Plaster Casting Recipes:

BnF Ms Fr 640:

title id="p012r_a4 Plaster
<ab id="p012r_b4a Mountain[248] plaster is greyer, and that from the region of Albi is whiter. It has to be cooked[249] over a closed fire, such as a reverberatory furnace or a brazier. The more freshly cooked[250], the better it is to work with. It should be finely crushed on marble. After preparing your hollow mold of sulfur[251] or another [material] and oiling it and surrounding it with a circle, soak your plaster[252] in water, not too thick, and rub it well with your finger, and if it makes bubbles, throw on more powder of the said plaster and crush it [253][254]with your finger until ++ it makes no more bubbles. Then once more throw and sprinkle plaster powder on top and leave to set well, then scrape the powder off.

="p081r_a2">Earth for moulding
>Earth for moulding Sheath maker's earth or the one potters use to blanche the pots to make the lead flow better on it and to prevent the lead from soaking into them is very good to cast the hollow parts of what you want in relief. It releases better than plaster or sulphur which become hard once they have grasped on [to the mould] because earth sticks. It must be hit very hard so that it does not break. If the piece you want to mould is very large you can mould different parts separately. If you reheat it, it must be over a closed fire. You can find this earth at Le Fousseret[442], and in another place called Ox[443].
"p081r_a3">Plaster<
It must be very well cooked, you will come to learn when cooking it in an iron or metal casket. Mix it with an iron rod and if it sticks to the iron, it is not cooked enough, and if it doesn't then it is ready. The water with which you soak it has to be a little warm and the mould of the above mentioned earth or other, also should be a little hot. The plaster work does not last and the faces and delicate things break if you do not use glue

note id="p083r_c2">Plaster molds quite neatly but it swells. Bone does not have much body while iron dross does. Felt allows for an easy removal of the cast[465]
="p106r_b2b">For sand for molding flowers and leaves & other delicate things, mix in raw plaster, crushed brick and stone alum

"p106r_b2f">The snakes and the lizards you wish to mold should not be kept for a long

"p106r_b2g">Plaster of Paris is as hard as stone and very good. When you want to choose some for your sand, take the rawest and the hardest that is possible for you & that does not make any powder. Transparent [plaster] and that which makes powder in giving way is that which is not good for this work. A sign of that which is near perfect is that it is hard & makes shining grains that look almost like sugar. Finally, to mix it into the sand to cast gold, it has to be put in the fire twice, & reheated twice.

="p106v_b1d">Little turtles just out of the egg are really delightful to mold.
="p106v_c3e">If the plaster is mixed with some dust or is not the hard kind, [...] in the fire and make
="p106v_b3a">The hardest plaster, as was said, is the best, being taken thusly totally raw from stones of this kind. Crush it as finely as possible and pass it through the most fine sieve or sleeve that you can. Having been made fine in this way, put a good amount in a cauldron or frying pan over an open flame. & as it starts to heat up, stir it continuously. And heavy and lumpy though it is, it will become so light and so tractable that it will appear to you not to have any resistance to the said stirring, as though it were of water. Continue to keep stirring it continuously until it returns once again to being heavy and thick. And now this is the sign that it is cooked, but do not reheat it at all such that your stone alum brick be reheated & that clay circles form. Because this must be the last reheating, and when everything else is ready, because the less that the plaster remains reheated & the more suddenly it is put into the work, the better, because it takes rather better. It is not permitted to reheat it except when you want to mold. And to reheat it, put it, in fine, totally raw powder, in a cauldron on a clear flame & do not give it too much [heat] in one go nor too fierce. Stir continuously with a long stick, turning around the cauldron to avoid the vapor. And in the middle, in the form of a figure 8 at the beginning, you will find it heavy [and] clayey because it is full of moisture, [and] when it heats up, it will start to throw off [the moisture] in some bubbles on the edges of the cauldron. And finally it will become liquid & mealy and like bran and start boiling in the middle. Continue to stir continuously until you recognize that it has once again become heavy

="p106v_c3a">Plaster When you have it in stone form, choose the hardest pieces and those which do not easily break into small pieces with your nail, and clean it well of powder & filth rather than crushing them with it.
="p106v_c3b">Plaster alone does not sustain [...] but breaks up into lumps.
="p106v_b3c">Keep reheated plaster, as is said here, one or two months well compacted in a dry place, if it's not the rainy season but rather fresh out it is more excellent for exquisite work
="p106v_c3d">It must maintain its fire and turn red like lit charcoal.
"p107r_b2j">Try [to see] if distilled vinegar is good for eating away, it will dissolve the animal inside the hollow mold.
"p107r_c2">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.

="p111v_a4"> Lizards
="p111v_b4"> Hold the lizards by the two sides next to the ears with two fingers, make it open the mouth, then take the low mandible with the help of [...], then take the upper one. If the lizard bites your nail, it won't pierce it. But if the lizard grips your nail and bites your flesh and does not let go, the best solution is to cut its head quickly. Lizards are much more beautiful during spring when they shed their skin.
"p111v_c4"> Small lizards caught during the heat of summer, which are gray on the back and green under belly, are very good to cast with silver and gold or any metals, because the scales are harder than the lizards [...], and these scales are more visible
p111v_a5"> Making sand
="p111v_b5"> Reheated as it is above said, take four crucibles full of plaster, two crucibles full of brick, and one crucible full of feather alum. Do not sieve your feather alum it wouldn't pass through the sieve. Blend the mixture with your hands, at the end you should not distinguish anymore the white color from the red color. If your plaster is not strong enough, do not add so much feather alum, because feather alum soften molds. When you want to dampen your sand, be sure that your sand is not warm, as warm as it is straight after being reheated. Otherwise your molds would be too soft and would break.
"p111v_c5"> Reduce the quantity of plaster if it is not strong enough to withstand fire, and if it cracks [...] ground tiles and feather alum hold the mixture, you can add more feather alum and you'll have a better binder.
"p112r_a1">To wet the sand<
"p112r_b1">You should have: a large basin full of water to dip the molds into in order to open them, a tankard full of common water, a dish to wet the sand, a small wooden spoon to pick up the sand wetted in the dish
p112r_c1">To make handles for your large oil brushes, if you do not have large enough feather pipes, take two of them, melt them and join them together

"p112r_a3">Molding en noyau[738]. Mixing of sand
"p112r_b3">Once you have reheated your sand, that is the plaster, the stone alum and the brick, and once you have finely filtered them through a cloth sieve, # mix them the following way: take four measures of plaster, two measures of bricks, and one measure of stone alum. Mix them all together with the hands, so that one may not discern one [ingredient] from the other. Once your sand is ready, you need to kill the animal that you wish to mold in this way
"p112r_a4">Killing the animal to mold
"p112r_b4a">You must have been careful not to hurt it while capturing it. If you have a stock [of animals] and you wish to keep them for a long time, place it in a glass bottle with bran or in a large barrel half full of damp fresh earth. Give them frogs to eat, live rather than dead, because should you keep them without feeding them, they would wither and become emaciated, and their skin would become saggy and wrinkled. Therefore, the sooner after its capture you mold it, the better it will come out. And kill it in the following manner: place it in a clean bottle or vessel so that [the animal] does not carry any dust; fill [the bottle] with enough good vinegar and urine so as to cover [the animal]. Shake [the bottle] and torment [the animal] inside there until it is dead which should take an hour or half an hour. But if you are in a hurry
p112r_c4a">To know if [the animal] is quite dead, take it out of the vinegar and take it by the tail. If it moves its tail, do not mold it because it still has feelings[739], and when pricking [its members], it would remove itself and harm the mold.<
"p112r_b4b">to cast, force feed it [your animal] some good spirits or mix a bit of spirits with the vinegar. And soon it will be dead without any wounds that would deform it. As for large animals, for which it is necessary to have a lot of spirits, one uses vinegar and urine, but for small ones, spirits only are needed, and it will be done quicker
="p112r_b4c">When your animal is dead, take it out and clean it very carefully, [relieving it] of its old skin if it sheds, of its parasites, and then apply it.<
"p112r_c4c">in a glass, and submerge, continuously holding the head of the animal. Or if it is not very big, put the whole thing in.
p112r_c4d">Be advised that before it dies, you must open it eyes, by blocking its eyelids with a bit of wax or something else.
"p112v_a1">Affixing and arranging animals
="p112v_b1a">Having gotten in some fat earth called clay, that should be grey, because that is the best one, or another that will bind well and will be well prepared and beaten, so that it is malleable without being damaging your hands or the work, make a lazagne,[740] or a pancake shape, of this clay equally flattened with a rolling pin, which pastry-makers use so that it is slightly thicker than a poulc. [741] And on this pancake, affix your animal, making it as life-like as possible and the way in which it is naturally shaped. And firstly, with a good needle, pierce it from underneath, in the middle of the throat, up to the top bone of the head. Then take the needle out and in the hole, put the point of an iron wire, of such a length that it suffices to maintain the head of the animal as high as it must be, and if the skin gets in when you put in the wire, take it out with the edge of your small pincer[742], and arrange the skin as it was before. Pierce the other end of the wire in the sheet of clay. In this way the head will be held high, which will make it more graceful and proud. Arrange afterwards, the rest of the body, and the legs, and the curling as you think will look best. And so that it is secure and does not move when you put in the sand, secure the legs with little points of iron wire, having already made the first hole with a very sharp needle. Do the same on the body parts that you deem necessary, making sure that the points going through the animal are fixed in the clay sheet, and not so far in front that they jut out beyond the body of the animal by a<
"p112v_c1a">Take a needle of fine steel, and which will be the sharpest you can find, so that with it, when you make your first hole in order to place the wire threads, it will pass through without effort, and take care not to rudely insert the wire or take skin with it. Then put a thicker wire in the thick bits [of the animal] and the thinner wire in the thinner bits. But take this secret advice and do not plant your pointed wire in one go through the animal and onto the plaster, but having planted it, take it out of the clay earth but not out of the animal, which is afterwards fastened there. One does this because by fastening the point the first time, it pushes in the skin of the serpent and by taking the point out, it replaces the skin in its original state.
"p112v_c1b">When you reuse the points you have already used, make sure to clean them well of rust, so that they do not take away some skin.<
p112v_c1c">The main arrangement of your casting is to keep its head very high and have it looking sideways. For this effect, pierce the head on a solid plank or table, making the wire pass through the bottom of the throat up to the top of the head

"p118r_a1">Snails<
"p118r_b1">Those which are found in the ocean and similarly those in which certain small crayfish dwell are very beautiful for grottoes, if they have been rid of the first layer[762] of their shell with aqua fortis, because they really look to be made of mother of-pearl.<
p118r_a2">For removing flaws and whiskers[763][764] from things molded in a core mold<
p118r_b2">If your molds are made of good plaster which withstands fire, they will not crack, especially if they are squeezed well between two tables with presses or in a pot filled with ashes or sand, and, therefore, they will not develop flaws. If they they develop some [flaws[, you can remove them with a burin called "chaple," which has a tip like a small chisel.

"p125r_a1">Plaster<
="p125r_b1">When you mold something in order to cast with wax, first mold only plaster, you mold with plaster [that is] only reheated after [it] has been pulverized. Because, once [it] has been reheated on the stone slab, the outside[832] is burnt, and the inside remains nearly unburnt[833]. Transparent grey plaster is not strong, but the good one [plaster] becomes white once it has been soaked, and [it] sets well quickly. Nevertheless I have found the grey [plaster] to be quite firm and hard after it has set, but it takes longer [to work with it]. Know the nature of each. You will never mold very neatly if you do not soak until it is quite clear and liquid, your plaster or the core[834]'s sand. Soak it straight away after it has been reheated

"p125r_c1">However, if you mold with plaster that has been reheated once as said, coat the first mold well with oil. And when the second cast has set and you have prepared it, soak it in water for a long time. And if it does not strip[835], soak it in hot water, because cold water hardens it.

p125r_b2">And hot water softens it [plaster] more than cold water [which] does not penetrate it [plaster] as [it does] mixed plaster because it [plaster] is stronger and mixed plaster is spongier. Medals are cast from this powdered, reheated plaster, [and the medals] will be waterproof as though they were varnished. In Germany, people hang these medals on houses. See to it that the water is very hot, and if the water is boiling, it will not endanger [it]. All molds [made] of plaster only or molds [made of] mixed plaster are stripped from it.

p125v_a3">Plaster to cast with wax
"p125v_b3a"> When you want to cast in wax in a plaster mold, you must know this secret, that there is need that your mold be in hot water. The animal will never come out as clean as in metal, because wax grips. But to rough out an animal as close to natural as possible in order to fix it afterwards, you have to remove all the scales, because the wax will permeate them & will not be able to be stripped off. In molding the animal, take off the scales for wax, but on the contrary [when not molding with wax] rub them against their grain so that they raise up, because then these animals [sc. those not molded in wax and prepared in this way] will show better. Do not wait to strip off your wax until it is cooled down at all. But while it is a bit hot, after you have molded the first casting of the animal, uncover it halfway so that it be stripped in so doing. And having as much in one mold as in the other, make very many large castings holding on to the animal in order to fortify them [...] stripping, & afterwards you'll cut it.

p125v_b3b"> + Alabaster [...] which is plaster in any case, is very hard, but it shrinks quite a bit. It is good for making medals. But it must be very finely strained.<
p126v_a2">Plaster<
="p126v_b2">You can mould with plaster things as big as you like. If you want to mould a big work or something made of wood, it wouldn't be well stripped unless you soak wood with very hot wax. Because wood sucks and becomes impregnated with the mixture made from plaster. That is why you must soak wood with very hot wax, your work will be well stripped of the cast
="p126v_c2">Plaster is not good if it shrinks.

p127r_a1">Plaster mold for wax
p127r_b1">When your plaster mold is done and dried, be sure that your mold comes off cleanly because it sometimes happens that the animal, having been wounded or having lost weight or having withered, has wrinkles where plaster can get in the scales. Having not been rendered well, the animal will attack itself and break and will never be perfect. Be also advised to make your casts for wax very big. In this way, your casts will not be too thick. They are done when the mold of both sides is done and when the animal has been removed from the mold.
"p127v_b1a">This is churned[859] earth mixed in with dung or hairs which withstands fire, of which you must always have a large stock hanging around for dawbing the molds that you use to cast in silver and that need reheating. Those where you burn flowers or animals do not need dawbing, unless they have been left to stand once they have been reheated, and once they have been cleaned of any bones and ash that might have remained inside. And having removed the clamps, you open the two halves to see if they have any cracks. Because there is some plaster that does not harden as much in the fire as another one would. Others create crusts on the things that remain to be burned inside. And all of these are imperfections that you must avoid, either by giving the animal a bath of spirits before pouring your soaked sand, or by putting in more or less brick [sand] or alum, or by reheating the brick to higher temperature, or by instead of mixing in brick, mixing in broken bits of crucibles and similar things that resist fire well. Having therefore reheated your mold to burn what is inside, leave it to cool. And if it is neat and unbroken put the clamps on again, and dawb with the aforementioned earth, that is called of the founders, dust it with a bit of sifted ashes and leave it to strain. But beware not to dawb your if they are not cold. Those in which you cast silver, where nothing needs burning inside, only need, when the cast and the vents are made, to be dawbed and reheated once. Do not dawb the part of the mold in which you want to cast, but leave it uncovered like the openings of the vents

p139v_a1">Casting wax to mold an animal that one has not got Take some white wax which is much more appropriate for this kind of work than anything else, because it is much firmer and does not leave as much filth, as much as you need to cast the animal that you propose, and no more. And [take] a half quantity of ground coal and neatly sieved through a cloth or coal sleeve, using it to give some color to your wax, that would otherwise be transparent and you will not be able to see your lines as clearly. Put your wax on the coal fire to melt. And when it is well-melted and well-liquified, take a full eared-porringer of melted wax, [and] as much sulphur as the amount of a large pulverized walnut. Melt all of over a slow fire and when it is melted, do not leave it on the fire because it will become too hot. But take it off and keep stirring it with a little stick and when it has finished bubbling and is as liquified as water, cast it into the wax that you will have previously removed from the fire. And mix and stir both of the them so that they join together. After stir in little by little while continuously mixing, the charcoal that has been repeatedly ground, and in this way it will be very well incorporated. This is how you will know that your wax has gone beyond its ideal heating point, it will release no more smoke, it will start to have lines appearing on the side and not in the middle, and those lines will be close to each other. If you cast too hot, you will not be able to separate your wax from your mold and it would stick to the cast. When it is at the right state, stir it with a little stick so that the pulverized charcoal is well mixed in and has not fallen to the bottom of the mixture. And in this way, throw it in your mold bit by bit and not in one go, because wax is not runny.
And they need to be burned in the moule au noyau[916] rather than be opened like the ones that have something jutting out or an intertwining of legs and arms. And this wax, thanks to the sulphur, will melt with little heat and leave without leaving any filth. If by some misfortune the crushed charcoal remains in ashes, when you open the mold and blow on it, it will come clean.
p139v_c1b">To make wax serpents or other things to affix to candles, it is necessary to cast them with esbaucher[917] wax of all colors
"p139v_b1b"> not like other things. And for this one, you can cast two or three times until your mold is full. Now, concerning this mold of pulverized white plaster & reheated in the manner of the sand from the preceding recipes, you should have made it long ago because it is used many times. But, before using it, soak it for a good hour in cold water, & at a minimum, at least as long in hot water that at first is so hot that you can't hold your finger in it. And not that it absorbs no more, but that it appears very wet overall without water seeping into it. In removing it closed from the hot water, cast your wax in such a state of heat as has been described. And neither the first nor the second casting will readily come out well, hardly, until the mold is soaked. Let it cool down before opening it so that the cast thing not break. You will know that the casting is good when the wax coming back out of the mold is thin and even. Remember to make several castings along the whole length of the mold so that in this way the wax runs better.
"p139v_b1c"> Make the first casting twice as large as other molds. And if, in the first casting, your work fills with bubbles and in so doing does not come out neatly, it's all the same, because you have to face the fact that the three or four first do not readily come out well. Firstly, you will know whether there are a few barbs that keep it from stripping well. And you will remove them if, on their own, they do not remove themselves in the two or three first castings. And the more that you cast, the more you will do it neatly. And your mold will serve you more than one hundred times if it Is well governed. But it is good to soak it one night or one day before casting so that it be well soaked. The same must be done for fruits made from sugar. This wax is very soft & friendly & pliant, like copper. And if it is hard [this is] because of sulfur, which makes it melt more easily than than other [wax], so much that you can see evidence on a hot slate. And the sulfur that you put inside will be found the second time that you melt it, [as] cracks on the bottom. Having in this way passed through wax, it will not catch fire at all when put to a candle. And in this case, I believe that it will cast quite the medal [illegible]. One uses the same wax in place of varnish to
"p140r_c1c"> When your animal is cast, cut away the broth & superfluous things with a hot pen knife. And if you want, plait and wrap it around some stick or candle, put it in some hot water to soften and hold it in turning it around
protrusions of the castings so that they be even & that the wax has more silver so that it can run all in one go without turning through the windings of the snake.<

"p148v_a1">Molding turtles
="p148v_b1">Join the parts of your mold and fix very carefully clamps on all joints, which are on the top, the bottom and the sides of the mold; do not forget to notch the joints as you did with the other moulds. Once you have fixed all the clamps, remove the sides ones, not the others. Thus your mold, made of several pieces, will open as if it was only made of two parts. If you want to mould hollow, pierce a hole big enough to thread the end of your little finger in the middle of your mold's belly. Widen the outside of the hole, like clervois[951], in order to cast the core. You could avoid all these difficulties if you didn't mold hollow; you could then mold your turtle in two pieces, more quickly, and burn it inside of the mold like other animals. But a turtle is wheighty, and would be heavy if not molded hollow. This is why it is considered better to mold it that way. It takes 3 days to make the proper [hollow] mould. To mold hollow and fantastic [forms], you need very strong plaster which can withstand fire without bursting. But if you can't get this kind of plaster, add to it a little more stone alum, and also add crocum, which fortifies it [the plaster] and makes the flaws -- if there are any -- so fine that they can be easily removed. Do not forget to tighten your mould with a press in order to avoid flaws that happen when your mold is not tight enough, or when it bursts. To repair it, if the lines are not apparent enough retrace with a burin, then soften the lines with a ciselet[952]. You can remove the flaws with a chaple[953], a kind of burin. For the grumelures[954] and scales, they can be made with a gadet[955] or a small carving tool which isn't hammered, and hitting with a small file
p165r_a4">Plaster for molding
p165r_b4a">When it is long to set and dry, it means that it is too fat and moist, which is what makes it shrink away from the fire and crack. [This is] where burrs come from. The one that comes from lean earth is better. You must not store your moulds made of fat plaster for a long time, because they resemble fat earth, which when drying, cracks. The best is to reheat them[1034] soon after they have been made and cast. Moulds made of good plaster can be stored a long time
"p165r_c1">It is necessary to oil well, because it is more difficult to separate the two halves of these [kind of] moulds than when it is [made of] mixed [plaster]