What if the color-changing silica gel doesn't recover its original color?

The colour of the silica gel not returning to the original colour means failure of regeneration. It can be because of extreme temperature, ageing of the structure or pollution. In this instance it is vital to evaluate if it can continue to be utilised or replace it directly.

1. Most common causes of failure of colour recovery

High regeneration temperature (>120 °C)

Cobalt chloride indicator is deactivated and oxidised, unable to change colour again. They are grayish-white or dark red.

Deep Moisture Absorption Not Treated in Time

Moisture penetrates deep in the microporous structure and total desorption is difficult. Consequently, regeneration is imperfect.

Multiple regeneration and ageing of structure

The micropores of the silica gel collapse after 5-10 regenerations and hence reduce the adsorption capability.

Contamination with organic matter or oil

Clogs pores not removable by heating. Affects colour and performance recovery.

If the colour after heating is grayish-white, dark red or brown then in most cases the failure can be considered irreversible.

 

2. Countermeasures: Verify if the device is functional.

Context

Suggested activity

Partial colour recovery (e.g. pink with blue)

Can be utilised temporarily in non-critical situations (e.g. toolbox moisture protection) but is not advised for precise equipment.

Nothing at all (red/green = red/green)

Has lost its signalling function and the greater part of its adsorption capacity. Must be renewed.

Fragmentation/pulverization of particles

Damaged microporous structure; irreversible. Replacement needed.

For usage in food, pharmaceuticals and electronic gadgets.

It is suggested that even if partially recovered, replacement be done for safety reasons.

Practical suggestion: Mark the packing "Regeneration Failed" to avoid misuse.

 

3. Key points to prevent regeneration failure

Temperature control : When using the oven , set to 100 ~ 120 ℃ , in order not to overheat .

Regeneration at the appropriate time: Process where the colour change is 1/3 to prevent total saturation.

Clean operation: Prior to regeneration, do not allow oil or liquids to contact it.

Record number of regenerations Reinforce monitoring after ≥5 regenerations. Disposal may be advised after ≥10 regenerations.

Industry practice: Silicone that does not return to its original colour is discarded in the laboratory and is no longer utilised for moisture protection.