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Halftone

hi there!
Would appreciate some info/help on halftone printing on a cylinder press using polymer plates.
Would like to hear from someone who had good results printing halftone images which settings (and software) he used to achieve the desired outcome on the image.
Also what thickness of polymer plates offers the best results?
thank you in advance :)

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I have had success printing halftone images with polymer plates. I still use Quark XPress for my work, but I’m certain you can get the same results with any software which will allow you to define the dot size and output to the printer/imagesetter.

I have used Jet Plates (Both 152SB and 94FL) in printing halftones, and found that it is best to give yourself a pretty good sized shadow dot, about 10% and about a 10% highlight dot. This worked well for me, but your exposure and development system may allow you to go to a 5% dot each way.

It is generally good to reduce the contrast slightly in the image as you tend to gain contrast through the printing process.

I produced the images at 133-line screen for printing on coated stock. If you plan to use an uncoated paper, you would have to adjust the line screen to the roughness of the stock surface. Newspapers used to use 85-line screens for rough newsprint when they were printing from letterpress plates.

If you are printing on a very rough or porous paper (like Lettra) you may need to make a flattening (planishing) impression with a solid block (with or without an ink or varnish) and then come back with the printing of the halftone.

John Henry
Cedar Creek Press

The planishing impression is really good advice for the final outcome, sort of like pre-calendering (facing) and stretching your paper for stone lithography.

amielbcn

You really should not be trying for anything but a kiss impression with a halftone. The suggestion by jhenry and Haven Press in regard to “planishing” should make up for that. This serves not only for finishing but also as a debossed look to the sheet.

Generally, thin plates have a bit more fidelity. If you go to the Boxcar site you will note they suggest a different treatment for output for the different sized plates (thicker lines, dots, etc., for the thicker plates). I have not noticed this with steel-backed plates though (Toyobo KM95 or KM152). Both seem to handle hairlines (for example) equally well.

A problem you might encounter with polyester-backed plates is that there is a tendency of the floor to buckle around solid images, including halftones, and that can cause edging and alignment problems.

Halftones require a fairly stiff ink, hard packing, very smooth paper, etc. Plus the plates have to be kept very clean, once you start over inking, you’ve lost control. When the edges of the halftone start darkening you are on the downhill slide.

One nice thing about photopolymer plates is that there is a welling effect where surface density is gathered, which works out very well for halftone printing.

Gerald

ameielbcb

This is a showing of a halftone printed with three photopolymer plates, one of which is a solid. There are four runs of differing coloration. The solid was printed first and last with a tint base. After the first solid a b/w enhanced silhouette of the photo was printed in a darker sympathetic color and the halftone, in a lighter sympathetic color, printed over that. Last was another tinted solid.

http://www.flickr.com/photos/bielerpress/150140683/

thanks for all the comprehensive information and details!
I’ll post the results as soon as I try it!