How to Determine if Color-Changing Silica Gel Needs Replacement

The main criteria for judging the replacement of color-changing silica gel are irreversible colour, damage to physical structure or loss of adsorption function. If there are apparent symptoms of ageing or pollution, even after thorough regeneration, it should be replaced.

1. Colour Status: If the colour shifting function is lost, replace it.

Normal operation Reverts fully from pink/dark green to deep blue/bright orange after heating.

Replacement Signals:

Colour is not recovered, traces of greyish white, dark red or localised blackening remaining;

Dull, not saturated;

Colour change uneven, some particles do not react,

The indicator (e.g. cobalt chloride) has been oxidised and deactivated and does not respond to humidity.

2. Physical Condition: Structural Damage Irreparably

Normal Replacement State Needs

Particle Integrity Hard, intact Crumbles easily to powder

Roll loose. Clump. Harden. Stick. Looseness.

Touch Dry and not TackyResidual dampness or excessively heavy

If there is a substantial amount of debris or clumps, it means that the microporous structure has collapsed and the adsorption ability is lost forever.

3. Functional Test: Real Moisture Resistance Test

(1) Humid Environment Test (Sealed)

How to use: Put the reactivated and cooled silica gel in a sealed food storage box with a wet cloth and leave it for 24 hours;

Ruling:

Slow, consistent colour change = normal function;

No colour shift or full quick colour change => Micropore blocked or failed, replace. (2) Test for Drying Capacity

Procedure: Put in a sealed box with precision items (such as cameras, medicines) for one week, then

Decision: (4)

No discolouration → Effective protection;

Short term discolouration => Insufficient adsorbing capacity, replace.

Practical Recommendation: If used for moisture protection of high value equipment, it should be replaced periodically to eliminate possible dangers.

4. USAGE HISTORY REFERENCE (TO FACILITATE DECISION MAKING)

Regeneration times >= 5 times: Performance generally below 70%, replacement advised;

Use for >1-2 years: Micropores may degrade through natural ageing, even if the appearance is normal;

Contact with oil, chemicals, or intense heat (>120℃): High risk of irreversible damage.

Special reminder: Blue silica gel with cobalt chloride is hazardous and releases harmful compounds more easily after ageing. It is not recommended to use it after its expiration date.