One way a composing room could print a simple straight line was to use a piece of ‘brass rule’. This was simply a strip of fairly hard brass accurately machined to the same height as type – and usually pretty thin – typically 1pt or 2pt.
This material was available in almost every print shop in the land and some had very special versions e.g. 6 point thick but bevelled off for printing only a two point face for newspaper column rules. There were wavy line rules, dotted rules to produce a simple light dotted line, and rules to produce a row of small cubes effect. There was even a patented mechanical rule for use in raffle ticket books, but we'll come back to that later.
The Right Rule
You'll need to be very careful to check you've found the right sort of rule for the job. There was a sub-contracting section of the printing trade that did the job of cutting things out to shape, never printing anything themselves. These firms used a group of specialised rules which were usually steel, not quite type height, very hard and extremely sharp on their top edge.
You won't usually want these even if they're offered for free. This stuff is also commonly found set in various patterns within a piece of block mount, to make ‘cutting and creasing formes’. These too have many a problem for the amateur.
Even ordinary brass rule was made to odd heights for special purposes, so do get out your micrometer and check.
You can do terrible damage to your soft rollers if brass rule is used without care.
Avoid a layout with rule running up and down the forme layout i.e. around the rollers, and arrange it somehow so the rule or rules lay parallel to the roller axles.
Use fine emery paper to make a tiny radius on both ends of the printing face of the rules to save them from digging in to your roller covering. Or emery a trifle off the non-printing foot edge of the rule so the whole length is just a whisker below the nominal 918" of type height – an option I sometimes go for.
You can also set up your press for ‘scoring’ i.e. the crease on the spine of a cover. You used to be able to get a rounded faced rule for this and, having taken the rollers right off the machine and set up a forme, a firm impression gave a half-decent score. With this operation another piece of brass rule laid flat and stuck to the platen will take the impression and save your packing from being chewed up too much. That piece of rule gets bent, but press it as flat as you can at the jobs end and you can often use it again.
A much better score can be obtained by using two rules set parallel, only maybe a point or two apart (this gap needs to be wider in exact proportion to the thickness of the cover board you are working with). You get two 90 degree scored bends not a single 180 degree and the board takes kinder to that.
Getting back to the old trade standards, you can further improve things by organising a ‘male force’ between the two rules you have set up. Assuming you have that odd piece of brass rule stuck flat to the packing to take the impression dent, then arrange and fix (sellotape is what I use, and this is undeniably a very fiddly job) a small length of fine copper wire (probably recovered from some old electric cable) so as to exactly fall between your two rules, and finally fix, with more sellotape making sure the wire force falls nicely between the rules. This often takes me two or three goes to get it dead right.
This ‘male and female’ principle (not using the inking system at all) has other applications. You can get a metal block with an image reversed out white from a solid background, and print it in the ordinary way.
When the ink is very hard, dry feed the paper back through the press with no inkers on, now with some blotting paper as very soft packing. Thus you get the white image somewhat embossed up in relief. This kind of approach was used by the trade for a number of specialist applications, most now long forgotten.
With those two rules plus a force, you get a really professional ‘roll score’. It looks good, the cover board is less damaged, and it hinges really well.
Going back to those raffle/draw tickets, older folk may remember that the tear off perforation used to look rather odd, a double zig-zag printed pair of rules, with a good clean slot perforation in between (nowadays perforation is mostly very poorly done). That old system was called Holroyd's Patent and was a patented device for platen machine use. The printed rules came in two parts separated by strong springs, all within a thickness of about four point.
These, when fully raised, made the zig zag printing faces a little above type height and kept your rollers away from the razor sharp serrated steel perforating rule in between. At the moment of impression the rules printed and then sank slightly to allow the perforation rule to cut and then rose again before the rollers came back down again.
Lengths and Cutting
It was once the case that one could buy brass rule in single two foot lengths, Adana sold is so and so did the trade suppliers, but one also could buy a ‘fount’ of brass rule.
This came in a special type case with many narrow long divisions, quite unlike any other case lay. In there was a set of lengths all neatly and cleanly cut to proper Em lengths, just like leads should be.
That clean cutting was sometimes also enhanced by the length being stamped lightly on the side of the rule, ‘24-Em’ or whatever.
The brass used for rules is ‘half-hard’, sometimes even harder, and it was usually manufactured by engineering firms sub-contracting, and sold through the founders. It's a devil to cut, so don't blunt the blade of your precious lead-and-rule cutter trying. It's far better to score heavily both sides (a small try square is helpful) and bend to-and-fro until it fatigue breaks. Other folk may have other ideas on this!
Steel Perforation Rules
If you require true perforation, then you can get an excellent result using steel perforating rules (usually slotted to give so many cuts to the inch) but we do not recommend trying to do so whilst printing at the same time. You can place such a rule in your typeset forme, but it would cut your rollers to ribbons. A separate working is required.
Take the rollers off the press, clean and lay aside. Impose the perforating rule where you need it to fall on the job, and fix something like a three point lead with double sided tape flat onto the packing, to take its impression.
Take all the pressure off to start with and gently bring it up a little at a time until – voila! – a just-nice, clean cut is achieved. A good deal better than the rotary perforation the trade usually offers nowadays, too!
This sort of rule is still available to purchase from the trade. Beware, its very sharp and, again, a devil to cut to length. Try a hacksaw, definitely not your lead-and-rule cutter.
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