• Silica gel is used to prevent condensation in an enclosed space.Chris Stein/Digital Vision/Getty Images
  
  Silica gel is a porous material used as a desiccant. It absorbs water vapor in the air and acts as a drying agent. Despite its name, silica gel is actually a solid and normally comes as granules. This desiccant is used to decrease the relative humidity in an enclosed space. This is needed where the possibility of mold or condensation can damage or degrade different products. Packets of silica gel help to preserve items.
  
  

Blue-Pink Indicating Silica Gel

• Blue silica gel is a type of self-indicating gel. When the silica is dry and does not contain any moisture, it appears deep blue in color. As the gel absorbs moisture, it will change from blue to pink. When the gel is pink, it will need to be regenerated in order to release the bound water and be usable again. The indicator for this type of silica gel is cobalt chloride, which is toxic. Creating and disposing of this type of silica gel is difficult because of the toxicity of the indicator.
  
  

Orange-Green Indicating Silica Gel

• Orange-green indicating silica gel works in the same way as the blue-pink variety. When the gel is dry, it is an orange color. As the gel absorbs water, it changes to a green color. Methyl violet is the indicator used in orange-green silica gel. This is organic and non-toxic, and is slowly beginning to replace blue-pink indicator.
  
  

Non-indicating Silica Gel

• White silica gel does not contain an indicator and will not change color as it absorbs water. This gel is frequently used in small desiccant bags. The bags will come with an indicator card that will show when the gel is full of water. These types of bags are frequently used for computers, cameras, musical instruments and preservation packaging.