Quick answer: This glossary defines the 31 terms you meet when buying paper or fiber desiccant, in plain English. The three that matter most: adsorption capacity (always quoted at a temperature and humidity), relative humidity (the condition your pack lives in) and format (card, sheet or bagged sachet). For ATMOSIScience fiber desiccant the headline figure is more than 10% of its own weight at 20% RH, more than 35% at 50% RH and more than 70% at 90% RH (25 °C).
Desiccant specs mix chemistry, packaging and quality language. If a datasheet or a supplier email uses a term you would rather not guess at, it is probably below. Terms are grouped so you can read a section at a time.
Performance terms
Adsorption
Water vapour held on the surface of a material's pores. Silica gel works this way; plant fiber does it through its micro-channels.
Absorption
Water taken into the body of a material. In everyday buying the two words are used interchangeably; specs should still state which test was run.
Adsorption capacity
How much water a desiccant takes up, usually as a percentage of its own weight, at a stated temperature and humidity. A capacity without a condition cannot be compared.
Relative humidity (RH)
How much water vapour air holds compared with the most it could hold at that temperature. Desiccant capacity is always quoted at an RH.
Equilibrium
The point where the desiccant and the air around it stop exchanging moisture. Capacity figures are often quoted at equilibrium.
Saturated capacity
The most water a desiccant can take up. ATMOSIScience bagged fiber desiccant can exceed 100% of its own weight when saturated.
Loss on drying (LOD)
Weight lost when a sample is dried, used to show how dry the material is on arrival. Fiber desiccant specifies below 10%.
Material terms
Plant-fiber substrate
The natural fiber sheet that carries the active ingredient and does the absorbing in a fiber desiccant.
Lignocellulose
The structural material of plant fiber. Its porous structure draws moisture into micro-channels by capillary action.
Calcium chloride
The active salt held in the fiber matrix of a fiber desiccant, which binds water chemically.
Capillary action
The way fine channels pull liquid or vapour along them. It is the physical half of how fiber desiccant takes up moisture.
Silica gel
Porous silicon dioxide beads or granules, usually sold in pouches. Common silica gel adsorbs about 30% of its own weight at 25 °C and 90% RH.
Paper desiccant
A flat desiccant that looks and handles like paper or card, used where a pouch will not fit.
Fiber desiccant
A desiccant whose absorbing layer is a plant-fiber sheet carrying calcium chloride. ATMOSIScience makes it as cards, sheets and bagged sachets.
Format terms
Desiccant card
A flat, relatively stiff desiccant used where a pouch does not fit or is not wanted. Not to be confused with a humidity indicator card, which reads humidity but absorbs almost nothing.
Fiber Desiccant Card
ATMOSIScience's card format at 0.7 mm for compact packaging or 1.0 mm for larger formats. At 1.0 mm it absorbs three times as much moisture as silica gel under the same test conditions (25 °C / 90% RH).
Fiber sheet
A thin plant-fiber desiccant sheet at 0.5 or 1.0 mm that can be cut square or round, used as a cap cushion, kit insert or garment tag.
Bagged desiccant
Fiber substrate of about 2.5 mm sealed in a pouch, from 1 to 1,000 g, for cartons, tubs, drums and larger enclosures.
Die-cut
Cut to a set outline, such as a disc that matches a jar or a shape that fits a cavity.
Surface printing
Printing a logo, product data or a do-not-eat line directly on the card.
Automated placement
Feeding desiccant from a stack or magazine and placing it into the pack by machine. Fiber Desiccant Cards are supplied ready for it.
Handling and packaging terms
Open-air exposure time
How long a desiccant can sit out of its sealed bag before packing. For fiber desiccant: up to 2 hours at 50% RH or below, up to 1 hour above that, and stop at 80% RH or above. If work pauses for more than 30 minutes, reseal the remaining desiccant in a sealed bag.
Bend test
The quick check for a Fiber Desiccant Card: a fresh card feels relatively stiff; one that has gone noticeably soft has absorbed moisture.
Unopened shelf life
How long the desiccant keeps in its original sealed packaging. Fiber Desiccant Card: 12 months from the manufacturing date.
MFG date
The manufacturing date, printed on the carton label next to the shipping label. Shelf life counts from it.
WVTR
Water vapour transmission rate: how fast moisture passes through a packaging material. Together with pack area and shelf life it sets how much water the desiccant must hold.
Headspace
The air space inside a sealed pack above the product, where a disc or card often sits.
Quality and buying terms
MSDS
Material safety data sheet. The fiber desiccant MSDS lists composition, physical properties and limits such as total bacteria of 1,000 cfu/cm² or less.
Grade D cleanroom
A controlled manufacturing environment class. Cleanroom report 20200266 (2020) recorded 10 areas at Grade D (static).
Recyclability assessment
A lab test of how a material behaves in paper recycling. SGS report CQMR260700043401 scored the bare plant-fiber sheet, as tested, 100 out of 100 as paper.
RFQ
Request for quotation. A good desiccant RFQ asks for capacity at several humidity points with the conditions stated.
Ready to put the terms to work? The paper desiccant spec checklist turns them into 15 RFQ lines, fiber desiccant vs silica gel packets compares the two side by side, and the fiber desiccant FAQ answers the common questions.
Missing a term?
Ask about any word on a desiccant datasheet. A real person will answer, and we can send samples if you are evaluating fiber desiccant.
Prefer email? info@atmosiscience.com
Figures from ATMOSIScience fiber desiccant product documentation and usage instructions, the Fiber Desiccant Card product sheet, the fiber desiccant MSDS, SGS recyclability assessment CQMR260700043401 (17 July 2026, bare plant-fiber sheet as tested) and cleanroom report 20200266 (2020).
