Letterpress Numbering Machine (from Flickr)
Let­ter­press Num­ber­ing Machine (from Flickr)

Anoth­er advan­tage of the let­ter­press process is that the act of impres­sion allows num­ber­ing machines to be used: the print­ing sur­face is changed each time the paper hit it.  Litho, by con­trast, must use the same, sta­t­ic plate for each impres­sion.

Cap­i­tal­is­ing on this, spe­cial­ist man­u­fac­tur­ers designed num­ber­ing machines known as ‘num­ber­ing blocks’ or ‘clocks’ by dif­fer­ent print­ers.  The prin­ci­ple is that when the impres­sion is made this push­es down a plunger which forces num­bered wheels to rotate.  These num­bers are inked and so leave a dif­fer­ent num­ber with each impres­sion.

Num­ber­ing is need­ed on many doc­u­ments: invoic­es, receipts and draw or raf­fle tick­ets being the best exam­ples.

Num­ber­ing machines are very clever pieces of equip­ment as they have to joint­ly meet the spec­i­fi­ca­tions of a num­ber­ing machine, but also a piece of the let­ter­press forme.  As such they demand a lot of care and atten­tion: they should be thor­ough­ly cleaned after use with a spe­cial­ist flu­id, then oiled with a high-qual­i­ty light machine oil and final­ly stored in a sealed box.

In terms of using them to print there are some spe­cial pre­cau­tions to take —

  • In order to pos­i­tive­ly depress the plunger, you might have to use a very hard pack­ing per­haps using a brass or lead rule to take the force of the plunger.  You should cut an out­line to receive the brass or lead from the pack­ing to assure that the end result is rough­ly the same depth as the orig­i­nal
  • If you’re using a cylin­der press (a proof­ing press, Wharfedale or a Ver­ti­cal Miele-type press) then you need to make sure that the plunger is depressed first as the cylin­der trav­els over the num­ber­ing box: this will make sure the num­bers are in the cor­rect posi­tion to receive the ink and impres­sion
  • Think care­ful­ly about print­ing first and then num­ber­ing in a sec­ond run so that re-num­ber­ing does not have to be done for the sake of a sin­gle spoilt orig­i­nal

Com­mon prob­lems, and their solu­tions are —

  • Speed
    Num­ber­ing machines are test­ed to 16,000 impres­sions per hour which is around twice the usu­al speed of the fastest let­ter­press machines.  Prob­lems with num­ber­ing machines are rarely from too high a speed; but there is some anec­do­tal evi­dence that too low a speed can cause prob­lems
  • Num­ber­ing block does not advance a num­ber
    When lock­ing the num­ber­ing machine up, care should be tak­en to make sure that the lock­up is not too tight for this will pre­vent the machine from work­ing cor­rect­ly
  • Near­by char­ac­ters are not print­ing
    If pre­fix­es are need­ed for the num­ber (for exam­ple, to num­ber books sequen­tial­ly as Book No. 1 / Invoice No. nnn) then the type in the forme should be at least two inch­es away from the num­ber­ing block.  There is a ten­den­cy for rollers to bounce on the high­er-than-type-high plunger and so not deliv­er ink on these pre­fix­es.  A rather extreme alter­na­tive is to file a piece of type to fit in place of the plunger
  • Rollers are caus­ing the num­ber­ing block to advance
    As well as rais­ing the height of the rollers, it might be pos­si­ble to cut away the por­tion of one roller that will pass over the plunger

Manual Numbering

Num­ber­ing by hand is still an option for short­er runs, and might be prefer­able where time is not in short sup­ply.  One tip is to avoid any reg­is­tra­tion marks — for exam­ple, the pre-print­ed ‘No.’ — so that the man­u­al num­ber­ing does not show as being out of reg­is­ter.

Numbering Schemes

Over time many print­ers devel­oped time­sav­ing schemes in print­ing num­bered work.  Two are described below.

For those print­ing ten-up (that is, ten num­bers to each page) it should be pos­si­ble to pre-print the last dig­it in the forme (num­bers 0 to 9) and then use ten num­ber­ing blocks in front of those num­bers which will advance on each impres­sion.  So, once the num­ber­ing blocks are at 87 that will print 870, 871, 872 to 879. across the page.  On the next pass the final dig­its remain the same but the num­ber­ing block moves on by one, so print­ing 880,881, 882 etc.

If no num­ber­ing blocks are avail­able, or larg­er types are need­ed (run­ners num­bers in a race, for exam­ple) then it’s pos­si­ble to get through twen­ty forme changes for 99 num­bers rather than 99 forme changes.

  • Set and print ten of each of the sec­ond char­ac­ter.  Place them in ten piles of 0 to 9
  • Change the forme to now have a num­ber 0 in the first posi­tion.  Take a sheet from each of the ten piles and print these.  It will gen­er­ate a 00, 0 (from the sec­ond pass) and anoth­er 0 (from the first).  Pass 9 will cre­ate 09
  • Now change the forme to have a num­ber 1 in the first posi­tion.  Using the sheets from the piles, your first print here will cre­ate a 10, 1 (from the sec­ond pass) and anoth­er 0 (from the first pass)
  • Con­tin­ue chang­ing the first num­ber until you reach 99!