I asked Bart this question when my daughter died last year. He said that when screeners encounter difficulty with cremated remains, their usual practice is to put a quarter under the container and scan it again. If they can see the quarter, then it should pass OK. Apparently, while ashes are dense enough to look cloudy on the scanner, they are not dense enough to obscure metals.

Bart also told me that it would be wise to notify TSA in advance about what I would be carrying and when. I did not have any difficulties at the checkpoint.