A Pound of Prevention

by Frank Balentine

As climbing newsprint prices put pressure on pressmen to reduce waste while holding the line on quality, good press maintenance becomes even more crucial. The following areas should receive special attention.

Blankets

Make sure the following tasks are completed prior to installing a blanket on the press:

Check the blanket for proper thickness using a blanket gauge. The blanket should be within plus or minus .002 inches of the thickness ordered. Never allow the blanket to depress to .004 or .005 inches below the recommended thickness. If it does, replace it or add underpacking.
Document the thickness on the back of the blanket. This will prevent press crews from misreading specifications when they repack the blanket cylinder.
Make sure the blanket is square. A blanket that is not square will tend to creep apart, creating a gap between itself and the blanket on the opposing cylinder.

Metal-to-Metal Settings

It doesn't matter which type of press you have, bearer or nonbearer. Check cylinder distances regularly, preferably each time you install new blankets on the unit.

Press Rollers

The shore hardness of press rollers is measured by the Shore A durometer gauge, which rates rubber hardness from zero (soft) to 100 (hard). Maintain shore-hardness measures for ink-transfer rollers between 28 and 38, ink-form rollers between 25 and 35, and dampening-form rollers between 24 and 28. High shore-hardness readings will cause plate wear and improper distribution of ink and fountain solution to the plate.
The recommended method of setting rollers is the stripe method. It is very accurate, can be performed by a less experienced person and allows a visual check of the setting. Press manuals recommend the proper width of a roller stripe. If specifications are not available, use this rule of thumb: Set the roller 1/16 inch for every inch of roller diameter. For example, a 5-inch diameter roller should have a 5/16-inch-wide stripe.

Fountain Solution

Conductivity is a method of measuring the amount of concentrate in fountain solutions by electrical current. A good rule of thumb is to add enough concentrate to your mixing system to increase its conductivity to 1,000 micro-ohms above the reading taken at the water tap. For example, if the reading at the tap is 200 micro-ohms, add enough concentrate to bring the conductivity level to 1,200 micro-ohms.

Dampening System

A dirty dampening system will contaminate your solution, making plate cleanup difficult and good ink-to-water balance hard to achieve. Clean direct-contact dampening systems at least once a week with chlorine bleach or a similar cleanser. The recommended solution is one gallon of cleaning agent to 15 gallons of water. Clean the entire system, including the circulating tank, water pans and feed lines. Run the solution through the system for about two hours, then drain the solution and circulate fresh water through the system for another two hours. When you are sure the system is clean, refill it with a fresh mixture of concentrate and water.

High quality offset printing takes consistent and constant upkeep. Preventive maintenance programs also require time and capital. However, you will find that higher print quality, lower waste and improved morale in the pressroom are well worth the investment.

Frank Balentine is NAA's press manager. E-mail, naatech@attmail.com; phone, (703) 648-1217; fax, (703) 648-1216.