Quote Originally Posted by kb3lms View Post
The blix had a gray sludge that had settled in the bottom of the container and won't wash out.
Silver rich sludge that should not be disposed of in landfill or down the drain - Send it off for reprocessing or see if your local council has a toxic waste disposal facility.

As for cleaning, I've used a thick toilet bleach to clean trays before now and have also tried Cilit Bang. Sodium Hydroxide is also good for removing (some) deposits.