New to digital letterpress

Diogrwydd,

Go to the link below and register. This is the premier website for all things photopolymer.

http://groups.yahoo.com/group/PPLetterpress/
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Gerald Lange has an excellent book of the process of digital files/photopolymer for letterpress printing.

http://bielerpressxi.blogspot.com/2006/07/printing-digital-type-on-hand-...

Casey
Inky Lips Letterpress

There are two veins of DIY film prep I’m aware of, and to begin, make sure you understand how the professional method works.

I’m no expert, but with an imagesetter and film processor, the photographic process is used to interpret digital information and expose silver-film. If I understand correctly, this process is a bit more precise, but basically the exact same as black and white photography, except from a digital file and not the enlargement of a negative. The silver film is exposed (with the imagesetter) and developped by the film processor much like a photographic print. The end result is film clear in some parts and very dark in others.

So, the two veins of DIY film prep I know of are:

(1) Using computer printers to print film.
(2) Developing film by hand in a dark room with photo chemicals.

I don’t know much about (2) and suspect it requires a bit more skill and expertise than (1). I have done extensive research into laser and inkjet film production and here are my findings:

Laser film:
Laser printers are cheaper than inkjet, as is toner. Tabloid sized laser printers are easy to find, and most come with Adobe PostScript interpretation on-board, this means you can process halftones professionally without the use of third party technology. PostScript is the industry-standard language for interpreting halftone shape, angle, frequency as well as compensation for dot-gain or loss.

Laser printers are ultimately not an option. They use heat to fuse toner to the film which shrinks the film. This makes registration very difficult. The toner deposit is not very dark, making exposure difficult. Aerosol “toner enhancers” are available and do help. If you have very simple line art you need to make into a PPP (I would say no line work narrower than 4pt) you could perhaps get by with two sheets of clear film, printed laser, with toner-enhancer, doubled on top of each other. This could be done with none of your own equipment, at Kinkos, for example.

Inkjet is trickier but works. Here are the reasons an off-the-shelf printer will not work for you and how to get around them:

Inkjet printers are not designed to do this, they do not print a heavy deposit of ink and transparencies available from office supply stores aren’t supposed to hold lots of ink.

Inkjet printers do not come with on-board PostScript interpretation, this means no powerful halftone capabilities.

A program called a Raster Image Processor (RIP) can help you with these things. These exist for Imagesetters (they are the programs that transfer the digital image into information for the imagesetter to expose to film) and there are also companies programming RIPs for inkjet printers. The two most common I would say are AccuRIP and Wasatch SoftRIP.

Not only does an inkjet RIP allow you to use postscript interpretation to print halftone images (which aren’t used much letterpress anyway) but they can also override the printers default settings and tell it to lay down TONS of ink, making a dark film.

However, off-the-shelf transparencies won’t handle much ink, so you have to buy film specific to this use, usually from silkscreening suppliers. These are also designed for dye-based inks, and most inkjet printers come with pigment based inks, so you need to buy special ink catridges as well.

The most affordable Epson packages you can buy for this sort of stuff come with printers that can handle film 13x19” or 17x22”. I have an Epson Photo Stylus R1800 that cost me about $1000 with a rip. Negatives end up costing about $3-4 per square foot.

I am looking to upgrade to a 17x22” printer soon and it will probably cost me about $3500 with a set of ink and film.

For $3500 you could probably find an old imagesetter and film processor used, and these output film for about $1 per square foot, but what turns me off these is that you have to spend at least $60 per month on chemistry to be able to run film (the developper goes bad) and they are trickier to calibrate. If you are saving $2 per square foot on film, I suppose that $60 per month will pay for itself if you are running 30 square feet of film each month, which is about what I do, but it seems like too much hassle.

That’s what I have discovered so far. I’m not sure if $1000 is within your price range but I’ve been running my R1800 for three years now printing film positives for silkscreening and negatives for offset lithography and photopolymer and it’s served me very well. Feel free to ask questions if I can clarify anything.

Paul

There’s an option for laser printers called Autotype Delta Laser film which is a paper that won’t shrink due to heat and will have the required density for silkscreen exposure. But it seems like most people use inkjet printers with special rips for silkscreen.

Is the resolution of inkjet printing good enough for high quality letterpress plate-making? That would be my worry. There are other laser-printer based filmsetting systems, like Xante Platemakers, for lower cost alternatives that may be able to create film with a sharper image than inkjet.

Epson Photo Stylus printers are generally 1440 dpi if I recall correctly. Imagesetters I believe run closer to 3000 dpi.

Silkscreen stencils are also photopolymer, lots of similar technology. However, silkscreen stencils need to be much less hard to print than letterpress plates, mostly because of thickness I believe. I can expose a screen with my silkscreen unit to a solid step 7 on a Stouffer step-wedge test (which is what silkscreening emulsion needs to expose to) in about 20 minutes. A photopolymer plate needs to reach a hardness of 18 to print correctly, and as it is so much thicker than a silkscreen stencil, it does not even reach 7 on the scale after 20 minutes.

All this to say: silkscreen film needs be much less opaque than PPP. You need to expose the plate to so much more light that the small amount of light that gets through the dark areas harden the rest of the plate, and once the areas that are not supposed to wash out are hard enough, the entirety of the plate will not wash out.

I above said that I use my printer for silkscreen, letterpress and offset imaging. To clarify: the letterpress photopolymer negatives need to be much denser than the silkscreen positives and they are printed accordingly.

thanks all for the responses.

I’m now thinking of purchasing an imagesetter, has anyone here tried developing the film by hand afterward? I see purchasing a processor as well as being excessive, as i could mix developer and fixer in more economical batches by hand. I don’t know if there are significant disadvantages to this? What does everyone think?

When you open a bottle of developer it starts going bed, it only lasts a short while, unless you are shooting a bunch of negatives you will find out that the cost of the developer will be excessive. I send my negatives out, much cheeper. Dick g.

If you mix the developer in tray-sized amounts, dumping that tray after you are finished with a run, the original developer can be preserved by laying on a blanket of nitrogen to preserve it from oxygen in the air with which it reacts. Nitrogen is available in small containers for just such use, and will extend the life of the unmixed developer solutions quite a bit. Check with some of the online (or local) hobby photography vendors.

Vials are available into which you can put the developer as well. find a size which gives you a good mix for a tray, and fill the bottles to the top with the chemical, not allowing any room for air. This also will extend the life and you won’t have to measure each time you use. The fixer is not as sensitive to oxidation and one batch can last in the bottle for quite some time. You will know that it is exhausted when it no longer clears the film in a given time.

With sources drying up for amateur photographic materials, photographers need to develop more conservative techniques.

I keep developer in an accordion bottle available from any photo supply house. You can squeeze all the air out, reducing oxidation. But any film run through an image setter will be rapid access type, and these materials need a heated bath for consistant results. Others have had better luck tray-developing them than I have (using only the Kodak 2000 line), since all I get with camera exposures are thin negs (2-2.5 density) with pinholes, unsuited to photopolymer; that is exposure for detail. You can opaque and dupe those for a usably dense negative.

I’ve found that a tradtional darkroom is easier to maintain and cheaper to operate than the newer processors. I’ve got an old vertical camera, and a set of trays that I’ve used for years…… and they work like a charm.

I keep my mixed developer concentrates in small bottles…. and simply mix up just enough for a day’s session. This avoids having to waste a lot of developer. Done this way, it’s a lot less wasteful than mixing up a tankful in a processor.

I must admit that I don’t treat my fixer well at all….. oftentimes leaving it in the tray for days, and adding a little water to redisolve any crystals. As long as it clears the negative, then it’s OK.

As far as imagesetters go: I hate ‘em. For letterpress useage, you don’t need their high resolution and cost. I use a cheaper Brother Lazer Printer on glossy stock to produce high quality line copy….. and then shoot that copy with my camera to produce a negative. (yeah…. it’s mostly old school line-art technology, I know. but it does work well.) If I want to reproduce VERY fine details, I produce a 2x or even a 3x original, and then shrink it with the camera.

About density….. I’ve never had a density problem with traditional film negatives. If I’ve had pinholes, they are typically caused by one of these things: 1. dirt / dust on my glass, lens or film 2. low temps in my developer or 3. exhausted developer.

Parallel Imp….. if your details are filling in prior to achieivng a dense enough negative with Kodak line film, check your focus VERY carefully. If it is even a little off, the details will be the first to suffer…. and will go away if you try to fully develop the negative. I had this problem once while reproducing some fine engravings. The OTHER thing to check is vibration. Even a slight vibration transmitted to the camera will cause the problem you are describing.

I will have to look into a camera/darkroom set-up like yours, Winking Cat. I have the opportunity to take an old camera for free—I’ll see if I can get it working and maybe have some questions for you soon.

Paul

WC, I was referring to rapid access film (since all imagesetter films are processed rapid-access), which Kodak was selling under the Camera 2000 and Contact 2000 names. These are what Kodak promoted as replacments for the excellent, but discontinued UltraTec hybrid films. What I generally use now is Pressline HD film, not quite as good as UltraTec, though it also uses a long-lived single solution developer, and it gives a good dense negative. I stopped using regular lith film and A + B developer when UltraTec came out, because it was so good.
Some of the camera negs I shoot are of difficult subjects, artwork in pencil or blue ballpoint, things that drop out if shot to a normal exposure or without filters. This is where with rapid acess material, the exposure to hold detail would result in a thin pinholed neg that needed to be duped. Anyway, for use with relief photopolymer, duping gives the right orientation without shooting through the back of the film, another complication affecting focus, exposure and development. If all I was shooting was a repro in 72 pt Helvetica bold, I could expose and develop to a 4.0 without problems even with rapid acess.

I should add that rapid access processing is supposed to happen at a higher temperature than regular tray developing. Lith and hybrid films are good at 68 or 70 degrees, but rapid access needs a hotter temperature. So you need a water jacket, heating mat or other means of temperature control to get better results from rapid access processing in the tray. That’s why I got thin RA negs.