How to Determine if Color-Changing Silica Gel is Fully Regenerated

The main requirement for complete regeneration of the color-changing silica gel is the return of the colour to the original dry colour. For example, blue silica gel should be blue all the way through and orange silica gel should be orange.

 

1. Restoration of colour: the most immediate basis of judgement

Blue Silica Gel (with cobalt chloride): It is pink or red when it is useless, and should be of a consistent deep blue when completely regenerated.

Orange Silica Gel (cobalt free, environmentally friendly): When it fails, it is light green to dark green; following regeneration, it should turn back to vivid orange.

Key Note: If there are still localised red, greyish or uneven colouring patches, this signals incomplete regeneration and heating should continue.

 

2. Auxiliary Method of Judging

Materials and Methods

Instruction for Use

Criteria for Judging

Observation on cooling

Allow to cool naturally to room temperature in a switched off oven.

Prevent the interference of colour judgement by heat absorption of moisture.

Feel and touch

Take out the particles and lightly squeeze.

Loose, no lumps → Good regeneration Hardened or powdery → Structural damage

Environmental testing

Store the regenerated silica gel with some moisture in a sealed container for 24 hours.

If the colour shift is slow (blue → pink), the moisture absorption function is normal.

If the colour does not return after heating, it may be that the temperature is too high (>120℃), causing cobalt chloride to be oxidised and deactivated.

 

3. Cautions

Don't open the oven midway: Opening the oven frequently may produce temperature changes, which will damage the regeneration effect.

Single layer heating: To ensure even heating. Thickness no more than 5cm.

Note the number of regenerations: even if the colour recovers after more than 5-10 regenerations, the adsorption capacity may have dropped dramatically.