Silica Gel Blue

Cobalt Chloride Visual Indicator

Silica Gel Blue is amorphous silicon dioxide formed by precipitation from sodium silicate, washed, dried, and impregnated with anhydrous cobalt chloride at low loading. The cobalt chloride is dark blue in the anhydrous state and turns pink as it hydrates, giving the bed a clear visual signal of remaining capacity without instrumentation.

SorbiTech manufactures the SorbiTech indicating grade as 2 to 5 mm and 3 to 8 mm beads, with a surface area of 650 to 800 m²/g and a water capacity of 30 percent or more at 80 percent relative humidity.

Where the Visual Signal Matters

The classical application is the transformer breather. As the transformer cools, atmospheric air is drawn through the breather, and a saturated bed allows moisture into the oil and accelerates insulation degradation. The Silica Gel Blue colour change from blue to pink is visible from the inspection platform, so the operator schedules replacement before the bed loses protective capacity.

The same logic applies to instrument enclosures, archival storage, photographic equipment shipment, and high value packaged goods where remote monitoring is not justified.

Regeneration and REACH Note

A spent Silica Gel Blue bed is regenerated thermally at 120 to 180 °C in air or under low vacuum, which drives off the captured water and restores the cobalt chloride to the anhydrous state. The blue colour returns at the end of regeneration and the bed is back in service.

Cobalt chloride is listed under the EU REACH regulation as a Substance of Very High Concern. SorbiTech supplies Silica Gel Blue where the application explicitly calls for the cobalt chloride indicator, and we recommend the cobalt free Silica Gel Orange grade as the modern alternative for new installations in regulated jurisdictions.

Forms and Supply

Manufactured to ISO 9001:2015 as 2 to 5 mm or 3 to 8 mm beads, supplied loose in 25 kg drums, in 1 kg sealed bags, or pre packaged in stainless steel transformer breather cartridges to SorbiTech specification. SorbiTech supplies the blue grade in pre packaged transformer breather cartridges and bulk; see the cobalt free orange alternative, the parent silica gel family, and applications under gas treatment and drying.