The core criterion for determining whether color-changing silica gel has been activated after cooling is whether the color has completely returned to its initial dry color. For example, blue silica gel should be a uniform deep blue, and orange silica gel should return to a bright orange, and it should be properly sealed and stored after cooling.
1. Color Restoration: Direct Evidence of Activation
Blue silica gel (containing cobalt chloride): After complete regeneration and cooling, it should be a uniform deep blue, without any reddish, grayish, or mottled hues.
Orange silica gel (cobalt-free, environmentally friendly): It should return to a bright orange, and the dark green color that appeared when it failed should completely disappear.
Key Note: Color is a direct reflection of the indicator's state. Color restoration = normal indicator function = effective activation.
2. Auxiliary Judgment Methods
|
Method |
Operating Instructions |
Judgment Basis |
|
Tactile Inspection |
Gently squeeze the particles. |
Loose, no lumps → Intact structure; Hardened or powdery → Possibly damaged by overheating. |
|
Sealing Test |
Place in a transparent sealed bag and let stand for 1 hour. |
No fogging, no discoloration → No moisture absorption, activity remains good. |
|
Environmental Exposure Test |
Place in a humid, sealed container for 24 hours. |
Slowly changes from blue to pink → Normal moisture absorption function, activated. |
If the color does not recover after heating (e.g., grayish-white, dark red), it indicates regeneration failure and incomplete activation.
3. Precautions
Cooling process must be completed in a dry environment: It is recommended to cool naturally in an oven with the power off to avoid airflow introducing moisture.
Avoid delayed sealing: Seal within 5 minutes after cooling to prevent the newly restored dryness capacity from being negated by ambient humidity.
Record the number of regenerations: Even if the color recovers after more than 5 regenerations, the adsorption capacity may decrease; effectiveness needs to be evaluated in conjunction with the usage scenario.
In practical applications, "complete color restoration + stability after cooling + timely sealing" are the triple guarantees for confirming activation.
