From what I read it seemed to be the ingredients used in the serpentine powder would tend to seperate after a while causing a slower burning . So the mixture if allowed to setup very long would need to be remixed. But in doing the remixing process it would release a ,sometime explosive gas into the air. To insure a sale I am sure this information wasn't pasted along by the Mexican Golverment !! But knowing how the Mexican Goverment was so corrupt it may have been some really old gunpowder stored up in a warehouse somewhere.