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A desiccant TDS (technical data sheet) tells you whether a product will do your job — but only if you read the right numbers. The four that matter most are the adsorption capacity at a stated relative humidity, the grade or pore type, the form and unit weight, and the purity figures (pH, moisture content and, where relevant, trace metals). A capacity quoted without the humidity it was measured at means very little; a grade given as "silica gel" with no pore type or grain size means less. This guide lists what a usable data sheet should show, and what to do when a figure is missing.
| Field on the TDS | Why it decides the purchase | What a usable figure looks like |
|---|---|---|
| Adsorption capacity | Sets how much desiccant you need for a given moisture load | Quoted as % of own weight, at stated relative humidity and temperature |
| Grade / pore type | Decides whether the gel works at your humidity | Type A (narrow), Type B (medium) or Type C (coarse) pore, stated |
| Form and unit weight | Decides how it fits the pack or the bed, and the count you order | Bead size in mm, or sachet weight (our industrial range runs 0.5 g to 1000 g) |
| pH | Contact safety and compatibility with the packed goods | A range measured in a dilute aqueous suspension |
| Moisture content | Shows the gel arrives dry, i.e. not partly spent | A "loss on drying" figure, low, on the as-supplied product |
| Regeneration temperature | Decides whether you can dry and reuse it | A maximum, by type — e.g. no higher than 200 °C for narrow pore |
Capacity is the headline number, and the one most easily misread. Silica gel holds more water at high humidity and less at low humidity, so a single figure is meaningless without the relative humidity (RH) it refers to. Two sheets can both say "absorbs up to 30% of its weight" while describing completely different performance: one measured at 80% RH, the other at 20% RH. Always read capacity as a value at a stated RH.
"Silica gel" on its own is not a specification. The pore type decides behaviour: narrow pore adsorbs best at low humidity, coarse pore at high humidity, with Type B between them. A TDS that gives a capacity without a pore type is telling you the average of several different products. Our silica gel type codes guide sets out how the codes map to behaviour, and our Type A narrow pore silica gel page shows the fields we publish.
For a sealed pack, the number that matters is the sachet weight and material; for a bed, it is the bead size. Our industrial desiccant sachets, for example, run from 0.5 g up to 1000 g and are offered in composite paper, non-woven, OPP film and other sachet materials, so the TDS should state the weight, the sachet material and the packed form. A weight with no material, or a material with no weight, is half a specification.
Purity is where the data sheet earns its place for food, pharmaceutical and export applications. Look for pH, moisture content, and any trace-metal or heavy-metal figures your market requires. Two compliance regimes are now routinely quoted on desiccant data sheets for European buyers:
Where a coloured indicating gel is involved, check whether the indicator is cobalt-based — the point of our cobalt-free indicating silica gel article.
If you intend to dry and reuse the gel, the TDS should give a maximum regeneration temperature by type. As a working guide, narrow pore silica gel is regenerated without exceeding about 200 °C, coarse pore gel tolerates much more, and colour-indicating gel must stay low (around 120 °C) or the indicator is destroyed. Our silica gel regeneration guide gives the temperatures and methods.
Do not guess the missing number — ask for it, and ask for the certificate of analysis for the actual delivery, not only a generic data sheet. A supplier who can answer on capacity-at-RH, pore type, moisture content and material, and back a compliance claim with a document, is the one to buy from. How to bind those figures into the order itself is set out in how to write a desiccant specification for a purchase contract.
The figures above are typical values from supplier data sheets; where a standard or regulation is named, the number is given:
Written by the VEN Desiccant export team from the data sheets and declarations our suppliers issue and from the compliance regimes our buyers ask about. Drafting was AI-assisted; the figures and the standard numbers were checked and edited by our team before publication. We publish it to help buyers read a TDS critically and ask for the right evidence, not to rank for a keyword. Always treat the certificate of analysis for your actual delivery as the controlling document.
Last checked: 11 October 2026.
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