Desiccant suppliers will always tell you that the most important factor to consider when selecting a desiccant is the absorption capacity. It seems perfectly logical that the more moisture a desiccant can absorb the better it should be. However, what they are not telling you is that you also need to consider the application (where is the desiccant being used) and unique characteristics of the desiccant when making your decision.
Let’s illustrate this point using the example of silica gel desiccants and calcium chloride desiccants. Calcium chloride can absorb up to 300% of its own weight in moisture, compared to 30-40% for silica gel. Surely the ability to absorb 10X more moisture makes calcium chloride a far superior desiccant? This is not necessarily the case. It’s like saying a sports car is always better than a 4X4 because it is faster, but what if you’re driving on a muddy trail…
Application – Inside a Package Versus Inside a Shipping Container
Where the desiccant is being used is fundamentally important. Calcium chloride needs high levels of sustained moisture to perform, which you do not find inside packages. Inside packages the humidity is less extreme and is not sustained, and under these conditions calcium chloride absorbs poorly. It is not able to absorb much moisture and the rate of absorption is very slow. Silica gel desiccants/Clay desiccants thrive in such conditions and will outperform calcium chloride, reducing the humidity inside the package faster and to significantly lower levels.
The opposite is true inside shipping containers where the humidity is extreme and sustained. Calcium chloride performs optimally in these conditions and has the capacity to remove the necessary amount of moisture to prevent container rain.
Silica gel desiccants will be overwhelmed under such extreme conditions and they do not have the capacity to remove sufficient moisture. Silica gel desiccants/Clay desiccants is not a suitable ingredient for container desiccants.
