As with any printing papers, PaperTyger printing papers should be allowed to become fully acclimated to pressroom conditions before attempting to use them. PaperTyger papers are manufactured to a relative humidity of 42-50% @ 72°F / 22°C.
As relative humidity is a function of temperature, the first step is to be sure paper reaches the temperature of the pressroom before opening any packages, cartons, or skids. Use this paper conditioning chart as a guideline for how long, e.g. cold paper might need to reach the temperature inside the pressroom.
|Cubic volume of paper on a skid or in roll||Difference in Temperature of Paper and Temperature of Room in Which it is Opened (°F)|
|Hours paper should stand|
|6 cubic ft.||6||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||79||109|
|96 cubic ft.||15||2o||27||34||41||57||79||115|
Chart provided by the Graphics Arts Technical Foundation
The next step is to ensure that the pressroom conditions are in balance with the paper. If pressroom conditions are 72°F / 22°C and relative humidity is 42-50%, the product is in balance and will perform well. If, however, the relative humidity in the pressroom varies + or – 15% from these conditions there is a chance that miss registration, curl, or wrinkling could occur.
Paper needs to 'acclimate' to its environment. The greater the difference between the temperature of the paper and the room in which it's opened, the longer it takes for the paper to be temperature-conditioned.
The chart above also shows the time required to temperature-condition paper based on the volume of paper and the temperature differential.
The moisture content of paper is affected by both the drying conditions when it is made and the relative humidity of the environment in which it's used. Ideally, paper should be made with the moisture content in equilibrium with the relative humidity where it will be used. Of course, environmental conditions vary at different places and times of the year. Ideal conditions seldom occur. When paper is drier than its environment, it will pick up moisture, and when wetter it will give up moisture. If the differences are great enough, these changes in moisture level will cause dimensional changes in the paper and cause problems such as curl, warp and waviness. The optimum environmental balance for paper is 74oF / 23°C and 50% relative humidity.
Why Be Concerned About Storage?
Paper is made from cellulose fibre, an organic material. When the manufacturer presses the cellulose fibres together to form a sheet of paper the resulting material 'breathes' so it will absorb moisture in high humidity or release moisture in very dry conditions. Consequently, care must be taken in storing paper to assure that the desired properties acquired in manufacturing are maintained during storage and handling.
Paper that is closely packed on skids, in cartons or tightly wound rolls may begin to absorb moisture at the edges, which will appear wavy, while the centre portions of the paper remain dry. The paper has 'grown' at the edges by absorbing moisture, but not at the centre so that the performance characteristics of the paper are inconsistent. The result: feeding problems, registration issues, poor run ability etc.
An Ounce of Prevention
Storing paper correctly can prevent a lot of headaches.
Paper skids and rolls should not be in direct contact with concrete or damp floors. Avoid temperature extremes, i.e. heat sources such as radiators or cold sources such as exterior walls or unheated warehouses in winter. To prevent moisture from leaching into the edges, avoid storing rolls on-end on concrete floors.
Never unload paper from a truck and take it straight to the pressroom! It needs to acclimate. When skids of paper are brought into the pressroom, bands and wrapping should remain intact until the skids have been placed at the press and the paper has reached pressroom temperature. The same is true for rolls. Un-wrap the roll just prior to hanging on the roll stands. Moisture can influence the stack between press passes if it's not properly stored, causing registration problems the second time through.
Conditioning is also important for those who utilize cut-size paper. Sheets that have absorbed moisture may curl when they pass the fuser system of copiers or laser printers. If possible, locate printing and copying operations where the temperature and humidity are controlled, to prevent excess moisture absorption. Ream wrap should be removed 24 hours before the paper is loaded into the copier or printer.
PaperTyger Paper Product Storage Instructions
The following are recommended for product storage:
- Keep products dry at all times. If a product is received wet or the packaging shows evidence of moisture exposure, contact PaperTyger customer service immediately.
- Do not store boxes or rolls of a product on a concrete floor or directly against a concrete wall.
- Keep the product on a pallet, rack or shelf.
- Do not store product where water can be splashed onto the material and its packaging.
- Do not store in a room that is steam cleaned or reaches high humidity levels.
- Sheets: At all times when not in use keep the sheets covered or wrapped.
- Rolls: Rolls should be stored wrappedas received until ready for use.
- PaperTyger Products need to “acclimate” to the environment just like stock rolls of paper.
- The optimum environmental balance for paper is 72°F / 22°C and 50% Relative Humidity (RH).
- Sheets and Rolls of PaperTyger material should be stored in shipping wrap (as received) until use.
The above-recommended storage instructions will increase the effectiveness and shelf-life of PaperTyger products. Storage is a critical component of material use. If there are any questions pertaining to the storage of PaperTyger materials, please do not hesitate to contact our customer service manager or quality manager.