These Sachets are made from tyvek and have thousands tiny perforations. The silica gel they contain is colour changing to show when they need to be dried out. They are orange when dry and will turn to green as moisture is absorbed from their environment.
When dry and gel is orange these sachets weigh 500g or under as the colour changes it’s weight increases. This helps when to come to drying them out as you will see that weight will go down as the water is removed. These sachets will cover an area of about 3 square meters. They work well when placed in with your printer’s filament to keep it dry and protect from damp. The colour change is clearly seen.
Drying the silica can be done in various ways, low heat in an oven or in the airing cupboard. The method that I use is the microwave. Beware that the silica gel gets very hot using this method So use oven/heat proof gloves when using this method.
Place the absorbent paper upon a microwaveable plate so that water will be collected and set the timer for 5 mins, keep a eye upon it and maybe if needed take it out before the end and shake so it’s evenly heated, allow to cool, then weigh it if not equal or less than 500 grams place back and give it a few more minutes then repeat the above until it’s 500 grams. Allow it to fully cool before placing it back in your filament storage box.
More information about Silica Gel here