Making and Knowing
A minimal edition of BnF Ms Fr 640 in English Translation

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[Information on casting]

The sand mixture is made of two thirds of ground plaster, reheated as it is said before, and of one part of reddened tiles which are finely ground afterwards. Use also stone alum, half of the quantity of the tiles. Use two full pots of plaster, one pot of tile and half a pot of stone alum. Do not use too much stone alum because that binds the sand, and allow sand to withstand fire without cracking or breaking. Without it [stone alum] sand would not withstand fire, you can use it for all kind of metal, but for gold add a bigger quantity of stone alum, add also crocum ferri, because they [these filings] attract gold.

All the sands you will cast, must withstand fire very well, it must withstand high temperature without spoiling anything.

It is difficult to grind stone alum, and it cannot be sieved, you must grind it on a marble slab. The white [stone alum] powder the apothecaries sell is good, it is easy to crush it into a mortar, use the pestle slowly, that way you will make it [the stone alum] very fine.

Crocum ferri must be heated into a glassworker’s furnace during four days.

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Molds for fine things, like wormwood or something similar, can only be used once, dip the molds into water before breaking them. Things twice reheated are dissolve easily into water. If you don’t do that your work will be hard to be stripped of the mold without being spoiled.

Good stone alum is white and as shiny as white silk, this stone alum is made of long pieces, as long as a finger, and is very fragile and woolly and fluffy. Stone alum made of stone is harder and not so good. The best quality can be found in France near Ronan. For our sand, stone alum must be crushed into a mortar, and must be ground on the marble again. Don’t even think about sieving it because this matter is fat and woolly, it wouldn’t pass through any sieve because of the very fine and soft filaments. These filaments give the sand a much greater binding effect than natural wool or even the filler the foundry owner uses for big works, because natural wool and filler burn and stone feather alum resists fire.

When you cast surround the sand of your mold with very beaten greasy earth. Make a circle around your mold with this earth.

Archanum omnibus fere reconditum est in re fusoria, v{idelicet} res exprimenda formis, sive herba sit sive animal ut lucerta, inmergatur primum in vini spiritum aprime rectificatum, deinde pulvere composito aspergatur sive illinatur (si pulvis in formam pultis redactus sit, ut assolet)

When you want to mold something hollow, the core must be made of the same matter, if the snake or the animal is curved or folded you must do your core in several pieces.

Try [to see] if distilled vinegar is good for eating away, it will dissolve the animal inside the hollow mold.

at left top margin of folio 107v

If you know that your plaster cannot endure fire without breaking, do not take the recipe of the mixture literally, sometimes you can add less stone alum than above. Because stone alum soften molds. Once reheated do not grind the stone alum again, leave it ground as the apothecaries did. It will not prevent the cast from being neat, and will give more binder to your cast. When the mold holds the color of the brick and is reddened then it will be harder.

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To hold the cores, some [people] use wire made of the same metal as that to be cast because it boils down and is made similarly, but when it is melted or pliant the core varies. Other [people] find it serves them better to use sharpened iron wire about the borders because it holds more firmly, and having fine points it does not rise up any more than the point of a needle and one can apply gold or silver on this rather than putting it in works [where] one makes a hole in the work with a small chisel.

Spirits prevent the sand from bubbling and do not make little holes on the borders of the mold if the thing to be molded is very damp, the holes and farts and bubbling does not make it in the place of the mold which is thick but at the borders which are more delicate.

One casts ordinary silver of the sort goldsmiths coarsely work, which is made with mediocre alloys. And when one casts with solder, it runs even better.

Spalt is a whitish stone which can be found in Germany, mainly in Augsburg from which can be made the most excellent sand that can be found for [casting] lead, tin, copper, silver and gold. And the more it is used, the better it is. It is clean for casting flat things in a frame. For rounded things, it is not as attractive [because it] does not hold in the fire as the aforementioned [things] composed of plaster.

The snippings of [a] large [piece of] greasy leather are good to cast in melted copper and brass because they clean it and take away from it all its filth.