Fire in my shop caused by old powder.

[Fishtail]

Yep!

When we were teenagers we accidentally set a rather large grass fire in the middle of a very dry spell in Texas by playing with firecrackers. It drew many fire trucks and took a few hours to get under control. Once the fire officials had time to question us, we assured them that we had noticed some broken glass in the ashes and offered our hypothesis that the sun's rays had passed through the glass and the magnifying effect had ignited the blaze.

Now, I'm quite sure the firemen knew we were lying through our teeth. But, they also seemed to appreciate that we were doing our part to help them explain the blaze in a manner which would minimize their paperwork back at the station and keep them from becoming entangled with the dreary workings of the county prosecutor. One hand washes the other, as it were.