Arguments rumbled on and there were endless delays. Early versions of the sticky bomb were prone to leaks as well as breakage in transport. There were understandable concerns over the explosive charge, pure nitroglycerin is notoriously susceptible to the slightest knock but the mixture developed by ICI proved to be very safe even if it should get into the hinges of the storage boxes.[26] By December 1940, fewer than 66,000 had been produced and the rate of production was disappointing at five to ten thousand per week.