Desiccants absorb water out of the air before it has a chance to contaminate whatever they are packed in. Eventually, though, the desiccant will reach a point where it can no longer absorb any more water. Most retail desiccant packs are only intended for one-time use. But the water can be removed from homemade desiccants by simply using a household oven.
Silica gel is the easiest material for a homemade desiccant. It is readily available at most craft stores because it is used to dry flowers. Silica gel can absorb about 40 percent of its weight in water. Once it absorbs that much water, it is no longer capable of absorbing moisture from the air. But it is a relatively simple regeneration process to remove water from the desiccant. Regenerating silica gel returns the ability of it to absorb water from the air.
Homemade Desiccant Containers
Vitamin bottles and similar containers make good homemade desiccant containers. Fill one of these bottles or a similar container with silica gel. Then tape two coffee filters over the opening to cover it. The filters allow moisture in the air to enter the bottle but will prevent the crystals from falling out if the desiccant pack is knocked over. It is a good idea to put a label on the side of the bottle with the weight that the homemade desiccant will reach when it needs to be regenerated.
The silica gel absorbs water from the air, which increases the weight of the gel. There are two weight measurements that should be taken when making a homemade desiccant. The first is the weight of the container when it is empty. The second is the weight of the container filled with silica gel. Subtracting the empty weight from the full weight will give the weight of the silica gel. Multiplying this weight by 1.35 will give the weight of the gel when it is almost full of water. Add this weight to the empty container weight. This final weight should be marked on the bottle to indicate what weight it will need to reach before it should be regenerated.
When the gel is near the point it can no longer absorb water, it needs to be regenerated. The regeneration process is quite simple. Remove the silica gel from the container and place it on a baking sheet. This baking sheet should be used only for regenerating homemade desiccants because not all silica gel is food-safe. Heat an oven to 300° F. Place the baking sheet in the oven for three hours. Once removed, allow it to cool before placing it back in the containers. After regeneration, the desiccant packs should function like new.