Gross cleaning of a Thermos

Something I didn't think would get so dirty was my thermos. We have two... mostly from when both me and En were taking coffee to work since we didn't have good coffee at work.After cleaning one, I was shocked.So, I documented the second one.Before:After:The shocking thing was how it got clean. I dumped some dishwasher detergent into it and let it sit a bit. When I dumped it there was flakes of crud coming out.Here's the dumping of second one:Tell me that isn't a bit crazy?