A friend moved abroad and left me most of a pallet of pet supplies, including several bags of completely unknown age. This https://pacoandpepper.com/blog....s/news/does-cat-litt told me exactly what to check before using any of it and why some types hold up better in storage than others. The explanation of moisture getting in through the bag was the part I needed. Two bags were completely fine, one had gone solid at the bottom. Useful, specific and it saved me from a wasted afternoon of trial and error.