photopolymer plate considerations

In a recent thread regarding Conversation Tree Press, member Pendrainllwyn rightly noted that the discussion had veered off-topic. I apologize for contributing to that muddle by responding to comments regarding irregularities found in a specific book.

Subsequently, AstulTheShepherd highlighted an issue that, in my view, likely stems from an imbalance in the plate wash-out mechanism. When one side of a plate is washed more than others, it results in a thinning of the relief surface, which weakens serifs and the hairline strokes of letterforms. While insufficient ultraviolet exposure in those areas is possible, my experience suggests the former is the more likely culprit.

For those unfamiliar with the process, photopolymer plates are made of a water-soluble UV sensitive material. In their raw form, they are placed in a vacuum frame in contact with a high-contrast film negative and exposed to ultraviolet light. The plates are then developed in a tap-water bath using a large, flat brush. The unexposed portions dissolve, while the exposed areas—the type or imagery—are hardened in a low-temperature oven. The result is a thin relief plate which is mounted on a solid base—most often aluminum or, in my shop, a ceramic magnetic material—to bring the combination to the (US) standard type height of .918".

Because this process is inherently abrasive, the platen suspending the plates must remain perfectly parallel to the brushes to avoid washing out fine details. While not as arcane as hot metal typecasting or photoengraving, it still requires strict adherence to the fundamentals.

I share this because it is possible that some members may be interested in the "modern" methods used to produce the books they collect. Unlike printing from metal type, which boasts a glorious history of nearly six centuries, the use of digital type rendered into photopolymer plates is a recent practice—spanning roughly four decades by my accounting. It is worth noting that photopolymer was developed for the commercial packaging industry (boxes, cans, and the like) rather than fine press work. Consequently, there are few commonalities informed by long historical tradition; instead, each printer must adapt the technology to their own needs and limitations.

Anything I say on the topic is based solely on my own experience and opinion. Your mileage (or that of your preferred printer) may vary. That said, if anyone has specific queries about the use of these plates, I am happy to address them either on-list or off.

>1 letterpressdotcom: thanks for posting this. It was really helpful.

Why might one choose ceramic over aluminum? Why magnetic?

It's also worth noting that photopolymer has not only had a huge impact in relief printing over the past few decades, but in intaglio printing as well! I've heard that many, if not most, photogravure printers now use polymer rather than (traditional) copper plates. You can achieve incredible detail in polymer. For example, this image was hand-inked and pulled from a polymer plate.

>1 letterpressdotcom: A few questions Bradley:

1. Do you moisten polymer before printing with it?

2. Do the plates break down after a certain number of impressions?

3. Do the plates last? Could you print from a polymer plate you made, say, five years ago, if it had just been sitting in a drawer?

4. Assuming a perfect fidelity source print and digitization process, do you think polymer could exactly replicate a wood engraving?

5. Biggest disadvantage of printing with polymer over metal?

It's whether there is that qualitative difference to older methods or if it's the skill in its application which makes the difference?

>4 grifgon: Griffin 😂 You know well that a plate of a print of a wood engraving will never come close to printing from the block! The only process that has historically come close is wax electrotyping of the original block and even that wasn’t the same.

Can the plate be recycled?

>2 abgreens: Polymer plates come in either film (adhesive) backed or steel backed form. The adhesive plates mount on an aluminum base and the steel backed plates snap to a magnetic base. I have always used the steel backed plates and have structured my business around them, so I can't speak to the benefits or drawbacks of the adhesive flavor. I've used the same two 10 x 16 ceramic magnetic bases (manufactured by Bunting Magnetics) since 1988, and 37 years later they are still going strong. I also use a magnetic base made by Pat Reagh that he has dubbed "PatMag" which is an aluminum base with a thin layer of bonded magnetic material on top (a bit like the signage on the side of automobiles). It is not as strong as the Bunting base, and larger images tend to sink into the softer material, but it is good for full pages of type, such as a four page sheet in a 6 x 9 format, where the pressure is spread out over a large area.

>6 ChestnutPress: I've heard several printmakers disagree! Curious what Bradley thinks, given his experience.

>4 grifgon:
1. No. They are water soluble and there is no benefit that I know of for moistening a plate prior to printing. This might be a problem if one is printing with dampened paper, in that the plate might degrade over the course of a press run, but I have never attempted that. I prefer to use handmade paper and hand set type when printing on a handpress, and machine-made paper with machine composition (whether monotype, linotype, or polymer) when printing on a machine press. But I think there are hand press printers who do use polymer plates, and I would like to hear their experience and learn from it.

2 & 3. The plates will last for thousands, tens of thousands (maybe hundreds of thousands) of impressions without wearing down. I have several commercial clients who use the same plates over time, and I just pop them in the oven of the platemaker for maybe 15 minutes to bake out any humidity that might have softened the polymer (Austin, Texas, can get very humid). I still have the most of the plates for a folio Bible that I printed some 30 years ago, and they could probably go back on press for a second printing (by someone else!)

4. I agree that printing from a repro proof of a wood (or Resingrave) engraving is no substitute for printing from the original.

5. Maybe the single biggest disadvantage of printing from plates (of any kind) is that there is little or no room for making changes or adjustments while on press. Sometimes you see letter or word spacing that could be better, or any number of things really, that you simply can't do anything about without pulling the plate and making a new one, which is an expensive proposition requiring new film, new plate, and new set-up. An egregious error might necessitate the expense of a couple hundred dollars, but clumsy letter spacing or a broken serif will slide. In such a situation the press operator becomes a machine minder rather than an artisan fully engaged with the typography of the book. Been there, done that.

>7 SuttonHooPress: Sure. But you'll just get scrap price for them. I recently cleared out a couple of decades worth of plates and received maybe $60 for the effort.

>10 letterpressdotcom: This is all fascinating Bradley, thank you!

I've printed twice on dampened paper from polymer, and I didn't notice any softening of the polymer. Though the runs were like 100 impressions.

As you said, it's interesting how each practice is so different. I recently spoke with a printer who always dampens polymer. ¯⁠\⁠_⁠(⁠ツ⁠)⁠_⁠/⁠¯

>9 grifgon: While you can get decent results you simply don’t stand a chance of getting the finer points and details in an original wood engraving block from a scan of a print made into a plate. There are two stages of separation involved that, while one might argue are minimal, are still going to affect the outcome. It’s true that it’s not really an issue for chunkier artwork such as woodcuts and linocuts, but for the incredible delicacies of a finely detailed wood engraving it is a problem.

>13 ChestnutPress: The degrees of separation are an issue, for sure. I'm curious however whether that's the only issue. I'm told that polymer can hold as much detail as wood or metal. It certainly can as an intaglio surface – that's well established. But as a relief surface? Bradley what do you think?

Now, this is the kind of a discussion I can really groove on. Don't stop now!

>5 LT79-1: Really curious for Bradley's response to this.

My two cents is that polymer is easier than metal. So it lowers the barrier to entry. This means that you're going to get a lot of bad work from polymer, because you have a lot of amateurs using it. Bad typesetting. Bad printing. But it also allows for absolutely masterful work – like that done by Foolscap Press, Russell Maret, or Grapho Editions. So I'd say it's all about the maker.

>14 grifgon: Oh, polymer can DEFINITELY hold ridiculous amounts of detail. I absolutely agree with that

>16 grifgon: This means that you're going to get a lot of bad work from polymer, because you have a lot of amateurs using it.

Cue Beowulf in Comic Sans with Wingdings ornaments.

>18 Shadekeep: If I hear a word against Wingdings I'll fight you! 🤜🤜

>19 grifgon: №™ₑ ☺♫♥

For people on the sidelines interested in printing with polymer plates, or just learning more about the process, see Gerald Lange's book Printing Digital Type on the hand-operated flatbed cylinder press. Gerald was the long-time proprietor of the Bieler Press. There were five editions. https://bielerpress.blogspot.com/

If I recall correctly, most of Heavenly Monkey's work is done with polymer plates, too.

The irony, of course, with the barrier to entry with polymer plates is that adhesive backed or steel backed, the base itself is going to be an eyewatering startup cost for most. Oh, you thought you only needed to spend a few thousand to get your press in your basement? How about another 1k+ to print something the size of a normal book.

We bought our Bunting bases in the late 80's and they were around $1000 each back then. So yeah, not cheap. I tried, unsuccessfully, to find the same product or something similar. AI suggests contacting Bunting directly for a custom quote ($$!!) , and also mentioned PatMag. I have heard of people using milled aluminum as an alternative to the pricier Boxcar base, which has a helpful, though not absolutely necessary, grid screened on the top. But the cost of outfitting a shop from scratch with metal type would be even more daunting. Those of us with "legacy" shops are so very fortunate to have assembled this stuff back in the day....

>23 letterpressdotcom: I know a guy who recently paid $4,000 for a custom milled bas to fit his press bed perfectly..... with a centimeter grid engraved on it.....

Oops.....

>24 grifgon: what are your thoughts on using magnetic rubber sheeting glued to plywood for the base? At this point I can’t really justify the expense of buying a large Bunting base.

>25 Another_Bibliomane: In my opinion it depends on the kind of printing you are doing and the kind of press you are working with. 3/4” plywood, even the cabinet grade Baltic birch, has more variation in its thickness than milled aluminum. If you require precise control over inking and impression — fine typography or bookwork for example — you might find a plywood base unsuitable. Also, plywood is more compressible than milled aluminum, so if you are working with a cylinder press like a Vandercook all of that pressure comes to bear in a small band and an uneven base might rock up & down, even if locked firmly into place. One of the reasons we became interested in polymer plates back in the late 80s was because our local photoengraver made crappy line cuts mounted on unpredictable plywood, so we decided to take it in-house. A bonded magnetic material has a bit of cushion in it and a metal polymer plate will sink into it on press. If you are printing, say, 60 point Helvetica Black the surface of the type can sink into the magnetic material creating a concavity and the center of the type will be lighter than the outer edges. Very frustrating. This is less of a problem with books in a normal text size, because the type is too small to sink into the material. I like the base that Pat Reagh developed, PatMag, which you can find at
https://www.ebay.com/itm/305718613694
It can still be a problem if you’re printing that pesky 60 point Helvetica Black, because the plate will still sink into the thin magnetic material, but I’ve had success with PatMag for book work.

But all of this presupposes that you are using steel-backed plates. It seems like most people these days are using the flexible adhesive backed plates on a milled aluminum base, like Boxcar Press makes. McMaster-Carr sells 3/4” aluminum plate in customizable sizes that might work for you, as I understand it has for others. An 1/8” plexiglass underlay will bring it very close to type-high if you are using the .037 thick plating ,material (KF95 in the plastic backed plate, SB94 in the steel).

>26 letterpressdotcom: Thank you, very helpful information!

At the moment I'm mostly printing photogravures from Solar Plates but I want to expand into printing text, probably with SB94, which I've found easier to register than the plastic backed plates.