Best plates for superfine type

Patrick

For fine details and clarity photopolymer plates will beat out magnesium plates hands down. But you are looking at things wrongly here. Photomechanical plates are done by professionals. Your “burning” photopolymer plates is apparently not so. Big, big difference.

Gerald
http://BielerPress.blogspot.com

How fine is superfine? I burn plates from a 1k metal halide bulb and process by hand. I tray develop camera film manually as well.

Up until this point, using Boxcar’s 94FL plate, the slightly softer one which supposedly holds better detail, I have had no problem holding .25pt detail, or .0035” lines. How detailed is detailed? How dense and crisp are your negatives? How does the rest of your plate process? Is it a crisp transfer from your negative, or are they under/overbitten?

Could be vacuum, lights, negative, wash method. You really gotta troubleshoot in platemaking, more variables than in printing perhaps.

Proper exposure and washout are essential in getting the best image from the negative, but if the detail is not sharp and well-defined in the negative, no amount of fiddling with post exposure process will make much difference.

Generally I find longer exposure necessary for holding very fine detail as it creates a better base for the lines (longer exposure tends to spread the shoulders a bit.

If properly exposed, standard washout techniques should render a good plate.

I’ve got to agree with Gerald that magnesium is not the best material for super-fine work. The metal tends to be too grainy for very fine lines, and the acid tends to produce ragged edges.

As far as PP plates go, they are about as good as you are going to get with a relatively easy process that is applicable to letterpress. If you are having difficulty with very fine lines, look at your negatives. Are you exposing emulsion to plate? or are you exposing through the substrate? This can make a big difference, especially if you are using films made for photo-offset. For the very finest work, you can’t just flip a thick negative over and call it good.

The next step is etched copper plates, which will hold VERY fine type indeed…. but when you get that fine, you really need to print them as itaglio, and not as a relief print. (Letterpress does have some limitations, just like all processes. ) Presensitized copper is available in the marketplace.

If you want the ultimate in super-fine type or micro printing then you’ll need to use etched HC Steel plates, printed as itaglio…. but that may be a bit difficult. Polishing the plates to a mirror surface, coating the steel with resist, making razor sharp negatives that run emulsion to reversed surface, and then etching without over-biting is a quite cumbersome process. It CAN be done in a small shop, but it is not worth the effort unless you are printing many thousand pieces of security paper, or something equally valuable.

I home expose and hand wash out plates all the time. Smallest type I have done that to was 5pt condensed Helvetica. Not the funnest to try and hand wash out but possible if you know your ability and set a timer. I never wash out anything larger than 5 x 7 by hand. At that point I farm out the plate to someone with the appropriate machines. But photo polymer will hold detail very well!

Type with detailed swashes in script typography and fine serifs or small counters need to be executed as Gerald said with a photopolymer platemaker. That is producing consistent work at a high quality. Making sure there is enough shoulder for the fine lines to stand onto so they don’ wash out or break off in the printing process.

Casey
Inky Lips Press

Thanks every one! Great comments and very helpful. I erperimented wth the exposure and wash out times and had great results, good crisp detail. Also found out about film density. We have changed out our film processing equipment and have some trouble with the negs. which I got a bad batch. Seems photo-poly plates are much more light sensetive than plates made for off-set and engraving.
Thanks again, Patrick

A neg with 2.0 density may work for offset plates, which have a very thin emulsion. Specs for photopolymer relief plates (relief, since offset and screen printing also use a photopolymer image layer) indicate a 3.5 or even 4.0 density. Without that density you are also exposing the non-image area.