Hello everyone,

 

I am wondering about Humidity Card. It is used for many purpose different Industries. Simply, it is a card that absorbes the humidty and changes colour. Slica gel is used for as an absorbing material. But the challange is how do they provide the relativity. I saw the original product. It has levels from 20 to 60 and when it absorbs the humidity first 20 than 40 and finally 60 turns from blue to pink. How can this be done? I attached a picture in order to be understand better. You can see levels. If anyone has an idea please let me know.

 

Thanks.

The fundamental change is due to cobalt ions picking up water and changing from blue to pink. The presence of other ions and salts affects the RH at which that change occurs.

 

http://en.wikipedia.org/wiki/Cobalt(II)_chloride

Hello John,

 

Could you be more specific? Whch ions or salts make this happen?

 

Regards.