Press packing enigma, would love ideas!

Additional troubleshooting: removed all packing and rollers, and turned the press over by hand, looking for any slippage or play. Hauled on the flywheel, drive shaft, and platen at all points of cycle. Zero play whatsoever. Went around and checked every possible bolt head for snugness, again found no play.

I am only the third owner of this press so it is in really excellent shape, I’d be surprised if it were a mechanical issue.

Not questioning anyones products, but did you double check the guages with a mic? Make sure they’re at 0.958”

Absolutely valid, I triple checked with calipers, all 4 in the set are perfectly flatted .958

A little inexperienced with all the type out there, but you wanted .958? instead of .918 or .937?

Have you tried printing any other forms? The form pictured is on the larger side. I’ve always understood the standard .04 packing setup as a sort of calibrated starting point so you can make job-specific adjustments in a measured way. Standard packing should produce a kiss impression on book weight paper with no visible impression, but with solid ink coverage for a pretty average form, maybe a dozen lines of 12pt roman weight type. Larger forms tend to require more pressure, so it’s common to add additional packing. The density of your form is also a factor, the more solid a form is, the more pressure is required.

Your form is both on the larger side, and is fairly dense, so it’s not surprising to me that you’d need additional packing. What is your form made of? I’ve also found both linoleum and photopolymer to be a bit “soft” so they compress a little bit during printing which can throw off your impression settings. I’ve had better luck using softer packing with large forms, subbing out the bond sheets for 32# lettra, or even the press board for a 110# sheet. Dampening your paper can also help.

I guess what I’m saying is that there might not be anything wrong, this form just might need this much pressure. I think you should see what happens with a smaller form, just a few lines of type and go from there.

ericm, correct – if the platen height was set at type high then the form would smash into the platen on impression, or at least not leave any room for packing and paper. I’d also be worried about the roller rails. The extra .04 allows for drawsheet, and few sheets of pressboard or bond to control impression. In my experience, you would never want your platen setting to be type high.

Bowne, thanks for the thorough reply, that’s very helpful! This form was definitely very thirsty – I was adding more ink every 30-40 impressions, and it’s definitely bigger and denser than what I usually print. It is the deep relief polymer from boxcar. Did you get better results with softer packing as in you were able to use less? Or just a more favorable print?

It’s encouraging to hear this may not be unusual. My main concern is not locking up or damaging the press. It seems like I can confidently say I won’t so long as the impression stays a light kiss, regardless of the amount of packing needed. Does that track?

As a point of curiosity – do you know why it is that large forms require so much more pressure? It seems like .958 should be .958 regardless of how much surface area is using that height, if that makes sense.

Printing requires somewhere between 100-400 pounds per square inch of pressure, so the more surface area you have, the more pressure you need. For example, if you input 100lbs on a 1”x1” block you have 100psi, but if that block is 2”x2” you only get 25psi.

Bowne, just ran the second color on this print, which was just a fill for the wings/fins, and got a great impression with just under .05 of packing, so much more in line with expectations. Looks like you were spot on!

Thanks for teaching me something new! Do you have any sense of how much packing would be ‘too much’ and risk the press – would it be obvious in the impression being too hard?

It should be pretty obvious, and it’s always best to listen to your press. A 10x15 C&P can generate a lot of pressure, you can totally overload it, but the safe operating range is pretty wide. As an example, even if you are printing on 220# Lettra with a relatively deep impression, an accidental double feed (when you feed 2 sheets stuck together) shouldn’t catastrophically overload the press. Like most things, it is a spectrum, the more pressure you use, the more wear and tear you slowly put on the press, but the critical or breaking point is so extreme that you shouldn’t be anywhere close under normal operations.

A good way to sort of “feel” the impression is to turn the press over by hand. Even with impression on the heavier side, you should be able to turn the flywheel without a ton of force. It’s normal for the flywheel to feel just a bit tight while the press is under impression, but it shouldn’t jerk, and you shouldn’t have to muscle it through. Those are both signs of excessive pressure, so you can back the press off and remove some packing. This is also a good way to double check that your gauge pins are in the right place and that they are not going to smash into your boxcar base….. (speaking from experience) If you are printing with a treadle, its motion should always feel smooth and continuous. If the treadle sort of jumps or jerks when the press is under impression, the pressure is too high. It’s also normal to hear a slight “ca-chunk” when the press closes, but it shouldn’t be loud or aggressive sounding. Old C&P catalogs market their presses as able to print forms which fill up the chase, and are built on the heavier side as to “increase its capacity for squeeze and heavy work.”

It’s best to add packing and increase pressure a little bit at a time until you hit the sweet spot, the press will tell you if it’s unhappy.

This is amazingly helpful, glad my intuition was going in the right direction. Thank you very much!

Going to suggest something nobody wants to hear but: your press is OLD. You may not think so, it looks all shiny, runs quiet etc.etc. Still, it’s old and worn. The wear doesnt show up on a letterhead or business card run, it shows up with projects like this.

That .040 packing allowance is good for the general run of work, but the form you show is probably at or beyond the 25% platen coverage rule. Just about every Platen is really only good for solid coverage equaling 25% of the chase area, so your 10 x 15 can only run a 5” by 7.5” solid equivalent area.

When a massive impression is asked for, you are taking all the slack out of the press, and that adds up in a hurry. This also shows up if you run a fountain and have a heavy form—do not set your fountain ball against the top roller UNTIL it is on impression. The rollers will be higher up the ink disk that if you are running a light form, and you run the chance of damage having your rollers crash into the fountain.

You may want to reset you packing clearance down to .025 or such, just to give yourself room next time. Also oiling the press can take some of the slack out, or at least make your press happier about the matter.

Michael Seitz
Missoula, Montana

Using only bed-to-platen gauges on Gordon platens is a very post-modern idea. The bed, form, packing, stock to platen AND platen adjuatment were once all part of a pressman’s understanding. Thousandths of an inch of materials, with thousandths of a degree to be levelled for the particulars.
Miniscule yet critical, and diffrent for every form!
Some would layer packing, some adjust platen screws along with packing. I’ve done both, and more, absolutely full-chase on a 10x15. Wide-fountain and vibrator riders too needed.
Foot-brake even.