To two quarts of linseed oil add half a pound of litharge, let it simmer over a slow fire for two or three hours; take it off and strain it, then add of finely powdered rosin a quarter of a pound, and white lead one pound, keep it in a gentle warmth, stirring it frequently till the rosin is dissolved and the whole well incorporated; then, if with this mixture you smear the bolt or strap previous to placing it in its place, and put a good coat on after on the parts exposed, your iron work will be effectually preserved from rusting from the effects of the atmosphere, or any wet that may get to your work.