Paper Bag Printing

Paper bags have folds and seams, so you are printing on multiple layers of paper. To compensate, I use a sheet of rubber on top of a tympan sheet. Not an offset blanket - their cloth backing make them too firm.

Increase packing gradually until you get a good image. Too much pressure will result in torn edges in the image area of the bag.

And use a die or a polymer plate. This is not good for metal type.

To compensate for the seams you allow for the different heights in your make ready. You take a print on your make ready sheet, mark where the seams are and what thickness they are and then build up the thin areas so when the bag is printed every part of the surface (bag + underlay) is even. You use the same method on similar items such as envelopes.

As Sharecropper Press suggests use a plate not your type.

I print string handled bags on a treadle platen and ensure the plate is not too close to the string as you sometimes get variation in position.

If you intend to print simple glued paper bags you have to separate the bags individually as the bags may have stuck together from gluing, from cutting the top edge or if supplied on a string from the hole punch.

Thanks for the feed back. We will see how this works out. I like the rubber blanket Idea. I have a lot of old press blankets I can strip the backing of off and give it a try

If you’re printing on quality bags the method platenprinter described is the proper way to setup. I failed to mention that I print on lunch bags. The image area has 4 layers on the sides, 3 layers at the center seam and 2 layers in between. And the folds and seam moves around so the proper way won’t work.

My experience with removing the backing from rubber blankets is the rubber is too thin. I buy red butyl rubber at the hardware store.

Good luck.

We are printing retail paper sacks. I have packed out printing press blankets to print envelopes for many years so all the ideas make great sense and help us to solve what we thought was going to be the issues.

It’s been years ago, but we used a rubber plate to print on some bags. Little or no makeready, and the bags came out great. I have no idea what type of rubber, or where we got it. Handfed on a C&P.

Only one worry, the reputational damage. In my working days in central London, if one wanted to belittle another printer, one used to say they were a printer of winkle bags.
Winkles, you know the small marine mollusc people used to eat - with a pin. Bought in very small paper bags, dreadfully printed. ”A winkle bag shop.”

Another winkle bag! 2 color, hand fed on old model NA Kluge with foil and hot plate add on.

Just checking Western. Did you print the bag order and how did they look?

Mint Condition.JPG

We printed a foil label on black stock. We tried running the bags but the handles were a problem.

Sorry to hear that. Did the handles extend down into the bag where the image needed to go or something else?

Ugh, bags :)
Every year we print a job of 4-5000 ~~6”x12” handled bags.

The method so far-
back off the platen but keep it level,
use a softer poly plate,
forget about the usual tympan,
use a soft rubber sheet for packing,
make reg. “pins” out of strips of wood or soda cans (and make sure they clear the furniture).

The packing most recently used is some soft red 1/4” gasket material glued to a sheet magnet which keeps it in place (tape won’t stick to this rubber, both from McMaster). It’s not much larger than the impression and that leaves lots of rooms for the reg. “pins”. We let a fair amount of “crash” happen but the packing, and to a lesser extent the plate, take up the excess. Seems to work and we get a decent impression without embossing.

My main suggestions are that trying to dodge handles is possible but probably not worth the time and to measure the bags, count the thicknesses*, and calculate how much packing is needed in the different areas (then decide whether/how much to back off the platen). Use a soft packing to make the make-ready less fussy.

*kraft paper can be 20-30mils thick, this eats up the usual 50-60mil allowance on a letterpress

Beware that uncoated kraft paper is right thirsty stuff, if you don’t have an ink fountain be prepared to add ink every 40-50 bags.

z!

zbang, is it safe to assume you’re hand feeding on a C&P?

…almost…
hand feeding a Challenge Gordon.
(Depending on which press, it’ll be either a foot-powered 10x15 or the motorized 14x20.)

Bruce - We are using a 10 x 15 windmill and test feeding with the rope/ string handles did not go well. We never even tried to print, we could tell the rope handles would be an issue and stopped at that point. They got hung up in a number of spots and we felt this would not be a simple task.

Yes, Any kind of handle will probably be an issue with an automatic feed system and the loose string handles are tough even to hand feed since they can flop around and ruin the make ready and the plate. Also, ink doesn’t dry well on many of the paper types that those bags are made from. We have a vertical pneumatic hot stamping press for those, we use a sleeve to protect the back of the bag. Slow but it makes a pretty product.