On Coating Methods

I've tried several methods of coating cyanotype and platinum/palladium sensitizers on paper. I primarily rod coat. Starting with a small line of emulsion (say 2ml or a bit less, or 3 single bulb pull dropperfuls) in a line on one end of the paper, I smoothly draw the line with s leading wet edge across the paper. I pick up the rod, skip over the line of sensitizer and push it back.

The rod float lightly on the surface of the paper. Several passes can be made over a sturdy paper like Bergger COT 320 with no buckling or abrasion (lifting up of the paper fibers). For a paper like Weston Diploma Parchment, the paper will start to buckle on the fourth pass when working quickly. I probably tend to make one or two too many passes with the rod on this paper. COT 320 is a easier experience.

Beth Moon does beautiful platinum and palladium work using Mike Ware's method. She makes prints as large as 16 inch by 20 inch. She surprised Mark Nelson and I when she said she rod coated even the large prints. I was always thinking I had to switch to a brush to coat the larger prints beyond say 11 inch by 14 inch.

Kim Weston taught me platinum/palladium printing with a rod and the ratio method, this was my first foray into alternative printing processes. Mark Nelson is uses a "magic brush" to brush coat his palladium prints. When I worked with him that first time he kep saying "magic brush" and I was getting worried about being alone with him in his house. He finally explained that this is the term used by platinum/palladium printers for the Richeson 9010 brush. Laying a similar amount of sensitizer as in rod coating - or perhaps a bit more - you pour the sensitizer from your shot glass used to mix it onto the paper and brush smoothly and rapidly to cover the area to print spreading the emulsion uniformly. It is with a brush that people go to the "artistic brush stroke" aesthetic of alternative printing. To show the hand coating of the paper. The "artistic" part takes some practice, as the result without forethought simply looks sloppy. There is one image that I routinely brush coat paper for to echo with the overbrushing strokes the lines in the image.

Take care to avoid getting emulsion into the metal part of the handle as it can contaminate your coating. Keep your brushes clean, rinse in distilled water, shake out firmly and hang to dry. Don't leave in a jar as this will eventually screw up your brush shape.

I've used Japanese Hake brushes with some success. They are gentle on the paper and the ones I have the bristles are sewn to the wooden handle so metal contamination is impossible.

There is not much artistry in the emulsion areas of a rod coated paper beyond the exposed image area. Many people cut a sheet of rubylith to mask the area against exposure when using a film negative, or create a digital negative with a dark border to print it white.

Judy Seigel and John Dugdale are fans of the black foam, wood handled brushes you can pick up at the Home Depot or other hardware stores. I struggle with this brush. With the Weston Diploma parchment, the foam brush raises the paper fibers. Perhaps I am too rough? John swears by them, they are cheap, and you won't get depressed when you dispose of them.

I played with coating large sheets of paper with a dense white foam roller I picked up at Home Depot. Inexpensive, washable. It is easy to doubly coat nicely with the foam roller. Lays an even coat down, seems to get the sensitizer into the paper mechanically without abrading the surface as I experienced with the black foam brush.

I've never soaked paper in sensitizer - thought I came close recently with cyanotype and Arches Platine (never could eliminate the mottling in the midtones with that paper).

I'm curious about commercial coating methods for cyanotype and platinum paper. Been scouting around for some historical descriptions - nothing has leapt out at me yet.

The Epson 3800 Printer

I use the Epson 3800 printer to produce my digital negatives. There, I've said it.

So, one thing I continually bump into is there's not enough time in the day to do all the things I want to do with my photography. And I try to ask people who are working in similar areas for recommendations on equipment and technique.

I have Epson 4800 and 9800 printers, and they are fine printers indeed. I do many a digital color or black and white print with them and have been very pleased with the results. The problem I ran into with these two printers occurred when I started trying to produce digital negatives for palladium printing with high key images. A negative for a mostly white image consists of large swathes of solid ink lay down on Mitsubishi Ultra Premium Pictorico film. While studying the prints I noticed that there were uniform horizontal varying bands of light and dark (oddly the size of the print head seemingly) forming an undulating wave that was visible in the final print. I mentioned this to Mark Nelson and he replied he had seen this before and called the problem venetian blinds (putting a name to my pain). Not on all printers, and only in large, low contrast light areas of the resulting print (corresponding to areas of highest ink density in the negative). Interestingly Alain Briot mentioned that he had seen this density variation artifact in the shadow areas of some straight digital prints, but that the effect seemed transient.

This is not the same as a clogged head resulting in no ink from one nozzle and microbands appearing across the print. That requires a cleaning cycle. These are 1 - 1.5" bands varying dark to light and back again running parallel to print head travel. The effect is very subtle (but noticeable - someone else noticed it first in a print) similar to paper warped by moisture and wavy and showing shadows - except the paper is flat.

Mark mentioned in a moment of my deep despair that he had never seen this on an Epson 2200 (which I had just given to my friend Ken) - or an Epson 3800.

An Epson 3800 is a fine printer for generating digital negatives. I mentioned that already, I think. With a 17" wide carriage it can produce 16" x 20" negatives for large contact prints. One limitation of the Epson 3800 compared to the Epson 4800 is that there is no roll media support. I have to cut down the Ultra Pictorico roll material to size to feed into the printer. On the other hand, the Epson 3800 has a much smaller footprint that the Epson 4800 and can be considered a desktop printer (the Epson 4800 strains that definition). It is reasonably priced.

I use the Epson 3800 for straight digital prints also. It holds both Matte Black and Photo (Glossy) Black ink cartridges and will automatically switch between inks depending on whether you are printing glossy or matte surface paper. Ultra Pictorico is glossy. Some ink is wasted during flushing of the shared ink line so you don't want to switch inks say between each print but rather group your printing sessions if you go back and forth between media surface types.

The printer is a work horse and I'm very pleased with it. 

Another feature of the Epson 3800 is that it outputs 16 bit files rather than 8 bit files - with the right operating system and driver. While it is missing on a list of pro-imaging printers that support 16 bit operation, it is on another list and I can confirm that the MacOS X 10.5 driver has the option for 16 bit printing. Mark Nelson hopes that the support for 16 bit images will result in even smoother tonal transitions in digital negatives.

Someday maybe I'll figure out what the issue is with the 4800 and 9800 printers. I've already varied platen height, ink density, print quality (dpi), suction, orientation of the media (when cut into sheets), and colors used for the negative. For now I don't use these two printers for making digital negatives.

I have not tried to produce digital negatives on other printers besides Epson. I suspect that is in my future.

Wash out

Let's talk about washing out the Toyobo KM73 photopolymer plate.

On Jon Lybrook's recommendation I eventually purchased the Boxcar Press brush. Dianne Longley talks about any flat soft bristle brush being usable for washout. After constructing my own using taped together bristle paint brushes from Home Depot, I decided to buy the Boxcar brush. At 4" x 8", it fits neatly in the palm of my hand. The soft bristles present a flat broad washout surface to the plate. A plate washer I saw at Kala Institute during a workshop had a large flat brush with bristles about 1" long if I recall correctly.

As Jon and others have suggested, I line the bottom of a plastic tray with a 60 mil magnetic sheet to hold the steel-backed KM73 plate still during washout. I fill the tray with tap water to just near the top of the Boxcar brush as it rests against the bottom. The water is about 70 deg. F. I do not at this time worry about the temperature of the water greatly. I keep my darkroom at about 70 deg. F also.

After first exposing the plate to the positive, and then to the aquatint screen (talcing and brushing the plate before each exposure), I place the plate into the water and allow it to settle centered on the magnetic sheet.

I fire off a two minute timer - my washout for a plate about 8" x 10" is two minutes. Following Longley's suggested wash out procedure in her book Printmaking with Photopolymer Plates, I brush the plate in a circular motion, moving from one side of the plate to the other. I think I am making 3" to 4" elliptical motions with my hand during washout. I make sure to extend the brushing about two inches beyond the plate edge when starting to ensure I wash the entire plate.

I do not put much pressure on the brush. I start by letting the weight of the brush apply the pressure, and add a bit more with my hand. The brush moves across the plate easily - though you will quickly feel friction from the "etched" areas of the plate and the bristles find a hold in the depressions that will later hold the ink. After doing this several times I think that fine bristles are probably important for washing out plates made with a fine aquatint screen.

When I reach the other edge, again ensuring I brush two inches past the plate edge, if necessary I shift the brush down, and continue brushing with a circular motion, overlapping the strokes to the other end of the plate. 

If the plate is long you may repeat this motion, reversing at the edge of the plate one more time.

Jon's site mentioned keeping a stroke count to ensure a uniform wash out. In trading e-mails with him he mentioned he is a bit more relaxed about the stroke count. That said, here is a conundrum. You really want to uniformly process the plates each and every time to get consistent results. If you use different size plates (for different size prints) this becomes interesting. I have been using 8.5" x 10" plates (cut down from larger originals) during my calibration and testing. I'm not sure what I will do when I tackle larger plates. This might be the basis for the warning on the Boxcar site to only use the brush for plates up to 9" x 12".

When I reach the end of the plate I rotate the brush 90 degrees and begin brushing along the other axis of the plate. I vary the orientation of the brush to ensure lightly scrubbing the plate in a fairly random variation. Truth be told, I then rotate the brush 45 degrees and attack the plate (gently) on a diagonal axis.

And then I repeat until the two minutes are up. Note I have read many recommendations for time to wash out. The time recommended is less for relief printing, more for fine halftone work. I do not pre-soak. And I use a soft brush with gentle pressure.

I lift the plate out of the water and, using a garden hose sprayer head set to a broad spray pattern (not a jet) on the end of a hose, I wash the plate down with a fair bit of water pressure. I make several passes over the plate with the sprayer.

I let the plate drip dry for a few seconds before laying it down on a sheet of blue shop paper towel for drying.

The polymer plate is delicate at this stage. The polymer is only partially hardened. I take care to not touch the surface of the plate with my bare hands, nor scratch it with fingernails, the hard handle of the brush, or knock it into anything as I move it around. There's no repairing it once scratched.

Contact Printing Frames

Let's start at the beginning: contact printing frames. The most common piece of equipment you will come across in alternative photographic processes.

I'm only half joking about the central role that the contact printing frame plays in alternative processes. The need for this piece of equipment illustrates some fundamental points in common for various popular processes.

First, many alternative processes are only sensitive to UV light. Because of the impracticality of producing a UV enlarger, you must have a negative the size of the print you want to create - and that negative (emulsion side) must be held tightly against the sensitized material. Enter the contact printing frame.

Second, there are some practical mechanical issues in constructing a simple contact printing frame. These devices are virtually unchanged since the early days of photography - a piece a clear glass in a wooden frame (I've been told you can sometimes find antique Kodak models at flea markets being offered cheaply as oddly constructed picture frames). Typically utilizing metal springs on the back to press the negative into contact with the sensitized surface, the ability to get a uniform contact is more difficult the larger the frame - with 16" x 20" being considered the practical limit for a mechanical frame. Given the difficulty of traditionally creating large negatives for contact printing, and the difficulty in ensuring good contact mechanically between the negative and the sensitized surface, it is the case that prints tend to be of a modest size (8"x10" or 11"x14" being popular standard sizes in the past).

Third, contact printing frames typically boast a hinged split back. "Why?" you may ask. The purpose is to allow you to check the progress of the exposure by loosening half the back, folding it away and looking at the emerging print. Many alternative processes exhibit either a partial print out (as in palladium printing) or a full printing out (as in Printing Out Paper - POP).

The third point is a matter of great practicality. I bounce back and forth in conversation between the terms "alternative" and "historical" printing processes. Most of these alternative processes were also some of the earliest practical means of reproducing multiple prints from an original image.  The readily available form of UV light was of course the sun. The intensity of sunlight varies by time of day, by season, and by weather. It's a wonder that much early progress was made in England in photography given the weather I've seen there. With exposures often measured in many minutes, the progress of the printing was periodically checked by ducking indoors or into shade with the printing frame, opening up half the back, and taking a look. And then returning to complete the exposure.

Starting with cyanotypes, and a small used contact printing frame, one can enjoy the sun and explore alternative photography cheaply. 

Enough of these asides - in the next entry, let's just simply make a print.