Now that I have determined the specs of silica gel, time to apply.

Let's dry a saturated 1kg spool of ABS. ABS water absorption is 0.2-0.4%, as I found from internet.

http://stephen-webster.co.uk/wp-content/uploads/2011/02/Thermoforming-materials-storage-and-drying-Athlone.pdf

-> 1kg spool can hold up to 4 g of water. So, I need no less than 27 g of cat litter to dry out one spool. Or 19 g of proper silica gel desiccant.