Published: 2026-10-16 · Category: Handling
Filter paper is largely cellulose fibre and takes up moisture from the air. A change in moisture content sets off a chain: fibres swell, the pore structure shifts, stiffness drops and permeability rises. On impregnated paper, moisture also interferes with the cure state and the final strength.
Typical symptoms after moisture uptake
- Permeability reads high and pressure drop low, so filtration falls short;
- Stiffness drops and elements crush or show uneven pleat spacing;
- Pleating produces fuzz and dust, adding cleaning work;
- Impregnated paper feels soft, cures incompletely and loses strength in service.
Warehouse conditions
- Humidity: store in a dry, ventilated area away from water sources, steam lines and damp walls - particularly in the rainy season;
- Temperature: avoid high temperatures and sharp swings that cause condensation inside the roll;
- Light: keep out of direct sunlight to limit UV effects on fibre and resin;
- Segregation: do not store with chemicals, solvents or oils; the paper adsorbs odours and contamination.
Stacking and handling
- Stand rolls upright or lay them along the core axis on a pallet - long-term side pressure deforms the roll face;
- Limit stack height according to roll weight and packaging strength, heavy rolls low;
- Follow first-in-first-out so no roll sits for months;
- Re-wrap opened rolls; do not leave them uncovered overnight.
Tempering before use
In winter, or after a long journey, the paper can be well below workshop temperature. Opening the package and running it immediately causes condensation on the sheet - the same effect as deliberate moisture uptake. Let the sealed package stand in the workshop until the roll reaches room temperature, then open and use it.
In short: treat filter paper as paper, not as general stock. Warehouse humidity, stacking method and tempering cover a good share of the problems that otherwise only show up on the machine.