Velvril
"Velvril paint" was used to line larger common shells in the early 20th century to prevent the gunpowder filling from coming into contact with the iron or steel shell wall. This was both to avoid the saltpetre from causing corrosion in the presence of any moisture, and also provided a smooth surface that prevented friction between the gunpowder and shell wall, hence reducing the risk of spontaneous ignition when the shell was fired. It was made up of 24 parts zinc oxide, 3.5 yellow ochre, 0.5 red iron oxide, 15 nitrated castor oil, 7.5 nitro-cellulose of very low nitration, 60 acetone oil.
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