Printers’ rollers have occupied the greatest printing minds since the early 1800s. While the rotary letterpress machine should have improved production speeds, their potential was held back by the lack of rollers: just how could ink be transferred to the forme with speed and consistency? This article looks at early rollers, composition rollers and rubber rollers.
When using the original hand presses, printers used ink balls. A wooden handle and sheepskin bag filled with horsehair formed the ink ball, and these were used in pairs. The inker could ‘mill’ the ink between the balls and then apply ink to the forme before printing. This approach was used between in invention of the press and 1790, some 340 years.
With the introduction of the rotary press, printers simply modified their existing technology and built wooden rollers with a sheepskin cover filled with horsehair. While made with some precision, they could not coat the type effectively, and left a mark on the page where the stitching in the sheepskin cover did not transfer ink.
In 1818, Robert Harrild developed the first ‘composition roller’, made of glue (from calfskins) and treacle — his development was based on the process used by the Staffordshire Potteries to add patterns to pottery. While this mixture was tacky enough to carry and transfer ink, the ingredients led to an instability of the roller. The glue gives up water in dry atmospheres and shrinks and cracks. In damper conditions, the glue takes up moisture and the roller swells. Thomas de la Rue added glycerol (US: glycerine) to that original mix. Glycerol has a tendency to absorb moisture from the air and this balanced to a degree the effects on glue to produce a more stable roller. Rollers still had to be made to suit the atmospheric conditions and seasons — so rollers were made to different recipes in different parts of the world, and depending on whether it was summer or winter.
Making Composition Rollers
Just as printers were expected to make their own inks, they were also expected to be able to cast their own rollers. Presses (like the Arab) were supplied with roller cores (the central metal bar) and moulds for the composition. Printers would routinely melt down and re-cast composition rollers. A big problem was to prevent air bubbles from sitting on the edges of the roller, and causing small marks that transferred to the inked forme.
Commercial makers of composition rollers used a gatling gun to hold multiple moulds and pour composition mixture into all of them at one time.
Using Composition Rollers
Adana recommended four sets of rollers: two pairs of rollers each for summer and winter; one for colour work (including white) and one for black. Rollers would be used for colour first and then black. Rollers should be carefully cleaned and covered before storage using oil or petroleum jelly. An appropriate mix would be 10% medical paraffin plus ‘suffers grease’ (an engineers’ jelly).
Composition Rollers Advantages and Disadvantages
Advantages of Composition Rollers
- They are the cheapest rollers to make of the major roller materials
- Ingredients can be varied to suit local conditions
- They are supplied soft (typically 15 — 20 shore) and this can roll ink to multiple levels within a forme
- They are easy to wash up
- Composition rollers have a very smooth surface that can deliver a sharp appearance on printed material
Disadvantages of Composition Rollers
- They are less stable than other rollers in different temperatures and humidity
- Cuts in the roller will spread and widen
- They cannot be made to the same accuracy as other rollers
- They occasionally swell at the end