Difficulties encountered in offset printing The following difficulties encountered in printing mainly originate in the paper in conjunction with the climate and the printing ink. Since paper and cardboard are natural materials changing their dimensions in accordance with changes in climate utmost efforts should be made to keep the climate as constant as possible. The optimum climate is in the range between 20 and 25 degrees Celsius and a relative humidity of 55 to 60%. In order to avoid troubles due to wrong climatic conditions we recommend: start multi – colour jobs that shall be printed in a single colour press with a stretching run, i.e. an idle pass of paper through the machine with printing and damaging unit being switched on. Please note that in a single – colour press with standard dampening this stretching run will result in an increase of the relative batch humidity of 3 to 4%. Symptoms Causes Corrective Measure Wrinkles in paper Paper not matured Variations in humidity during transport and in store Gripper adjustment Use after 30 days of manufacture Condition the paper Check Gripper adjustment Difficulties in register Paper size variations through moisture Pick - up and moisture loss Condition paper Paper buckles in the inking area resulting in register difficulties Large print area and paper with low grammage Use appropriate paper and less concentrated ink Sheet tail curls The printed sheet curls at the tail due to strong ink and a small break angle at the blanket Do not use concentrated ink Enlarge the blank area Sheets stick together Sheets stick together at the printed areas in the second pass Frequently aerate the sheets  Use only small piles Replace emulsified Printing ink Increase the quantity of powder Paper repels ink The ink is repelled by the paper Change the paper or varnish it Paper structure shows through in the printing subject Spots in the printed area on the wire side of the paper Print printed area twice Use less concentrated ink in the first pass Troubles in paper transport due to static electricity Wrong climatic conditions Air humidity is too low Air condition the paper and the shop Ink accumulates Ink accumulates on the blanket Use sized paper of better quality Add print oil Paper sheets cockle in the pile Air is too dry Paper piles are dry at the edges Condition the paper Paper sheets are wavy Air is too humid Condition the paper