Canning Lacquers

lacquers used to protect metal packaging from corrosion. They are based on prepared vegetable oils (oxidized linseed oil, dehydrated castor oil, and thickened tung oil) and some synthetic resins (butylphenol-formaldehyde and xylenol-formaldehyde resins and a mixture of epoxy and phenolformaldehyde resins). Turpentine, white spirit, butyl acetate, ethyl Cellosolve, and their mixtures are used as solvents.

The coatings formed upon drying of canning lacquers must be able to withstand the conditions under which canned foods are sterilized (about 120°C) and be resistant to the long-term action of protein and acid mediums, and they must not contain substances harmful to health or that change the appearance, smell, or color of the food product. These requirements are best met by coatings of lacquers based on synthetic resins. Protein-resistant canning enamels are produced by dispersion of certain pigments (such as aluminum powder or zinc oxide) in the canning lacquers.