How much grams of silica gel should I put for my 4.6L air tight dry box? I have a silica gel inside of a plastic sachet but I cut the plastic and put it in a small open container to absorb moisture more effectively. Any suggestions how much should I put?
A 5 liter container will have about .1g of water at 100% humidity at room temperature.
Each time you open the container most of the air in it will mix with room air. If your environment is 80% humid then the silica gel will adsorb about .08g of the water. Silica gel saturates at about 40% of its weight but to keep things dry you should limit it to 10% or less.
So, for your box, 10g of silica gel will keep things quite dry for about 15 openings or so. More if your room averages 50% humidity, less if it's really humid. You can re-use silica gel by heating it at 250F for a few hours which drives most of the water out.