How to Determine if Color-Changing Silica Gel is Aging

The basic criteria to assess if the colour changing silica gel is ageing are: colour cannot be recovered, particles are broken or pulverised and adsorption capacity has considerably reduced which does not improve even after adequate regeneration.

 

1. Three Visual Signs of Ageing

Signs of Ageing Indicators of Judgement Normal State

Colour Restoration Ability Fully restored to blue or orange following heat treatment Partially restored or unmodified (e.g. greyish-white, dark red, brown)

Physical State Particles are intact, firm texture Cracks, shattering, pulverisation, or softening and clumping occur

Moisture Absorption Properties Changes colour slowly when in a humid climate (blue to pink) A very fast colour shift or no colour change suggests collapse of the microporous structure.

Key Note: When the colour can not be restored entirely after heating, it can be fundamentally concluded that the indicator function is faulty. Even if some adsorption capacity is still remaining, it does not recommend to use in crucial moisture-proof scenario.

 

2. Additional Means of Judgement

Method Operating Instructions Signs of ageing

Regeneration Test Heating By conventional process (baking at 100 to 120℃ for 1 to 2 hours) Colour unchanged or only partially restored

Usage Duration and Number of Uses Check if it has been regenerated 5 times or used for more than 1 year. Once the limit is passed the performance degradation accelerates.

Environmental Testing Exposure Place the cooled silica gel in a sealed container with humidity for 24 hours. No colour change means no response, quick complete colour change means adsorption out of control, both are abnormal.

"In laboratory, adsorption capacity decreases more than 30% after 5 regenerations" is typically employed as the ageing and elimination benchmark.

 

3. Causes of ageing and prevention tips

Major Causes:

If the regeneration temperature is too high (>120℃), the cobalt chloride will be oxidised;

Failure to address without delay repeated deep moisture absorptions;

Oil and organic debris plugging micropores;

Long time exposed to high temperature and humidity environment.

Warnings:

The regeneration temperature should be controlled between 100-120℃; Regenerate when colour change is 1/3 of the way to total saturation; Keep clean and free from contamination before regeneration; Log the number of regenerations and increase monitoring after a cumulative total of ≥5 regenerations.

Practical tips: old silicone should be marked "Invalid" and stored separately to avoid being used inadvertently in precision equipment such as cameras and hearing aids. Keep away from dampness.