Shadowing when pressing images (rather than type)

I’m having a problem that I can’t seem to fix. I use photopolymer plates on a box car base. I run a Kluge machine, and changing packing under my tympan/adding/taking paper from behind the base doesn’t do anything. I press a lot of stationery/business cards etc., and the type looks perfect, but the problem I’m having is when there is an image on the plate, there will be a “shadow” that gets pressed on the image itself. For example, if I were pressing a 2 inch square, the color would be totally uniform except for a miniscule part of the “top” of the artwork (the edge closest to the inside of the press). If anyone knows what I’m talking about and has any advice, I would be much appreciative. Thanks!

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Ensure tympan is taut.
Use roller bearers.

what is a roller bearer?

Roller bearers are two type high strips locked into your chase to ensure that your rollers are at the proper height. A lot simpler than taping the rails. I use them all the time, especially for big blocks of color: http://joiestudio.blogspot.com/2007/10/mixing-inks-roller-bearers-and-st...

But wouldn’t that print two giant bars on your tympan? I would think after a few impressions you’d have a giant gummy mess.

Use a frisket attached to the grippers.

Thanks! Recommend a place to find roller bearers to buy? So they aren’t tape? How do the affix to the chase? Are they the same material as the rollers? Are they as easily washable? Thanks for your help!

The bearers are locked into the chase along with the rest of your forme. If you search the Briarpress archives, you’ll find lots of information on using roller bearers.

Jim Reck was good enough to tutor me on the use of roller bearers and made some roller bearers for me. I also have some 18pt and 36pt rule that also work really well.

Aside from a frisket, one can also just cut away packing so the bearers don’t print.

Here are a couple of photos of roller bearers that I use in my 8x12 C&P:

http://www.flickr.com/photos/[email protected]/2093492481/
http://www.flickr.com/photos/[email protected]/2093493113/

These are simple L shaped angle aluminum or steel with a notch cut out of each end and the ends sloped to let the rollers roll on and off easily. They are type-high.

Cutting the tympan away a bit on each side keeps the work neat. You can’t print or place gauge pins under the bearers anyway.

Back to original problem, it is called “ghosting”. The solid image is inked on the downward motion of the roller (and the roller stipped of ink where it rolled over the image), but the roller inks the image in a slightly different rotation on the return. So you get a darker strip at the edge from the still-inked portion of the roller.
Adjusting roller height, trucks, bearers may reduce the problem somewhat, as may double-rolling, but ghosting is an inherant problem with such an inking system. The only definite solution is to use a rider or distributor roller to break up the ghost image. I think some Kluges did use them, as did the C&P Craftsmen, but for ordinary platens there were third-party distributors from Triumph, Acme, etc. Lots of people are looking for them now, so good luck. Or follow Leonard Mollberg’s instructions for homemade riders:
http://www.twopiglets.com/kluge/parts/#pyramid

i have a kluge that has two rollers on “top” with a vibration bar? (or something like that?) and then two rollers on the “bottom” that hit the plate and are independent of each other. would the ghosting disappear if I removed one of those “bottom” rollers? what would the negatives be of having only one roller on the bottom? thanks for all your responses everyone.

With a working vibrator roller you should not be getting ghosting. If it isn’t a large solid, try just the top two rollers and vibrator. Don’t run a double saddle with a single roller (without dummy roller core and trucks). If the bottom rollers are two single saddles, then yes, try three rollers also.
But first make sure the roller are set properly—does your Kluge also have adjustable roller tracks? With photopolymer plates you want a light contact, maybe as little as 3/32 stripe on a roller gauge (the .918 lollipop). You can refine the setting by slowly moving the rollers over the image and “reading” what is on the roller.
Contrary to what others have said, I’d suggest that roller bearers have limited ability to raise low rollers. They DO prevent roller slurring. But packing must be cut away or they will affect impression. Raise the tracks to .918 or slightly below, and make the trucks the same diameter as the roller, whether by mechanical adjustments or by layers of hard tape etc.
The worst thing you can do is to over-expand Morgan trucks to compensate for low tracks. The result is high and low spots with shfting blind areas as you print.

Pressman 1000:

If you could run the vibrator roller on the lower two form rollers, it might be better as they are the last two rollers to ink the form prior to impression, and have the most influence on the quality of the inking film.

Parallel Imp’s suggestion to check the roller heights is vital to quality inking. Don’t neglect it.

John Henry
Cedar Creek Press