I'm mid-way through my first intaglio printing class. Mostly it has focussed on etching, burnishing, scratching et al. Me being me, I want to start printing photos at this point. Can someone summarize the pros/cons involved in using different plates and their methods (copper, polymer etc.) i.e. is one type of plate more durable than another. Also the pros and cons of different resist methods. Costs? Screening methods (i.e. aquatinting) Negative density ranges? Thx.
~m
Photogravure goes back a long way and there have been many technical approaches. When it was a common commercial practice, there was a gelatin photogravure film available which one bought and used. It's no longer around. Making one's own film is largely antiquated by modern approaches (though I would love to see a period step-by-step description for making film). So when we talk about doing photogravure, we're usually talking about some modern version and approach.
I tend to think that any transference of a photographic image to a plate, then printed as an intaglio print with an etching press, is "photogravure". But some modern techniques have been named other things by their creators, notably Keith Howard's "intaglio-type". Howard came across a Dupont film that was made for etching circuit-boards (not micro-chips but larger-scale boards). It hardens when exposed to UV (usually through an image-mask of course) and develops with mild caustic. It was called Riston. Howard developed a photogravure process around it, mounting the film on a plate and etching only the thickness of the film (not through to the copper substrate). The film is durable enough to pull an edition of up to 100 prints, which is certainly in the range of (non-steel-faced) copper and zinc. (By pulling an edition, I mean inking it with etching ink, wiping it, printing it on etching paper through a standard etching/intaglio press and getting 35-100 consistent images). Dupont repackaged it for this unexpected use under the name ImagOn. There is now an ImagOn II, with slight improvements. Howard took all this on the road and does a workshop circuit, emphasis on non-toxic intaglio methods and materials. Google him and order his book for plenty of advice.
The other dominant approach currently is Solar Plate. Sold at Graphic Chemical, Takach Press and many intaglio-supply sources, as is the ImagOn. It is a plate ready-prepared with the industrial alternative to masking film; a liquid resist solution with the same UV/developing characteristics, floated onto the plate and dried. In this case, the approach is to develop through to the copper, then etch that in a mordant and get your image really into the metal. The mask is then washed off and you have a traditional copper photogravure plate. Here's a fascinating pdf on the industrial product/process:
http://www.htp.ch/pcm.asp
Go to the home page and open "Liquid Resists..."
With this second approach, you wind up in the same place; your image is etched into an inkable surface and will produce an intaglio print in the usual manner. The Solar Plate, being copper all through, if steel-faced, would be far more durable; otherwise not a big practical difference in durability. The ImagOn gets you away from acids, but if you etch copper with ferric chloride you're not dealing with classic acids anyway. With ImagOn, you're putting the labor in so the cost per plate is less. And if the plate fails, wash it off and do it again. Once you've etched the copper of a Solar Plate, it better be good. I've not seen convincing evidence of better image quality with Solar Plate, but that argument is out there.
With both approaches, you have to calibrate your inter-positive density to the exposure source, as well as the nature of the inks/paper/wiping technique. In other words, you develop step-tablets and contrast curves like everyone else here. A gross generalization is your negative will look like it will produce very low contrast prints. But you have to start with your exposure source and go from there. Both ImageOn and Solar Plate are intended for near-ish UV so strong sunlight is good and plate-burners are great. Black lights don't work.
Screening. The process is intaglio, so you need a 'screen' pattern of some sort embedded in the image. Otherwise if you expose through a true continuous-tone inter-positive, it's all just open-bite. Not many do true aquatint anymore (well, artist-etchers do of course, but not many photogravurists), but there's no reason why not. Likely it will produce a somewhat coarser texture than you have in mind, but not if you become an expert aquatinter. Most people buy a screen printed out on film and pre-expose the plate to register a grid or dots or stochastic pattern. But it is possible to embed a pattern into the image itself and print it out on an inkjet these days. Here you find all sorts of advice and there are various ways to skin the cat. Printing red-orange as a chromatic filter. Using pigment blacks for good blockage. Clearly, this is an area that gets calibrated into your density/exposure. Dan Burkholder had a lot to say about this stuff (there's a website) but the furious pace of inkjet progress tended to obsolete concrete advice quickly.
Hope some of this helps. I'll be interested to see some more concrete advice discussed.