Temperature conditioning means that the paper is stored in the plant and is not unwrapped until it reaches the same temperature as the pressroom where it will be used. Required storage time depends on the size of the skid, carton, or rolls and its temperature on arrival. Do not remove or tear the wrapper during storage. Seal rips and holes with tape. To know how long paper should stand before you unwrap it, determine the following two figures and consult the chart.
FIRST: Determine the difference in the paper's temperature and the temperature of the room where it will be unwrapped.
Cut small slit in wrapper. Insert a thermometer into pile. (When you remove it, seal slit with tape). If you can't do this, use outdoor temperature when paper arrived as the paper's temperature.
SECOND: Determine the cubic volume of skid, carton, or roll.
For cubic foot volume of paper on a skid or in a case, multiply length x width x height (in inches) and divide by 1728. For volume of roll paper in cubic feet, multiply roll diameter x roll diameter (D) (D) x roll length (all in inches) x 3.14 and divide by 6912.
When calculations for cubic feet fall between two numbers in chart, use the higher number in chart. Example: if volume is 32 cubic ft. use hours on the 48 cu. ft. line in the chart below.
Cold paper in a warm room chills the air around the pile and raises its RH. Uncovered edges of paper quickly pick up moisture. Sheet paper edges become wavy; roll paper edges become slack. Moisture condenses on very cold paper like it does on a glass of ice water. As the paper warms up, some but not all of the moisture is given off. Waviness or slackness will be reduced but will not disappear with normal conditioning.
| Cubic Volume of | Difference in Temperature of Paper and |
| Paper on Skid | Temperature of Room in which it is opened |
| In Case or in Roll | 10 | 15 | 20 | 25 | 30 | 40 | 50 | 60 |
| (Hours paper should stand) |
| 6 cubic ft. | 5 | 9 | 12 | 15 | 18 | 25 | 35 | 54 |
| 12 cubic ft. | 8 | 14 | 18 | 22 | 27 | 38 | 51 | 78 |
| 24 cubic ft. | 11 | 16 | 23 | 28 | 35 | 48 | 67 | 100 |
| 48 cubic ft. | 14 | 19 | 26 | 32 | 38 | 54 | 75 | 109 |
| 96 cubic ft. | 15 | 20 | 27 | 34 | 41 | 57 | 79 | 115 |
*Above information from Lithographic Technical Foundation
Research Progress No. 44
Paper is moistured conditioned so that it will stay flat and not develop wavy or tight edges before or during printing.
Wavy edged paper can be temporarily corrected by storage in a "hot room" (100 to 110 F) for several hours before printing. Or, place strip heaters or infra-red lamps along the sides of the feeder pile near the top to warm and shrink the edges. Don't over-dry and produce tight edges. On one and 2-color presses, wavy edged paper may need to be treated before each printing.
Dry or moist paper should be hung in a conditioning machine in lifts of 25 to 50 sheets depending on the paper's weight. Modern machines use blowers and humidifiers, take little space, and require only 2 to 8 hours to condition paper.
An air-conditioned pressroom helps greatly to avoid moisture troubles especially when the rest of the paper handling system is followed.
If the pressroom is not air conditioned, if register requirements are critical, and if either the RH or temperature may change between printings, piles of paper must be protected. Cover them with a moisture-vapor proof bag or skid cover made of plastic sheeting, plastic impregnated cloth, or rubberized fabric. Covers should fit over pile and extend at least to the skid platform. Seal piles carefully so that air cannot enter.
Don't merely cover the piles with paper. Even the original asphalt liner Kraft wrapper is not satisfactory because it is impossible to prevent the leakage of air and moisture.
These reminders of good practice in handling paper in the plant will help you to avoid trouble with feeding, wrinkling, and misregister when the paper gets into the press.
*Above information from Lithographic Technical Foundation Research Progress No. 44.