Introduction

We tested the effects of paper type and negative type on cyanotype prints. For paper, we used Abaca Esparta, Crane’s card stock, Bristol, Watercolor, and Beckett Cambric Text. For negatives, we used a silver gelatin negative, a contrasty silver gelatin negative, a handmade wax paper negative, a handmade permanent marker negative, and a digital negative.

Hypothesis: We predict that the low contrast silver gelatin negative and the Crane's Card Stock will make the best print.

Background

"The cyanotype process was invented in 1842 by Sir John Herschel, after he had first discovered the photosensitivity of ferric (iron +3) salts. In this process, a suitable (both chemically and physically) sheet of paper is made sensitive to high energy ultra violet (UV) light by coating it with a solution of ferric ammonium citrate and potassium ferricyanide. Exposure to UV light reduces a portion of the ferric salt to the ferrous (iron +2) state, and a portion of the ferricyanide to ferrocyanide. Washing removes the soluble, unreduced (unexposed) salts, leaving behind a deep blue and white image. The image intensifies upon drying as ferrous ferrocyanide is slowly oxidized to a deep blue color that results from a mixture of ferric ferrocyanide and ferric ferricyanide. The oxidation can be hastened by treating the image in an oxidizing bath of either hydrogen peroxide or potassium dichromate." (Chem and Art: Cyanotypes and Van Dyke prints, Malde/Bordley p.1)

Procedure

For negatives:

Equipment: Transparency plastic, 4x5" Kodak Professional T-Max 400 ASA black and white film, permanent black marker, wax paper, glue, computer with Adobe Photoshop, scanner, laser printer, Pyro film developer, Photographer's Formulary fixer, three trays, gloves, darkroom, scissors, 4x5" view camera, tripod, light meter, black cloth, film holder, timer.

Silver Gelatin Negatives: Expose two identical images on two sheets of film. Develop each negative separately in Pyro developer, one for 11 minutes and one for 16 minutes. Fix for 1 min. 30 secs. The negative that was developed for 11 minutes is the regular, low-contrast negative, and the one developed for 16 minutes is the high contrast negative. Dry the negatives by hanging them in a dust-free environment.

Handmade Wax Paper Negative: Cut out two approximately 4x5" sheets of transparent plastic (transparency plastic will work). Cut out a sheet of wax paper about 4x5", another about 4x4 and 3/4", and so on until you have 7 sheets of wax paper. Glue the pieces of wax paper together in such a way that there is a strip one sheet thick, a strip two sheets thick, and so on. Glue the wax paper between the sheets of clear plastic. Label the thicknesses of wax paper with a permanent black marker, so that they will be white when a print is made of the negative.

Handmade Permanent Marker Negative: Cut out a sheet of clear plastic about 4x5". With a black permanent marker, make a step value scale, starting off with solid black and ending with clear. Use stipple dots to create the values. Label each level.

Digital Negative: Take a 35mm negative, and scan it using the Nikon negative and slide scanner. Scan at 1350 ppi. Using Adobe Photoshop, reduce the pixel size to 150 ppi, and the print size to approximately 4x5". Print on transparency plastic using a laser printer.

For Prints:

Equipment: solution A- 27gm ammonium iron citrate, 5gm oxalic acid; solution B- 9.0 gm potassium ferricyanide, 5gm oxalic acid, 2gm ammonium dichromate; 3 syringes (one for each solution and one for the combined solution); 100ml flask; 1 glass coating rod; 2 strips of masking tape; 1 glass plate; 1 drying box; 1 contact printing frame; 1 UV light box; drying rack; timer; 5 sheets Beckett Cambric Text paper; 5 sheets 100% cotton watercolor paper; 5 sheets Bristol paper; 5 sheets Abaca Esparta paper; 5 sheets Crane's card stock.

Procedure: Ensure that working area is free of extraneous UV light, as that will affect the light-sensitive cyanotype solutions. Light the area only with incandescent bulbs. Mix equal parts (1.6 ml each) of solutions A and B in the 100 ml flask to make working solution. Use only one syringe for each solution to avoid cross-contamination. Mix working solution by drawing solution into syringe and squeezing it back out several times. Fill syringe with 0.4 ml of the working solution. This amount is a constant. Tape sheet of paper down to glass plate at top and bottom. Take syringe filled with working solution and draw a line across the top of the paper with solution. Quickly take glass rod and gently make 5 passes over the paper to ensure that the area is sufficiently covered. Put freshly coated paper into drying box, at 105 degrees Fahrenheit, for 10 minutes. After the sheet dries, place negative emulsion side up (for silver gelatin negatives) on glass plate of contact printing frame. Lay sheet of paper down on top of negative, so that the emulsion side of the negative touches the coated side of the paper. Place the rubber mat on top of the paper, and the back of the printing frame on top of the rubber mat. Secure the back of the printing frame. Set the contact frame glass side down into the UV box. Do not look at the light as you do so. Experiment with times until a print is made that has a good range of blues in it. Our printing time was 8 minutes. After exposing the print, remove it from the UV box. Remove the paper from the contact printing frame and rinse in a bath of 60-70 degree F water for 5 minutes. Place print face up on drying rack and dry for 2 hours.

Observations and Data

Visual Data: The first thing that a photographer would do when trying out a printing method is to test visually how well that method works. Visually, we decided that the marker negative and the low contrast silver gelatin negative worked the best. For each, there was more than one print where details and a good range of color were produced. The Crane's card stock seemed to be the best paper, since it consistently produced either the best or the second best looking image. The worst negative seemed to be the wax paper negative. On only one paper, the watercolor paper, did it even produce an image, and the range of blues was very limited. The rest of the prints were a solid mass of blue. This may have not been completely due to the negative- perhaps if we had exposed the prints for less time, they would have worked better. The worst paper seemed to be the Bristol paper, since it produced blue-green images without much detail.

Objective Data for Paper: There are many factors that influence how well a paper will work for cyanotype printing. Some of those factors are: coating, hydrophobia, pH, and paper content.

Coating: We made the coating procedure a constant, so this would not have affected our prints.

Hydrophobia: This literally means the fear of water. Hydrophobia is a measure of how well or poorly the paper absorbs water. An ideal paper for cyanotype printing should be somewhat hydrophobic, so that it does not fall apart during the rinsing process, but it should not be too hydrophobic, since very hydrophobic paper will not absorb the coating. Although we did not test this scientifically, we did notice that the Abaca Esparta paper was the most hydrophobic. The coating mixture did not absorb very well even after five passes- it pooled on the surface of the paper. This is evident in the print quality- the prints made with Abaca Esparta are rough and splotchy since they were unevenly coated. The Crane's business card stock seemed to be the best in terms of hydrophobia- it absorbed the coating smoothly and evenly, but it did not come apart in the rinse.

pH:

Paper for cyanotype printing should be as close to neutral as possible. If the paper is acidic, it will destroy some of the Prussian blue, resulting in a less rich final color. We observed this effect with the Bristol paper, which was the most acidic. The prints done on Bristol were consistently a greener blue than the other papers. Crane's card stock and Abaca Esparta produced the deepest, most pleasing blues, and they were also the papers closest to neutral pH.

Paper Content: Paper for cyanotype printing should be 98% alpha cellulose. Paper should definitely not have mixed content, as in recycled paper, since this will cause the image to look splotchy as a result of the coating being absorbed unevenly. This was apparent with the Bristol paper, our only recycled paper. Especially in the marker negative, the Bristol paper produced a splotchy print, with a greeny yellow area and a darker blue area.

 Objective Data for Negatives: Colorimeter Data:

The negatives were rated by how well they produced a positive at the constant exposure time. We tested an area on each negative with the colorimeter and then tested the exact same area on each print made with that negative. We analyzed the L reading of the L*a*b color scale to determine the effectiveness of the negatives. L is a measure of the lightness of a color: 0 is black and 100 is white. A true positive of a negative is exactly as far from 100 as the negative is from 0 for a given area.

Conclusions

The best negative was the marker negative. Its L value was 25.3. The corresponding L value of the positive should have been 74.7. Three papers: Bristol, Beckett, and Abaca Esparta, came fairly close to this value, with Abaca Esparta the closest at 73.1. It is interesting to note that this is the negative/paper combination that we used to determine our exposure time, and that we were able to make the negative into a nearly perfect positive by eye.

The worst negative was the wax paper negative. Its L value was 93.9, and the corresponding L value of the prints should have been 6.1. No prints came close to this- the closest was Crane's card stock, with an L value of 32.7. This is a difference of 26.6.

The best paper was the Crane's Card Stock. It was almost a neutral paper in pH, somewhat hydrophobic, its content was consistent, and it produced a wide range of rich shades of blue. Its L value tended to be close to the ideal L value, with an average difference of 18.6 from the ideal.

The worst paper was the Watercolor. It was acidic in pH and tended to produce more of a green-blue color than the neutral papers. Its L value was always the farthest away from the ideal L value. On average, this difference was 26.9. The watercolor paper did not make any pleasing prints.

The results that we discovered using the colorimeter were the same results that we had observed with our eyes, which means that we as photographers instinctively look for a true positive of our negatives.

The best print overall was the combination of low contrast silver negative and Crane's business card stock, as we had predicted. There was a wide range of rich, deep blues, and a lot of detail in the print. The difference between the ideal L and the actual L for the print was only 13.5. The print was smooth and pleasing.

References

Pradip Malde and Dr. John Bordley for historical information, Mike Ware for factors affecting paper and ideal paper type.

Ginny Waymouth, Lauren Dossey, Jessica Moore