It's worse than that!
Here's a picture of the area about 10' behind where I was shooting.
[/url]
The rag (one of several) and the other can of powder were all in a canvas bag of toys directly behind and in the flight path of the fuses blown clear of the mortar! A helpfull observer noticed and put out the burning shop rag very quickly!
Let's see - is it a good idea to have a wooden box for powder, matches and fuse? Perhaps one with a lid that can't be propped open?
Maybe a little less distractions (like taking pictures)