Paper Handling

Paper Handling

Proper paper handling is critical not only during shipment but also within the printing plant environment.

Paper must reach pressroom temperature before unwrapping to prevent curling caused by moisture gain or loss. It should remain tightly wrapped until press-ready and again after printing to prevent press sheets from developing tight wavy edges.

A hygroscope measures the moisture content of a paper pile relative to pressroom humidity. These readings help press crews determine if paper conditioning is required.

Figure 5-7 provides decision guidelines for printing sheetfed paper, assuming paper at 45% R.H.

Temperature conditioning. This process requires that paper remains wrapped until it reaches the same temperature as the pressroom where it will be used.

Some printing plants store paper directly in the pressroom, eliminating the need for temperature conditioning. However, when paper is stored in separate warehouses or storage areas, temperature differences between storage and pressroom environments make conditioning essential (Figure 5-8).

Temperature changes occur when cold paper from a warehouse or truck enters a warm pressroom, causing trouble even when paper is wrapped and sealed against humidity changes. Unwrapping cold paper causes moisture to condense on its edges, resulting in wavy-edged paper.

When paper temperature exceeds pressroom temperature upon unwrapping, the surrounding air warms and its relative humidity decreases. The paper's exposed edges lose moisture to the atmosphere and shrink, creating what is known as tight-edged paper.

Air cooling units that chill the air also dry it, creating tight edges in paper. Effective air conditioning requires control of both temperature and humidity.

Air conditioning paper is manufactured to remain flat and resist developing wavy or tight edges. A conditioned pressroom with constant relative humidity and temperature allows printers to order paper balanced to a specified relative humidity.

Most paper manufactured in the United States and Canada has a relative humidity range of 35%~50%. An air-conditioned pressroom should maintain a selected R.H. value within this range.

For high-quality, close-register printing requiring multiple press passes, paper with an R.H. 5%~8% higher than the pressroom is desirable. This paper loses moisture to the pressroom atmosphere at approximately the same rate it picks up moisture from the press, assuming controlled pressroom R.H. Minimal moisture change between successive printings facilitates tight-register work.

Paper cannot be produced to meet the R.H. requirements of pressrooms without controlled temperature and humidity. Papermakers produce papers suited to average pressroom conditions. Even in uncontrolled environments, paper should still undergo temperature conditioning.

Storage. All paper deliveries should be inspected upon arrival. Repair minor tears in wrappings or cartons, and reject skids with punctures, tears, or breaks in protective wrapping. Document damage on way bills and photograph damaged skids and cartons before removal from trucks or railroad cars. These photographs provide proof of condition upon arrival and help papermills identify causes of damage.

If wrappings must be removed for sampling or testing, bring wrapped paper to temperature balance before opening and rewrap immediately. Careful handling minimizes unloading damage.

Ideal warehouse and storage conditions minimize paper movement and rehandling from receipt until press arrival. Each movement increases the likelihood of handling damage, whether to access other skids or transport paper to the press.

As the printing industry advances toward 2026, increased automation in material handling and climate-controlled storage continues to reduce paper-related production issues. Sustainability practices also drive greater emphasis on proper paper management throughout the supply chain, minimizing waste and optimizing resource use.