to Fine Printing
By Fred Williams
Editor-Publisher, Type & Press
Ink rollers are one of the most essential parts of the platen press. They mix the mass of ink into a thin film, transfer it from the fountain to the disc before depositing it on the typographical surface. Fine printing dictates that these "inkers" be in top condition. Problems arising from attempting to print from less than perfect rollers may be misinterpreted as troubles with ink, paper, makeready or the press itself.
Although they are more susceptible to damage, many pressmen believe composition rollers are still unrivaled for achieving high quality printing because their surface has a natural affinity for ink. Consequently compos provide the best transfer of ink. They are also tacky, exerting a strong surface suction plus being pliable enough to ink both highest and lowest surfaces without slurring.
To prevent problems, rollers should be examined systematically and periodically. To inspect, clean the roller and examine it carefully in a well-lighted area. By viewing it under a high-powered magnifying glass, a great deal can be determined about the condition of its surface.
The roller surface should appear soft and velvety smooth. It should not reflect light as from a mirrored finish. A finger rubbed lightly over the surface should encounter only a slight resistance from a tacky but not sticky surface.
The most common deficiencies of rollers follow, along with causes and cures.
GLAZING -Causes shiny spots that result in a hard brittle appearance, affecting the roller's ability to pick up and distribute the ink. Uneven distribution of ink may lead to improper drying of the ink, causing the back of the printed sheet to offset.
Glaze usually is the result of a build-up of dried gum or vehicles in the ink. Improper washups and/or frequent use of gasoline or strong caustic solutions can be the culprit. Kerosene is recommended for washing up of compo rollers. If glazing is at an advanced stage the only alternative is having the rollers replaced or recast.
The glaze, if left unchecked, may cause the composition material to crack and particles to chip off, causing "hickies." Failure to clean ends of rollers results in a build-up of dried ink, causing ends to crack.
SHRINKING - If compo rollers get cold and dry they may become tough and hard and are apt to shrink, losing their suction. This will cause the diameter of the rollers to decrease, resulting in their failure to contact the type.
Old-time pressmen, in order to make dry hard rollers print better, washed them in lye water and then rinsed them well in clear water. They were then wiped perfectly dry. Often this will make rollers take the ink much better.
SWELLING- During warm, humid days, rollers may soften and absorb too much moisture, causing their diameters to increase. The soft, oversize roller may hit the type too heavily, resulting in their damage.
Expansion roller trucks will allow the trucks to be adjusted for -changes in roller diameters or card or sheet metal strips may be fastened to tracks or tape can be wrapped around trucks to raise swollen rollers. Placing a sheet of tin behind the form will raise it to contact shrunken "inkers."
Moisture may be removed from rollers by placing them in a box with a 10 watt light bulb overnight. Careful not to over heat.
In a hot climate, it is advisable to use a fan on the rollers while running. This will prevent them from melting. Humidity and temperature are important factors in maintaining rollers in perfect condition.
SLITS - Lenthwise slits in the rollers' surface are caused when they reverse their rotation with the printed surface. Slits around the circumference may be the result of too vigorous rubbing during wash -up instead of flowing the ink away with the wash -up solution.
SCORING - Roller surfaces can be cut by sharp ends in the form such as perforating or cutting rules locked vertically in the chase. In this case rollers can be protected by using type-high bearers or bias chases. If possible use old rollers when running jobs composed of sharp rules.
SAGGING-IS usually the result of rollers being stored horizontally in a warm area for a long period of time. When not in use, rollers should be stored vertically, covered with a film of oil or vaseline.
OUT-OF-ROUND - Rollers must maintain near-to-perfect roundness in their circumference from one end to the other, as well as identical in diameter.
A roller should caliper exactly the same end to end. If a precise caliper is not available, the roller can be checked by circling it with a cloth or flexible metal measuring tape. Or it may be checked by rotating the roller across a perfectly flat surface. Any flatness will be readily discernable.
Another test is to ink up the roller on an ink slab. Then hold roller over the uninked ink disc. Gently lower it until it contacts the plate. Then raise roller and examine the band of ink deposited on the disc. It should be equally wide from one end to the other. The width of the band will depend upon the circumference of the roller.
Rollers should never be left in contact with the ink plate, type form or any solid object as they will conform almost immediately to the shape of the object they contact. Press should only be stopped with the rollers at the bottom of their stroke, below the type form.
Compo rollers are also subject to damage from insects and rodents. These pests are attracted to the ingredients of the rollers and they can ruin a new set in just one night!