Lot numbers are imprinted on many products whose specific batch, group, or set may need to be tracked. Everything from lumber to medicine carries this identifying coding that tells manufacturers exactly which group is being referred to. When trying to pinpoint a defective batch of paint or contaminated cans of food, these numbers are invaluable. There is no guesswork involved; the numbers zero in on the batch that is suspect.

Other coding and marking on the container or can--barcodes, for instance--will reveal which plant produced or packaged the item. In the case of food products, this is key information, because every part of the process of preparing and packaging the food may need to be scrutinized. In assembly line plants, this involves time-consuming evaluations, but it is better than not knowing which of four or 15 plants the manufacturer should be concerned about.

Lot Numbers Provide Precise Information

Building materials also carry lot numbers, which are often printed on the back side of ceiling and floor tiles, gypsum board, shingles, and wall board. Any or all of these materials will probably be exposed to moisture and sunlight, so special lightfast inks must be used to print such identifying codes as lot numbers. With these permanent inks, bleeding and fading are minimized so any coding or text, such as the manufacturer's name, remains legible despite harsh conditions.

Entire cases of baby food, pet food, shampoos, canned goods, and cereals have these codes affixed. Not only are the individual units marked, but so is the corrugated cardboard that the cases are made of. Depending on whether the surface is porous, as in the cardboard, or non-porous, as in the cans, various kinds of inks are applied that are appropriate for the surface in order to produce a permanent code.