A. In autumn and winter; because the capacity of the air for holding water being on the decrease, its vapour is deposited on every-thing with which it comes in contact.
Q. Why does greasing iron prevent its becoming rusty?
A. Because grease prevents the humidity of air from coming in contact with the surface of the iron.
Q. Why do not stoves rust so frequently as pokers and tongs?
A. Because stoves are generally covered with plumbago, or black lead.
Q. What is plumbago, or black lead?
A. A mixture of charcoal and iron filings.
A most excellent varnish to prevent rust is made of 1 pint of fat oil varnish, mixed with 5 pints of highly rectified spirits of turpentine, rubbed on the iron or steel with a piece of sponge. This varnish may be applied to bright stoves and even mathematical instruments, without injuring their delicate polish.
Q. Why does ornamental steel (of a purple or lilac colour) rust more readily than polished white steel?