Litter Pan

My boys have three glass Pyrex storage dishes filled with aspen shavings as litter pans. But, even when I replace the dirty shavings daily and wash them out weekly, some of the urine/bedding residue sticks to the pan and refuses to come off even with scrubbing with hot water and soap, unless I vigorously scrape it with a scraping tool. It works, but it takes a lot of effort and time. I don't really mind scraping the pans, but is it really necessary to scrape off the residue if I already...

Litter Pan