We use a windmill and pack with traditional printing press blanket packing sheets. We work with photopolymer plates. We are fine with the packing math. We are not doing a poor job, just want to refine and make it better. We are wondering if our packing is causing a spreading or expanding of our impression energy and pressure. How do you confirm the impression to the point of contact?

We work with both cotton and non cotton papers from 18pt to 40pt. We want to maximize and control our impression. We know that while we might get a deeper hit with a 16 gage copper or wood mount mag die we don’t want to go in that direction unless we have to. Since the copper and mag dies have less shoulder in effect it is easier to press into the stock, ie hit. What can I do with packing to get the best impression out of a photopolymer die. Do I want a softer packing material or a harder one or some combination. What do you pack with? Any ideas? Any pointers?

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A hard packing will give you the sharpest imaging. I use polyester (Mylar) sheets with a buried spot sheet for make-ready and a tympan paper top sheet.

To get the best impression with photopolymer, make certain you use a high durometer plate material.

John Henry
Cedar Creek Press

Thank You JHenry. I wondered about mylar, I use it when I number for packing. When you say buried spot sheet do you saying a smaller cut diameter piece under the image area? I actually did that recently but used a piece of neg film to build up an area. I had wondered about mainly packing under and around the image rather than packing the whole platen as I do now.

Hi western411,
A question if i may? What do you call traditional press blanket packing?
I have an original handbook with packing samples which comprised of ivory card and newsprint, I remember back in the 70’s Heidelberg packing being supplied ready cut to size for card and newsprint and by varying the combination you could make the packing harder or softer. I like the sound of J Henry’s suggestion of the mylar sheet, I will give it a try.

are you speaking of a spot makeready under the plate?

Frank - the blanket packing sheets are the same type we used for under packing out GTO blankets to print spec. We just got more of the True-Pack for GWJ.

Ericm - we wondered about spot make ready under the packing, so mainly pressure at and around the point of contact and thus less pressure across the rest of the platten- concentrating pressure the the printing point. I also wondered about using a sheet of mylar under the tympan as the first sheet and then using press packing under that to build the rest of the packing.

Anybody- If I used a piece of spot mylar as my first contact packing will it act like a soft counter so to speak. We wondered if we have a way to contain the the image and limit the diffusion of pressure can we get a better hit. We know we can also go to a deep etch copper 16 gage but hate to make things or more difficult or costly.

We are most likely over thinking this, but unless we ask or try wont learn anything new.

Footnote - When we pack out the platen we use full platen size sheets of packing even though we may only have a 3 x 3 image area. Is this the best, correct, braindead, rookie way of packing out the press?

Underlay, Interlay and Overlay. Underlay to adjust for imperfections in the block mount, wood was often rather wedge shaped, Iinterlay (sometimes) particularly with copper half-tones just one tissue layer maybe one thou, between the block and its mount and then the overlay, usually at least one or even two layers down in the packing, and what John Henry says about hard packing, eg mylar is exactly right, see the PATRA research by Len Boxall et al in the later 1950s early 60s. Also see just for interest ‘chalk overlays’. They were excellent, but I never thought much of the 3Ms heated sheet system. The finest craftsmen for the very best work used to cut three layer tissue overlays for half-tone work and sand-papered the edges, results: pretty damn good. eg in the UK Curwen Press (come back Wally Hart all is forgiven) and a few others in the UK like Kynoch.


By spot sheet I meant a sheet which is firmly attached (under the platen bail or front clamp on a cylinder press. Once you have a “good” print, you add your make-ready, adding cut-away “spots” of tissue which provides better impression in areas of heavier image. This prevents giving too much impression to small images which would be pressed too heavily if the overall impression was adjusted in order to get good impression on the heavy image areas.

If you can get your hands on a traditional printing book from the 1930s or 1940s, this is usually explained in great detail.

You will find that Mylar is not very compressible, so is not soft at all. I generally use Mylar (polyester) as the bulk of the packing so it doesn’t “give” during impression, providing a good, hard surface to bear against.In order to keep the polyester from “planishing” the back of the sheet (making it glossy or shiny in the impressed image areas, I use a normal top sheet (oiled tympan or just strong paper, in order to not get that shininess. The sheets used for packing a litho plate are also dense, calandered paper which also is not spongey and would be good for packing.

You will find you get the best impression in thick, soft paper if the impression depth is limited to the thickness of the paper, and is not very detectible on the reverse side. At least that is what I prefer. Others may diverge from that.

John Henry
Cedar Creek Press

Thank you for the feed back. We had never considered using spot packing. We will give it try and see if it improves our control.

Western -
Like J Henry I have always used a spot sheet from the clam shell tredal platen, heavy art platen right through to 2 rev miehles and rotary perfectors. Recently I did a 4 colour halftone image on my vertical miehle using polymer plates but produced 3 sheet overlays for each colour. For solid blocks of colour I like to use a blotting paper overlay with the edges chamfered down. When I started in print we used chalk overlays but mostly the Primaton overlay that uses a fine powder similar to thermography powder which adheres to the solid areas and was then fused to the paper with heat.

Thanks for all the feed back. It gave us some ideas we would not have thought of to try. It looks like we were already headed in the right direction but now we can fine tune or efforts.

Wow, a lot of this is over my head, but certainly deserves more attention on my part.
For the record, I always use full-size packing, otherwise, it tends to “drift”. ie, move about. When I spot makeready, I place it with a piece of scotch tape on the edge for the same reason. I don’t want it to move.

I would normally use full size also but did wonder if spot packing would change the transfer of pressure differently with a smaller area of compression. We run a lot of jobs to guides and since a lot of the paper we run is smaller sizes we are going to try creating spot packing from the bail and gripper to an area equal to our paper and or image area and see what happens. I have used spot packing and did tape it so it would not move. I used old printing negs, 1 to 3 pieces, which was an idea one of you gave us and it work great. It made it easier to get a little more hit and fine tune between packing and overall pressure trade offs.

ericm- I failed to mention we have put packing behind the base on occasion. It was one of this times when extra packing and changing pressure did not quite work so tilting the chase to meet the paper was faster. I made sure it fit under both the base and the chase edges, I was afraid I might blow out my lockup.

Lastly - thanks your help guys. I see some of the names here and have great respect for your pool of knowledge. Since I dont really know what I am going I am walking blindly into abyss of letterpress your support means more than you know.