printing type pressures

I am interested in actually how much pressure type needs to print. I might build a replica hand press one day-6 years from retirement. Reading up, apparently common presses were thought to be upwards of half a ton, authors quote a ton but I wonder how it was measured(probably for two pull presses).
Various books say that the invention of the Stanhope press increased pressure 10 fold or that the effort to obtain a similar printed result was 10 times less.Converted one pull wooden screw presses with additional leverage apparently broke them. Contemporary reconstructed common presses-we have one at Amberley Museum for example , Gutenberg presses seem to print quite well.

And as we know iron hand presses greatly increased pressure,I suspect that a level bed and platen was a huge factor to compensate for the inadequacies of wooden platens with a fine pressure point with the platen being steadied by being tied to hooks, even iron faced platens.
We understand that the area of type to be printed is proportional to platen size, and that for example the Heidelberg can print up to 44 tons pressure.

But is there a table or some kind of research that can show what pressure is “adequate” to print type (assuming it is in reasonable condition, bed and platen, press etc being set up correctly ), that would show the progressive correlation between differing areas and densities of type to be printed, for example an “A5” with little type of small point size is going to be different from one heavily packed out with large fount size, an “A3” very densely filled with say 6 pt could be different from one filled with large font but little of it. Exactly how much pressure in lds/sq inch or equivalent is “kiss impression” for example?
It is obviously different for cylinder presses. I was wanting to explore the creation of a modern hand press made with lightweight composites.

Presumably type foundries have worked out how much pressure their type can withstand before crumbling but that is different to printing them either lightly set or set in block.

Thanks very much in anticipation, I am genuinely interested to find out, admitting I am not a professional printer in the trade by any means whatsoever, I just normally work by adjusting packing and make readies etc with hand presses,using an Adana, cylinder proofing press at work for students , plus have a small treadle at home to play around with in the near future.

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Bear in mind in the handpress era, cotton paper was the norm and it was printed damp. Less pressure is needed than for printing dry.
Many of the earlier Stanhopes had to be reinforced becaause the mechanism exerted more pressure than the frame could take.

With an iron hand press you can calculate the amount of force transmitted from the hand to the type based on the compound leverage. It’s a bit more complex with the screw mechanism, and I don’t know how you calculate that. The machinery of a platen job press makes calculating the pressure even harder. There are pressure-measuring adhesive tape-based squeeze-measuring methods available for industrial use which in theory could tell you how much pressure is being applied. It definitely requires a lot more pressure to print a block of type on a dry textured paper than to print the same on the same sheet dampened.


And of course you have to remember that the pressure increases as you get closer to the deadline! :-)


Hand-press printers use bearers positioned in the corners of the type-bed, or elsewhere in a form that is unevenly distributed, to prevent too much pressure being applied to a form. This practice is quite old, and is mentioned in Moxon (1683-84). The older common presses were not as accurate in distributing pressure, but as they developed over time a point was reached that determined the overall extent of the depth of impression. Iron hand-presses have more adjustments to set the sweep of the bar so as not to crush the type, although it is still possible to do so by over-packing the tympans.

I was taught that a commercial platen press applies 450 pounds per square inch in order to print a full form. Of course the true amount of pressure can be adjusted by makeready, as some parts of a form might need more pressure than others (6 point type versus 72 point type, or line engravings versus half-tone engravings).

I’m sure there are pressure testing tools that could determine the exact pressure, but knowing the numbers won’t really help in determining the pressure needed to make a form print properly. Theory and application are different and highly variable.

Technically it takes no more pressure to print a dry sheet over a dampened sheet. The purpose of dampening a sheet is to soften the sizing in the paper, and make the paper more receptive to taking ink. The early papers were made from linen rags, which made the paper quite hard-surfaced, and ink would not easily penetrate into the paper; dampening would breakdown the hard surface that was caused by application of animal glues (sizing) to the paper during manufacturing. Today most fine papers have a high cotton content, but as the fibers are shorter than linen fibers the papers are not as strong and lack the crispness of earlier papers. Cotton papers are also much softer in relation to impression, and getting a clean print with a softer paper can sometimes be a problem.

Since the amount of pressure applied to the form is all relative to the job at hand and press being used to apply it, the numbers applied to the process would seem to be superfluous. The subject was never more than a passing conversation in any shop that I worked. Understanding the operation of pressure adjustments of each press seems to be more pressing.

well thank you for comments so far, much appreciated, hi Bob too. Very interesting about pressure measuring tape-partly the idea is to try to find how much pressure to possibly work how much causes flexing in lightweight composites, apart from the obvious that the platen (I like the spelling”plattin” in old books too) should be 100% rigid……one day would be interesting to compare all the old presses together with the same form and a variety of forms, I like the idea of the “Medhurst” type of mechanism that was also used in Stansbury presses, easier than cutting screw threads.

Jonathan…. I did a rather complete study of required printing pressures several years ago using strain gauges and several different presses, even to the point of breaking one of the Kelseys. I used the data much like you intend to do: building my own presses… which I did with excellent results.

All of my results were expressed in lbs/squ in of type area, and overall lbs of force. They are posted here in Briar Press. If you do a search, I’m sure you will find it.

wowee amazing winking cat, thank you for heads up, will look. Thinking? about previous comment, as type was used in a form with platen bearers, perhaps all that excessive pressure-enough to break presses- was actually doing was crushing them into bed and platen and ensuring your tympan, packing and paper became a whole lot thinner….hhhmmmm