Note by Conduitt on tempering puncheons

Puncheon

It is made of steel which is brought from Germany & costs about 7d a pound, it is bound about with iron round & at the bottom to prevent its cracking by the force of the press –

Before the Egraver works upon it it is nealed – that is, it is put into a charcoal fire where the head is to be downwards

vidi– When the head is made it is put into a round iron vore Which has in it dust of leather burnt made of old shoes the head is put downwards & where, that is some of the said dust finely sifted is put & that & the other dust together round it so high as to prevent any air coming to the head, for if any air came it would scale it, sometimes wood soot is used but that does not performe the work smooth so well as dust of leather — Then it is put into a charcoal fire, where it is kept about half an hour if the furnace has not been, heated before if it has less time will do they judge when it is proper to take it out by seeing whether it is red hot in all its partes — They neal the water that is it with a red hot iron bar & then take the puncheon out of the fire & put it as quick as they can into the water for if it stays too long in the air it will scale, & stir it about in it as long as it hisses & then leave it 4 or five minutes afterwards in the water to cool, for if you take it out too soon it <8v> will crack & fly, then clear the puncheon with sand & water & then try by a file & chissole wether it be hard if it turns the chissell it is hard enough — When it happens to be too much hardened they heat 3 iron rings & put them when red hot round the puncheon but when it is too soft they haue no remedy —

Die —

<9v>

Course of a puncheon.