Rupert's Shot Maker

coot, I have no personal experience with the Prince Rupert shot making method, but I've long been interested in it, and have collected information on it. If done incorrectly, the shot frequently have curved 'tails' and that has resulted in the widely held but completely erroneous belief the it is 'swan shot'.

Robert Hooke, the famous 17th-century scientist, experimented with Rupert’s method extensively, probably in his role in the Royal Society, and wrote the report below to explain his results. It's kind of a recipe and historic record in one, very interesting to me, but quite long. BTW, Prince Rupert invented his method in 1663, I believe.

"To make small shot of different sizes; Communicated by his Highness P.R.

"Take Lead out of the Pig what quantity you please, melt it down, stir and clear it with an iron Ladle, gathering together the blackish parts that swim at top like scum, and when you see the colour of the clear Lead to be greenish, but no sooner, strew upon it Auripigmentum powdered according to the quantity of Lead, about as much as will lye upon a half Crown piece will serve for eighteen or twenty pound weight of some sorts of Lead; others will require more, or less. After the Auripigmentum is put in, stir the Lead well, and the Auripigmentum will flame: when the flame is over, take out some of the Lead in a Ladle having a lip or notch in the brim for convenient pouring out of the Lead, and being well warmed amongst the melted Lead, and with a stick make some single drops of Lead trickle out of the Ladle into water in a Glass, which if they fall to be round and without tails, there is Auripigmentum enough put in, and the temper of the heat is right, otherwise put in more. Then lay two bars of Iron (or some more proper Iron-tool made on purpose) upon a Pail of water, and place upon them a round Plate of Copper, of the size and figure of an ordinary large Pewter or Silver Trencher, the hollow whereof is to be about three inches over, the bottom lower then the brims about half an inch, pierced with thirty, forty, or more small holes; the smaller the holes are, the smaller the shot will be; and the brim is to be thicker then the bottom, to conserve the heat the better.
The bottom of the Trencher being some four inches distant from the water in the Pail, lay upon it some burning Coles, to keep the Lead melted upon it. Then with the hot Ladle take Lead off the Pot where it stands melted, and pour it softly upon the burning Coles over the bottom of the Trencher, and it will immediately run through the holes into the water in small round drops. Thus pour on new Lead still as fast as it runs through the Trencher till all be done; blowing now and then the Coles with hand-Bellows, when the Lead in the Trencher cools so as to stop from running.
While one pours on the Lead, another must, with another Ladle, thrusted four or five inches under water in the Pail, catch from time to time some of the shot, as it drops down, to see the size of it, and whether there be any faults in it. The greatest care is to keep the Lead upon the Trencher in the right degree of heat; if it be too cool, it will not run through the Trencher, though it stand melted upon it; and this is to be helped by blowing the Coals a little, or pouring on new Lead that is hotter: but the cooler the Lead, the larger the Shot; and the hotter, the smaller; when it is too hot, the drops will crack and fly; then you must stop pouring on new Lead, and let it cool; and so long as you observe the right temper of the heat, the Lead will constantly drop into very round Shot, without so much as one with a tail in many pounds.
When all is done, take your Shot out of the Pail of water, and put it in a Frying-pan over the fire to dry them, which must be done warily, still shaking them that they melt not; and when they are dry you may separate the small from the great, in Pearl Sives made of Copper or Lattin let into one another, into as many sizes at you please. But if you would have your Shot larger then the Trencher makes them, you may do it with a Stick, making them trickle out of the Ladle, as hath been said.
If the Trencher be but toucht a very little when the Lead stops from going through it, and be not too cool, it will drop again, but it better not to touch it at all. At the melting of the Lead take care that there be no kind of Oyl, Grease, or the like, upon the Pots, or Ladles, or Trencher.
The Chief cause of this Globular Figure of the Shot, seems to be the Auripigmentum; for, as soon as it is put in among the melted Lead, it loses its shining brightness, contracting instantly a grayish film or skin upon it, when you scum it to make it clean with the Ladle. So that when the Air comes at the falling drop of the melted Lead, that skin constricts them every where equally: but upon what account, and whether this be the true cause, is left to further disquisition."

The Project Gutenberg eBook, Micrographia, by Robert Hooke. 17th century.

BES: The material added was orpiment, a yellow arsenic sulfide material, As2S3. Orpiment takes its name from the Latin auripigmentum (aurum, "gold" + pigmentum, "pigment")

Spence

I certainly understand your concern. Addition of arsenic in some form appears to have been common, though, Moses Austin ran a lead mine in western Virginia in late 18th century, and also a shot tower on the New river nearby. August 1, 1791 he said, "...by experience I have found a much better mode to introduce arsnic and find the white much preferable to the yellow from its purity in strength."

Spence

I would imagine that the idea with the copy of Prince Rupert's shot maker coot is to pre heat it first, & then pour for as long as you can so that it does not cool down.

You will find my articles & primary documentation on shot & shot making here coot: woodsrunnersdiary.blogspot.com/2016/04/an-update-of-small-shot-for-smoothbores.html


woodsrunnersdiary.blogspot.com/2016/04/more-on-small-shot-for-smoothbores.html


woodsrunnersdiary.blogspot.com/2013/11/research-small-bar-lead-for-making-shot.html

Also, the lead won't stick to the unfluxed copper or the coals and the pour should be smooth.

Hi Coot,

In the book Colonial Frontier Guns by Hamilton, there are pictures of period rupert shot that were excavated at different sites.  The one thing they all have in common is the shot is not as round as shot from shot towers.  Each piece of Rupert Shot and no matter what the size,  has the characteristic "dimple" on the surface, that sort of looks a little bit like the dimple on the top of a heart shape.

Gus