Paper Shrinkage

Paper can change dimensions with a change of humidity.
The application of ink is indeed an application of a liquid onto a dry paper, but it is not the ink that causes the problem.
In areas subject to a large swing in humidity, a difference of a couple of days may cause a change in the paper dimensions.
To minimize this, attempt to keep a uniform humidity in the shop. Open the package of paper and let it adapt to the shop humidity for a couple of days. Plan to print the subsequent colors as soon after each is dry rather than days later.
Register marks are fine if very accurately placed. Learn how to register on the fly without the marks. If your plates are right, you can register the second color to the first on the press without marks.

The other problem is an issue as well. Paper stretching when printing with heavy impression.

The other problem is an issue as well. Paper stretching when printing with heavy impression.

to dnk2h

Paper changes dimension according to humidity. It is not my field, but …

At the daily newspaper we often used casts from the matrix which was used to transfer the image from flat letterpress to the cylinders used on the press, usually called a flong. We quickly found that the shrinkage of the flong in one direction was only about 60% of the shrinkage in the other direction (at right-angles to the first). We did little colour work then, so had no real problems.

I have seen the effect of humidity, which was particularly troublesome to letterpress printers who moved a couple of miles and that put them beside a large river, with large changes of humidity which affected badly the register of coloured food container labels.

Alan.

Inky is correct, paper is susceptible to both shirking and stretching. This issue is much more of a problem with offset printing where introducing water is part of the printing process.
In letterpress printing, unless you are wetting the sheets to soften them for ink reception and deep impression, (which I’ve never found necessary, uh-oh, here come the purists) water is not part of the process and the sheets should swell or shrink. However if your shop changes from warm and dry to cold and damp you are likely to have either shrinking or swelling. In offset printing where the paper wraps around a cylinder a printer is able to compensate by adjusting the packing under the blanket. This changes the circumference of the blanket on the cylinder so that he can stretch the image to meet the color of the previously printed form.
As inky says, maybe the only thing you can after the fact is either increase the humidity in your shop to have the paper stretch or take out humidity to have the paper shrink.
Last thought, paper stretches cross grain. For instance a 8 x10” grain long, will grow to 8+ x 10. A grain short sheet, say, 9 x 7, will grow to 9 x 7+. More likely than not if you sheet has changed you will see waves on the edges, again, the answer is balance the humidity, ideal for paper is about 55% RH.

TEMPERATURE + HUMIDITY …
In 1902, the first modern electrical air conditioning unit was invented by Willis Haviland Carrier in Buffalo, New York. After graduating from Cornell University, Carrier, a native of Angola, New York, found a job at the Buffalo Forge Company. While there, Carrier began experimenting with air conditioning as a way to solve an application problem for the Sackett-Wilhelms Lithographing and Publishing Company in Brooklyn, New York, and the first “air conditioner;” designed and built in Buffalo by Carrier, began working on July 17, 1902. Designed to improve manufacturing process control in a printing plant, Carrier’s invention controlled not only temperature but also humidity. Carrier used his knowledge of the heating of objects with steam and reversed the process. Instead of sending air through hot coils, he sent it through cold coils (ones filled with cold water). The air blowing over the cold coils cooled the air, and one could thereby control the amount of moisture the colder air could hold. In turn, the humidity in the room could be controlled. The low heat and humidity helped maintain consistent paper dimensions and ink alignment.

Stanilaus Pekala

Thank you for pointing me to Willis Stanilaus Carrier and how he came to devise air conditioning.

What is the best temperature and humidity for printing? It seems 55% humidity, and I have been told by a lino operator who came from Europe that they regard 25 degrees Celsius (77 degrees Fahrenheit) as the preferred temperature, best for the machinery. But whatever, paper should be allowed to “season” for a couple of days, in small stacks, before printing, so as to be stable in moisture content. But that pre-supposes that humidity and temperature will remain constant.

For personal working conditions, people who have lived in North Queensland for most of their lives prefer a temperature of 23 C if their work is moderately vigorous, and below 25 C if resting.

There is the story of a southerner visiting North Queensland who was startled to see a journalist in the air-conditioning wearing short-legged trousers, but also a cardigan (woollen woven jacket); the reason was that he would be venturing out into the summer heat, hence the short trousers, but the cardigan was necessary in the air-conditioning. Outside would have been about 30 C and the journalist moving vigorously, and inside about 21 C with the journalist sitting still.

At the afternoon daily where I worked, summer meant a temperature in the comp room of 100 F, and we sometimes needed to be quick at remaking a forme which had been returned from stereotyping for the next edition. Stereo used a hot process of moulding and drying the damp flong to become the stereo matrix. There was a water-cooled table onto which we slid these hot formes to try to cool them; the type cooled, but the slightly warped chases were still uncomfortably hot.

By the way, Carrier started working on air-conditioning, basing his ideas on what he knew about heating air which was the province of his employers; what we know in one field can sometimes be applied in another.

Alan.

Friends,
I was thinking about what I wrote last night and realized a made a mistake in my second example.
The grain short examples 9 x 7 would stretch to be 9+ x 7,
or shrink to 8++ x 7. An example of how paper stretches would be like a cigarette representing one fiber. If it got wet, it would swell and get thicker, (wider) but not longer.
Sorry if I confused anyone.
s

thank you for all your helpful insight already! I didn’t think that the fluctuations in temperature and humidity would really effect the paper that much. But in retrospect, I did complete the job over several days…most likely over different conditions since it was over 90 or 95 degrees outside (in March). Yes, that’s what a spring heat wave in Virginia feels like.

inky, can you help me understand how to register without marks? It would make me so happy if I knew how to streamline the process.

debbie

At the risk of starting another bru-ha-ha over whether this is makeready or imposition, I thought you might find this post from last year helpful with multiple color registration.
http://www.briarpress.org/32448
s

There are many possible reasons for misregister in printing, but changes in paper size due to humidity only happen across the grain of the paper because the fibers swell but do not lengthen. This becomes more noticeable as the sheet increases in size, but would not be a problem on a grain-short business card. No mention of paper size (or nature of form or kind of press) yet in this thread.
The more information you provide, the better chance of a pertinant answer. A lot of misunderstandings online are caused by, for example, Vandercook answers to Kelsey problems.

to monotype mick of some months back

Magnets from fridge doorseals sound a good idea; there are many other sources? Such as fridge magnet cards which stick on the of door of the fridge. In this country we sometimes replace fridge doorseals long before discarding the fridge itself, and anyone who advertises to fit doorseals would possibly give you old doorseals.

Some rare earth magnets are available, they are very, very powerful; don’t let any flesh get between them as they approach each other; also expensive. Also brittle.

Alan.

below were my specs:

(3/0)
paper = 110# lettra
size = A6
press = craftsmen superior
form = photopolymer on boxcar base

The design required tight registration…and maybe I’m the only one who noticed the small misalignment. I think it was only off by about 1/32” or so. Pictures of the final printed pieces (and process) to come.

I solved my registration problems a while ago. Only print one color jobs, send out the two color stuff and let someone else have the problems.

One other consideration in these days of deep impression. Depending on the stock and the design, the deep impression could distort the sheet, pulling the edges in toward the center of the design. It wouldn’t be much, but depending on the sock and the stock it could be 1/32” from one side to the other. That much out of register is really noticeable — 1/100th is easily visible. You might have to do a trial run and measure the distortion then get the plates reduced for the subsequent colors to compensate.

Bob

There was a name for the effect described , It may well have been “draw” ,where the impression pushes the stock into the packing resulting in a shrinking of the overall sheet , this occurred during a long run and got worse as the run progressed , Saucer shaped piles could result and on work utilising (in our case) brass rules there were obvious signs of this when backing up work and turn jobs .