Some packaging materials are questionable as regards their halal status. In many
cases, stearates of animal or vegetable origin might be used in production of plastic
bags and containers. Waxes and coatings applied to plastic, paper, and Styrofoam
cups and plates might be from animal fat following the very hot annealing stage,
which is hot enough to nullify any animal products found prior to that step. Metal
cans and drums can be contaminated with animal fats. Formation, rolling, and
cutting of steel sheets to make containers requires the use of oils to aid in their
manufacturing. Such oils can also be animal derived (Cannon, 1990). Steel drums,
which are often reused, can be used to carry foods containing pork or pork fat,
which, despite rigorous cleaning practices, might remain in small amounts to
contaminate halal products otherwise thought pure.