How to Determine if Color-Changing Silica Gel is Completely Ineffective
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The criteria of confirming the color-changing silica gel is totally ineffectual are: the colour is not recoverable, the physical structure has collapsed and it has lost moisture-absorbing function. It is no longer usable and has to be replaced.
1. Full Colour Deactivation: Indicator function loss
Blue Silica Gel – Does not turn deep blue, remains grayish-white, dark red or partly black after heating;
Orange Silica Gel: Dark green/green cannot revert to bright orange, colour is murky and dull;
Stagnation of colour changing reaction: No change of colour in humid atmosphere for a long time, or quick change of colour (loss of buffering ability).
Key Note: Cobalt chloride indicator has become degraded owing to long term thermal cycling or contamination and will no longer alter with humidity.
2. Destruction of physical structure: Collapsing of micropores
Indicators Normal State Total Failure
Particle Integrity Hard, intact Easily crushed into a small powder, with lots of fine debris
Looseness Free to rotate Clump, harden, or stay together badly
Touch dry & not sticky Residue wet, greasy or softened
If powdering or clumping happens, the silica skeleton is damaged and its adsorption capacity is lost forever.
3. Complete Loss of Functionality: No Ability to Absorb Moisture
(1) Moisture Test of Sealed
Operation: Put the regenerated and cooled silica gel in a sealed box for food storage that has a wet towel in it for 24 hours;
Judgement:
No colour change => Micropore block no reaction;
Rapid full colour shift → Destruction of structure, loss of gradual release capacity;
The normal colour change should be slow and even. (2) Verification of Capacity to Retain Dryness
Procedure: Place in a sealed box with cameras, medicines, etc. for a week;
Decision:
Discolouring in a short amount of time => Cannot keep a dry atmosphere, protection fails;
It is not recommended to continue to use it for moisture protection of high value items.
