How sailing warships kept sparks out of powder magazines

Why did powder magazines use copper and why did powder handlers avoid ordinary shoes?

Copper helped exclude damp and sparks, while barefoot workers or special footwear avoided hobnails and other sources of ignition around loose powder.

Copper was not armor; it helped keep powder dry and spark-free. Powder handlers avoided ordinary nailed footwear, sometimes using slippers but often working barefoot. Powder monkeys carrying charges between the magazine and guns could be as young as seven or eight. The precautions reflect black powder's sensitivity and the catastrophic stakes of a magazine fire.