Offset lithography steps
On an offset press, every minute of downtime equals money lost. Being proactive with proper press maintenance—from blankets to roller settings to dampening systems––is the key to efficiency and profitability in your pressroom.
Greg Workman, Technical Consultant/Pressroom and Bindery Supervisor, brings 34 years of industry experience to teach—both through classroom and hands-on training—tactical techniques for proper maintenance, troubleshooting, and efficiency in Extreme Offset: Troubleshoot, Control, Optimize. Here, Greg shares10 steps to achieve successful lithographic dampening:
- Give a sample of your water to your dampening solution manufacturer for analysis. This sample will provide information for selecting the correct dampening solution and alcohol substitute chemistry for your dampening system and your plant’s water characteristics.
- Discuss your printing operation with your chemical supplier. Be specific about press models, dampening systems, inks, roller washes, blanket washes, and types of paper to make sure that they are totally compatible.
- Check dampening roller pressure settings and durometer readings. This should include inking and dampening form rollers. Make sure plate-to-blanket pressure is also set properly.
- Follow the manufacturer’s mixing instructions. If the instructions recommend mixing between 3 and 8 oz. of solution with each gallon of water, start with the minimum of 3 oz. Take a pH/conductivity reading and record the information as a starting point reference.
- Run this mixture of dampening solution and monitor its printability. For example, how does the plate roll up? How does the press start up after feeder trips? Does the plate run clean and open without feeding excess amounts of dampening solution? Communicate this information back to the dampening solution manufacturer.
- Observe the scum line.Whenin perfect ink-and-water balance, an ink scum line will form on the lead edge of the plate. It will be thin and even (visually about the width of a lead pencil line) spanning from the operator’s side to the gear side of the press. Check it often. When the line disappears, the dampening water setting is too high. When the scum line thickens, the dampening water setting is too low.
- Check your dampening solution regularly. Paper coating, ink bleed, and blanket and roller cleaners can contaminate dampening solution. Take temperature, pH, and conductivity readings after every three hours of press operation. Record these readings in the press logbook. Keep the solution at the mixture you have found works best.
- the changes in pH and conductivity as the pressrun continues. When they reach a point where printing problems begin, such as plugging or scumming, the dampening solution is probably contaminated. Record your finding in the press logbook and mix a fresh batch of solution.
- Drain and clean your dampening system weekly.
- Check and service the refrigeration system on your water circulation systems regularly (after 1, 000 hours of operation). This should be performed by a qualified technician. Proper cooling of fountain solution helps to control the viscosity of the fountain solution.