For years I have thought the silica gel bag inside a brief case, camera bag, hand bag, shoes and electronics protected these products against damage by damp and condensation during shipment from China and the surrounding areas.
As a company which manufactures and sells silica gel bags, we wanted to investigate this practise of using desiccant bags to protect goods in shipping by sea.
There are contrasting opinions about the real benefit deriving from the use of these bags due to their small size and, more important, from the fact that the goods are not sealed or kept in an enclosed environment. And ultimately this would lead to rapid saturation of the silica gel bag.
Experts who work for companies in the moisture protection field would approach the problem in a different way. They would probably want to know the material of the item to be protected, its volume, the typical ambient conditions (temperature, relative humidity, etc.), the storage duration, etc... And they will all come out saying that a small silica gel bag (1-3 grams) would not be able to protect anything because of the limited amount of desiccant and the absence of a sealed container.
We have now had some opportunity to test how a 3 grams silica gel bag inside a briefcase protects against humidity in different ambient conditions.
A safe environment for leather goods will maintain ambient temperature and relative humidity within a certain range. Mould would start to appear when the relative humidity exceeds 60%. However, an excessive desiccation would dry out the goods deteriorating the material. For this reason, the relative humidity should never decrease below approximately 45%RH.
The results of test showed that in extreme humid conditions, typical of a maritime environment, the sachet saturates in a week on average. This certainly doesn’t cover the shipping time.
In room ambient conditions (22°C and 35%) the sachet has a quick initial adsorption and once it exceeds half of its adsorption capacity, the adsorption process gets slower. The point when it slows down is reached in approximately 15 days, which it is still very short.
We initially thought that when the temperature varies, that little silica gel bag that was saturated before, reactivates a decent percentage of its adsorption capacity to be able to adsorb again during the next cycle.
This theory couldn’t be proved by the test.