply, Melbourne, Australia, 1 recommendation

Sigma-Aldrich in Germany & Holland, 2 recommendations

Silverprint, UK, 3 recommendations

VWR – International supply house, 2 recommendations

For contact details for these suppliers, see the Directory of Chemical suppliers.

Cyanotype printing tips and experiences:

Make test strips! When possible I try and make test strips, but not possible for somethings like plant material as it is only good for a single exposure. (from David W Riccio).
Choose your paper! I find that choice of paper is, by far, the biggest contributor to thesuccess or failure of a cyanotype. Make sure the paper is Neutral pH or slightly acidic (good luck finding these!) or it will surely fog. I have not had good experience with Type I cyano (classic formula) – it requires too much exposure time, and does not achieve strong enough shadow density for my taste. The cyanotype II formula is easy enough to make, and lasts forever if kept in the refrigerator, whereas the “classic” formula grows nasty colonies of mould (from Felix Bezanis).
Using the Cyanotype Rex it is possible to achieve excellent results and it is a lot less complicated than the cyanotype II method. For kicks I sometimes use Amoniom Ferric Oxalete and find it give good results (from Gustavo Castilla).
There is no correct exposure just what you think is best! (from Steve Peet).
Don’t be afraid to mix your own solution. Buying kits is expensive. It is hard to go wrong with cyanotype! (from Marydorsey Wanless).
A double coating helps for better contrast (from Henk Thijs).
I often print the same negative, first in platinum, and then in cyanotype. I like the results, making the platinum/palladium print richer and the split-toning effect when combined with the cyanotype. It’s especially nice with landscapes, where the lighter tones of the sky often pick up the blue of the cyanotype, which is really wonderful – as though I actually had some control over things! (from Diana Bloomfield).
Right exposure times! A great way to figure out a cyanotype exposure is to look at th.shadows – when they are purple and somewhat shimmering – it is ready to go (from Jill Enfield).
Use the cyanotype I method, not the cyanotype II (from Mark).
Mix up stock solutions under tungsten light and always use distilled water, (respirator, gloves etc.). Also, coat the paper under tungsten light. Don’t overload the brush when coating the paper or ‘pooling’ will occur. Really important to keep notes on exposure times, type of paper used, date, and test strips. Find a watercolour paper that you like which gives an intense blue. Stick with it for a while to test out exposure times for each type of negative used eg. inkjet, Type 55 Polaroid, Pictorico, laser, photocopies, 5″x4″, oiled paper etc (from Wendy Currie).
After I develop the prints, I put them in a wash of 2% hydrogen peroxide and tap water to enhance the blues – just before the final rinse. I prefer the “old” (cyanotype I) process as far as using the kit as opposed to the new (cyanotype II) one which Michael Ware in England invented. The new one is very time consuming to prepare, and I feel the old one is actually better – and so much easier to prepare (from Robert A Schaefer Jr).
I find I have to be very sure of coating on the “right” side of the paper, which with Crane’s Platinotype or Arches Aquarelle hot press is the smoother side. Humidifying the darkroom also helps get a good smooth coating. Also, I can’t wait for dry-down to experience the intense blues, so I dip the prints in a weak solution of hydrogen peroxide: the blue intensifies instantly; then I wash them again (from Jan Kapoor).
Often make gum bichromate OVER cyan (from Karl P. Koenig).
I’ve found that the cyanotypes can be partially toned quite effectively by masking what you don’t want toned with rubber cement. Obviously this has to be done quite carefully because the sharp edge between the two shows. I’ve also found that cyanotypes can be done quite effectively on glass if you replace half of the water in the recipe with knox gelatine (the recipe on the package), as long as you “develop” in cold water. with warm water the image will peel off the glass. the result is fairly “thin”, but it’s quite effective with a light-colour behind the glass (from Andrew Mckinnon).
Try to work constantly and carefully observe if any unexpected or variant results appear. Factors like paper ingredients, humidity and exposure time/intensity, ph and traces of different chemicals in the water for development have an extreme impact on the final print (from Kai Hamann).
Be careful! Wear proper safety equipment – gloves and mask. Lots of ventilation. Experiment to get the best results (from Neila Kun).
I wash the prints in the shower, and use a good water filter to take out chlorine otherwise the washing can bleach out the print (from Nan Wollman).
I use Mike Ware’s New Cyanotype. It works fairly well, and the convenience of one solution is very nice. I would, however, say that his formulation is not necessarily faster printing than the traditional formula. Do not turn your transparencies red! The highlights do not clear, and you get a somewhat solarized look as well. Stick with the regular black ink setting (from Drew O’Kane).
For beginners, I think it is best to make and use a UV light box for exposure – it is more dependable and consistant than the sun. This is important for the beginner who is struggling with learning about papers, brushes, coating techniques, etc. Using a UV light box removes one variable and helps ensure that early success, rather than early discouragement is what the beginner will experience (from Bruce Behan).
Some cities add an alkali to the water to raise the pH. This will destroy any cyanotype. I take 35% Muriatic Acid from Home Depot, dilute it 5:1 with water, then add 3 ml dilute HCl to each liter of water as my developing rinse. This somewhat deepens the blue, but also prevents the alkali in the water from eating the image (from Bill Leigh).
I test exposure using a Stouffer TP 4×5 graphics tablet was 12.5 minutes where step 1 is DMax. Step 11 gave a just perceptible tone. Steps 4 to 1 on a tablet exposed at 12.5 minutes but undeveloped showed pseudo-solarization. For flat negatives I use a small amount (1 – 2 drops from an eye dropper) of 1% potassium dichromate in the sensitizer. For negatives with too much contrast I use 1cc – 5cc glacial acetic acid to 1 litre water (from John Brewer).
Prints clear best if the developing water is warm. When exposing under sunlight (particularly during fall,Winter, or spring),it is important to angle the exposure frame so it’s perpendicular to the sun’s rays – the exposure time will be shorter, and the print as sharp and clear as possible (from Randi DeLisle).
I’ve tried printing on terra-cotta and found that the exposure times are increased drastically. After one hour of exposure time, I startedto get images. I’m going to try 1.5 to 2 hours (from Mary).
I experimented a lot with controlling contrastto get “punch” in the cyanotypes, full bodied midtone and details in the shadows. A test with a stepped greyscale wedge concluded that I needed to raise contrast in the shadows, and lower contrast quite a lot in the midtones. With some images I also lowered contrast in a part of the highlights. To get this result with film was difficult, but possible. I used a combination of underexposure/ overdevelopment and overexposure/underdevelopment in at least two stages, for each intermediate copy using my negative sheet film. Of course, today this could be much better done in Photoshop, 2 or 3 moves in Curves would be enough (from Mats Leidö).
Chartpak brand
“Ultra Black, Black or Super Black markers and Prismacolor brand black markers seem to be the best brand for drawing on acetate (from Rebecca Bushner).
If there is humidity I dry the paper with a hairdryer before exposure and after the final wash (from Gabriela Farías).