Edward Porter Alexander makes reference to the Mexican powder causing excessive fouling. Fighting for the Confederacy-E.P.A.

Revoked is probably synonymous with reworking as mentioned by Lovell. The nitrates (salt peter) is the majority of the three chemicals being constituent of Black Gunpowder. The other two being charcoal and sulphur. Perhaps the powder wasn't good in the first place or suffered from degradement (Remember the barrel turners). The nitrates provide the Oxygen required for combustion of the material. Contaminated (by water or other combinate)nitrates would have prevented the powder from burning well, with reduced power (short rounds) and the excessive fouling mentioned by Alexander.

Still no word from DuPont.

Captured Confederate powder of Georgia manufacture was considered superior and was used by the Coastal Artillery until the mid-1890's.