Extract from the [Book Of Trades ] published 1780 .
The Gunmaker Section Barrel Forger
The last operation is that of colouring the barrel, previously to which it is polished with fine emery and oil,until it presents to the eye,throughout its whole length,a perfectly smooth and even surface.The practice of blueing,is now discontinued, and browning is adopted in its stead.To do this,the barrel is rubbed over with nitric,or sulphuric acid,diluted with water, and laid by until a coat of rust is formed upon it ,more or less according to the colour wanted;a little oil is then applied,and the surface being rubbed dry,it is polished by means of a hard-brush and beeswax.
Feltwad