The Ink Minder’s Duties [Rembrandt]
by Rob Clayton
My first job as a young employee at Rembrandt was that of ink minder or ‘ink slinger’ (a term that may have been used only at Rembrandt and Sun), a.k.a. third hand on a gravure press. The press in question was a five-unit single-width baby, to give 4+1, linked with a double-width two-unit section to give 1+1, both webs running into a variable folder. The press was manned by Bob Holden as chargehand, Nobby Clark as register-hand, and an Indian who had been with the Times of India who was minder in charge of the two double-width units.
My duties as third hand were to ensure that the 4+1 baby units were kept supplied with ink of the right viscosity, and that the doctors were prepared, installed, and maintained in good running order throughout the shift. The units were to be kept free of doctor marks, band marks, and scumming, without having to stop the press.
It was also the duty of the ink slinger to wash the surface of the cylinder at the end of the run, making sure that he did not clean the sides or any other parts, this being a task jealously guarded by the Natsopa. Supervision of the removal of the cylinders was usually shared between the register-hand and the ink slinger. It was quite usual for an experienced ink slinger to take over the register-hand’s duties if he was away from the press for a short time.
Dealing with the Ink
The presses had no ink pumps, no facilities for measuring viscosity, and used basic rectangular ink trays, yet the quality of reproduction was consistent and fully adequate for the standard of magazine colour reproduction demanded at the time. The ink slinger would be responsible for five units, four face units for colour (yellow/red/blue and the black ‘key’), and a black on the reverse that was tailored to give good strong type matter. From memory, the terms ‘cyan’ and ‘magenta’ were not used on the shop floor.
At the start of each job the chargehand would supervise the ink mixing in order to obtain the nearest possible match to the proof. From time to time it was necessary to use extender in the inks, this being a pigment-free clear ‘varnish’ that was added to the ink when the overall strength was too high and when reducing viscosity was not an option. The alternative of a highly pigmented version of the standard ink was also available, but very rarely used. For the most part the standard inks could be used without modification. The chargehand would make a note of any modifications to the standard ink and these notes would be affixed to the 50-gallon ink tanks stored near the press. The slinger was then responsible for ensuring that the inks and the doctors were maintained to provide a consistent printed image. The 50-gallon drums were supplied on small bogeys to enable them to be manoeuvred into position. Solvents were delivered in 50-gallon drums on raised galvanised bogeys.
The main solvent was tailored by the ink department to meet the needs of the work carried out at Rembrandt. Having previously worked in a gravure house where papers, films, and foils were widely used, I had plenty of experience in choosing and mixing solvents to suit the job in hand. The use of a standard solvent (except in extreme cases) made the job much easier, and was the only way that a large organization could keep some form of control over quality standards.
Without ink pumps, the ink and solvent had to be continually replenished. Ideally, the ink was run from the drum into a smaller can, and solvent added until the viscosity was just lower than the set viscosity. This ‘thin’ mix was then added to the tray whilst stirring, in order to avoid streaking.
Viscosity was judged purely by noting the way that the mixed ink dripped from the end of the mixing ‘stick’ as it was withdrawn from the can. Ford and Zahn cups [viscosity measuring cups – Ed.] were unheard of and would have meant nothing to most gravure minders. Everything was based purely on experience. The coverage of the engraved area on a cylinder not only influenced the frequency with which the ink needed to be topped up in the tray, but also affected the viscosity of the added ink/solvent mix. A cylinder with a small engraved area consumed only a small quantity of ink over a period of time. Since the evaporation of the solvent from the ink in the tray was constant regardless of ink usage, the result was that in order to maintain constant ink viscosity, virtually neat solvent had to be added from time to time. With heavy-coverage cylinders, the ink usage was high enough that very little solvent had to be added to the ink in order to maintain consistency.
During the production run it was the slinger’s job to maintain consistent print quality for his units, keeping an eye open for doctor marks on the cylinders, scumming, ink splashes, and band marks. The faults had to be rectified without halting production. There were several different ways of dealing with these problems, and it was very unusual for the press to have to be stopped for a print fault.
Band marks were marks that developed on the printing cylinder surface and were much more severe than doctor marks. I had never encountered band marks prior to joining Rembrandt. They were hard foreign matter, iron doctor filings, or chrome plating that was peeling off the cylinder and was trapped at the point of contact between the blade and the cylinder, and could cause serious damage to the cylinder surface. This hard foreign matter could be removed by applying high pressure at that point with a pointed stick like a pencil, but not a pencil itself because, if the lead were to break, it would go between the cylinder and the impression roller and ruin the cylinder.
Doctor marks were fairly straightforward to eradicate, the trick being not to let them develop properly. Doctor marks develop into fine lines, the width of the mark being equal to the width of oscillation of the doctor. The cause might be a small speck of hard foreign matter that had become trapped in one of the gravure cells, leaving part of its mass above the level of the printing cylinder surface. Over a period of time the foreign matter would abrade the doctor blade in direct relation to the number of rotations made by the cylinder, and the oscillation, speed, and track of the doctor unit. The oscillation speed slowed as the doctor reached the end of its stroke in readiness to reverse, while the cylinder surface continued rotating over the foreign matter causing greater abrasion of this part of the doctor blade, and even greater wear developing at the actual point of reversal. It was important to remove or wear down the trapped foreign matter, and the first step would be to use the pickfinder [explained in detail below – Ed.] against the surface of the cylinder. The location of the offending matter being at the central point of the doctor mark, the use of the pickfinder was usually sufficient to remove the cause. The damaged section of the blade continued to allow ink to filter through and print out the doctor lines and it was necessary to eliminate these marks in the interests of print quality. Initially, increasing pressure by pressing a finger onto the doctor for a few seconds in the area of the damage could well produce an acceptable reduction in the doctor mark strength, though this was usually only the case in the early stages of a blade mark.
Other methods were blowing a puff of air onto the cylinder face to dry the ink in the area of the mark, making sure that the ink did not dry in any of the engraved cells. A more ruthless and indeed downright dangerous practise was often necessary on the older John Woods presses, where floating doctor pressure was applied by weights rather than the rigid pressure of the lathe type system of the Sungravure presses. In order to increase pressure significantly on the doctors in the Woods presses, one method was to lay a round steel bar, about 1½” diameter and 12” long, onto the doctor blade holder/doctor blade. This was done while the press was running by carefully holding the bar with one hand and slowly and carefully leaning into the printing unit, making sure that the bar did not touch the moving web or the cylinder surface. This was particularly dangerous when the unit in question was a reverse-printing unit, because of the very restricted access. The other method of eliminating serious doctor marks or bar marks was the ‘half-crown’ method. This entailed using the circular tin discs that had been nailed to the wooden plug holding the brown kraft wrapper to the reel core. Approximately 1½ inches in diameter, the disc was bent in half and almost flattened. This was then inserted between the wiper blade and the backing blade, the lower half being between the blades and the top half being available for the printer to hold while he leaned into the unit to slide the disc over the length of the blade until it was aligned with the doctor mark. This trick never failed to eliminate the mark, but it was not good practice because the excess wear to the engraved area was substantial, so the technique was only used at the instigation of the chargehand. The risk to life and limb was substantial at a time when presses did not have guarded nips, and I doubt if management was aware of this practice. At all times the objective was to keep the press running at any cost.
During job changes, the register-hand, ink slinger, and third hand cleaned the surface of the cylinders – but not the sides of the cylinders, this being the job of Sogat (Natsopa), who were responsible for all other wash-up duties. We supervised the Sogat team as they carried out cylinder removal, inspection, wrapping, and loading onto cylinder trolleys, and removal to the cylinder storage area. The cylinders for the next job were brought back and prepared ready for insertion once the assistants had cleaned the units. While this was going on, the chargehand was cleaning, lubricating, and adjusting the folder in readiness for the next job, and the ink slinger was preparing the doctors for the run.
It was at this point that the pickfinder was pressed into use. Made individually by each printer for his own use, pickfinders were copied from existing ones made by more experienced printers. Bearing in mind that the printers had no access to tools or grinding equipment, other than their doctor files and carborundum stones, the pickfinders were carefully made and very well looked after. The principle was that a smoothly ground strip of hardened steel about 1/8” thick by about 2½” wide and 2” deep was slotted into a recess in a 2½”-wide wooden holder so that about 1” of the steel blade remained exposed. The exposed strip was laboriously hand ground using grinding stones and emery paper until the blade was absolutely straight, with a polished smooth surface. The aim was to present this flat surface under high pressure to the gravure cylinder surface, almost like a reverse doctor blade, absolutely horizontally. The smooth surface of the hardened steel blade polished the surface of the cylinder and removed the roughened ‘band’. It was a process fraught with risk, for if the blade was not presented absolutely at right angles to the cylinder surface or if the polished blade had become nicked, the cylinder could be ruined. The use of the pickfinder was a last resort; in good hands it could save the day but in the wrong hands it could be a great embarrassment.
Preparing and Setting the Doctor
The doctor blade holder comprises two flat steel plates that are clamped together and hold the steel wiper and the backing support blades. The holders must be treated and stored carefully, it being essential that they not become in any way ‘out of true.’ Cleaning is an important part of doctor preparation – mainly the removal of dried ink and metal filings from between the blades.
To prepare a used doctor for re-use, the doctor holder is clamped to the doctor bench, and the bolts holding the doctor together along its length are undone sufficiently to allow the wiping blade to be removed. Assuming that the lower part of the blade is free from ink, it is fair to assume that it is not necessary to strip down the complete assembly. The wiper blade is cleaned completely and then inspected to verify that the wiping edge has no cracks or obvious damage. (The wiper blade in the 1950s was of high-quality steel, Swedish blue steel being the favourite. The gauge of the wiper blade was between 200 and 250 microns (8 to 10 thousandths of an inch), the width was the same as the doctor holder, whilst the height was standardised for the press it was being used on: 3 to 4 inches would be the usual range.) The backing blades are positioned behind and slightly below the wiper blade, in order to support the blade against the pressure from the gravure cylinder on the run. The backing blade in contact with the wiper blade is approximately 500 microns thick (20 thou’) and is positioned about 3/8” under the wiper blade, with the second backing blade (about one millimetre in thickness), being positioned about 3/8” under the first backing blade. The reason for this configuration of the backing blades is to give a controlled springiness to the wiper blade. Not enough spring would give excess wear to the cylinder, whereas too much spring would cause the sharp edge of the wiper blade to deform, thus allowing its underside to touch the cylinder. It was usual for individual companies to standardise the specification of the blades most suitable for the work carried out on the presses in their factory.
The wiper blade is oiled prior to reinsertion into the doctor holder, a simple gauge is used to ensure that the blade height is correct, and the central bolt of the doctor holder is hand-tightened to fix the set height. The remainder of the blade is adjusted to ensure it is central, and is checked with the gauge at each end to ensure that the blade is completely horizontal to the holder. The blade is then checked to make sure no cockles are present. (Cockles are wrinkles or puckering similar to that of the edge of a large sheet of paper that has become damp. If the doctor blade is not tightened evenly on the blade holder, the uneven pressure causes the wiping part of the blade to ‘cockle.’) The alternate bolts are tightened, working from the centre out, to ensure no undue stress is put on the wiper blade. To be satisfactory, the doctor should be held in the holder without any cockles along its length, and it is now ready for finishing.
The level of the doctor blade is checked with an accurate straight edge in order to ascertain the high areas over the width, and these must be removed and a perfectly level surface with a square edge produced. A 14” x 1½” parallel smooth-cut file is used with smooth firm strokes over the full length of the blade, this being checked regularly with the straight edge. The 45-degree bevel is made using the file and a shaped wooden ‘stick’ that is usually made by the ink slinger himself from mahogany or similar wood. It is about 10” long, with a cross-section of two straight sides opposed by two curved sides. This configuration permits the side of the doctor blade facing the printer to have the file held to the curved side in such a way that it is presented to the rear side of the blade at 45 degrees. The printer draws the file/stick combination firmly over the full length of the blade several times, until a clearly defined bevel is produced, With a single sweep, the file is run flat against the side of the doctor and away from the printer, in order to remove the burrs produced by the bevelling.
The doctor is now ready for final finishing. Initially a medium carborundum stone is used to run over the bevelled section, to remove any burrs and also to give a smooth finish. This is then followed by a fine honing stone to smooth the edge and ready it for polishing with a folded pad of oiled fine ‘dust powder’ emery paper. The printer can sense the final polish to the bevelled edge as it develops during this process. The real moment of truth arrives as the edge of the thumbnail is delicately stroked over the length of the bevelled edge in order to detect any slight rough points. These rough points, if any, must be removed by further polishing.
A doctor cannot be considered ready for use unless the surface is completely free of any rough points along the entire width. All that remains is for the doctor to be carefully wiped down with a clean cloth to remove filings or abrasive powder, and the job is done. It is a point of honour that your doctors should work without any problems whatsoever when used by the next shift!
The life of a doctor blade was affected by several factors: revolutions of the printing cylinder, for instance, and cell depth. A large solid area of design where the cells are etched fairly deep would abrade the edge of the doctor much more quickly than a lightly etched pattern, and additional pressure would need to be applied in order to maintain a clean wipe. An eight- or twelve-hour run was the average lifespan before all the doctors had to be changed. The time was always chosen by the chargehand, who took into account the remaining run. The most convenient time was normally during a meal break, or even a web break. A chargehand was not expected to leave doctor changes for the next shift to carry out just after they arrived. It was good practice to do the work just before the shift changed over, handing the press over with new doctors fitted, and a spare set prepared and ready for use.