Sforza Sculpture Hints
Some practical hints
OF A STATUE.
If you wish to make a figure in marble, first make one of clay, and when you have finished it, let it dry and place it in a case which should be large enough, after the figure is taken out of it, to receive also the marble, from which you intend to reveal the figure in imitation of the one in clay. After you have put the clay figure into this said case, have little rods which will exactly slip in to the holes in it, and thrust them so far in at each hole that each white rod may touch the figure in different parts of it. And colour the portion of the rod that remains outside black, and mark each rod and each hole with a countersign so that each may fit into its place. Then take the clay figure out of this case and put in your piece of marble, taking off so much of the marble that all your rods may be hidden in the holes as far as their marks; and to be the better able to do this, make the case so that it can be lifted up; but the bottom of it will always remain under the marble and in this way it can be lifted with tools with great ease.
Some have erred in teaching sculptors to measure the limbs of their figures with threads as if they thought that these limbs were equally round in every part where these threads were wound about them.
MEASUREMENT AND DIVISION OF A STATUE.
Divide the head into 12 degrees, and each degree divide into 12 points, and each point into 12 minutes, and the minutes into minims and the minims into semi minims.
Sculptured figures which appear in motion, will, in their standing position, actually look as if they were falling forward.
[Footnote: figure di rilievo. Leonardo applies this term exclusively to wholly detached figures, especially to those standing free. This note apparently refers to some particular case, though we have no knowledge of what that may have been. If we suppose it to refer to the first model of the equestrian statue of Francesco Sforza (see the introduction to the notes on Sculpture) this observation may be regarded as one of his arguments for abandoning the first scheme of the Sforza Monument, in which the horse was to be galloping (see page 2). It is also in favour of this theory that the note is written in a manuscript volume already completed in 1492. Leonardo's opinions as to the shortcomings of plastic works when compared with paintings are given under No. 655 and 656.]
Notes on the casting of the Sforza monument
Three braces which bind the mould
[If you want to make simple casts quickly, make them in a box of river sand wetted with vinegar.]
[When you shall have made the mould upon the horse you must make the thickness of the metal in clay.]
Observe in alloying how many hours are wanted for each hundredweight. [In casting each one keep the furnace and its fire well stopped up.] [Let the inside of all the moulds be wetted with linseed oil or oil of turpentine, and then take a handful of powdered borax and Greek pitch with aqua vitae, and pitch the mould over outside so that being under ground the damp may not [damage it?]
[To manage the large mould make a model of the small mould, make a small room in proportion.]
[Make the vents in the mould while it is on the horse.]
Hold the hoofs in the tongs, and cast them with fish glue. Weigh the parts of the mould and the quantity of metal it will take to fill them, and give so much to the furnace that it may afford to each part its amount of metal; and this you may know by weighing the clay of each part of the mould to which the quantity in the furnace must correspond. And this is done in order that the furnace for the legs when filled may not have to furnish metal from the legs to help out the head, which would be impossible. [Cast at the same casting as the horse the little door]
[Footnote: The importance of the notes included under this number is not diminished by the fact that they have been lightly crossed out with red chalk. Possibly they were the first scheme for some fuller observations which no longer exist; or perhaps they were crossed out when Leonardo found himself obliged to give up the idea of casting the equestrian statue. In the original the first two sketches are above l. 1, and the third below l. 9.]
THE MOULD FOR THE HORSE.
Make the horse on legs of iron, strong and well set on a good foundation; then grease it and cover it with a coating, leaving each coat to dry thoroughly layer by layer; and this will thicken it by the breadth of three fingers. Now fix and bind it with iron as may be necessary. Moreover take off the mould and then make the thickness. Then fill the mould by degrees and make it good throughout; encircle and bind it with its irons and bake it inside where it has to touch the bronze.
OF MAKING THE MOULD IN PIECES.
Draw upon the horse, when finished, all the pieces of the mould with which you wish to cover the horse, and in laying on the clay cut it in every piece, so that when the mould is finished you can take it off, and then recompose it in its former position with its joins, by the countersigns.
The square blocks a b will be between the cover and the core, that is in the hollow where the melted bronze is to be; and these square blocks of bronze will support the intervals between the mould and the cover at an equal distance, and for this reason these squares are of great importance.
The clay should be mixed with sand.
Take wax, to return [what is not used] and to pay for what is used.
Dry it in layers.
Make the outside mould of plaster, to save time in drying and the expense in wood; and with this plaster enclose the irons [props] both outside and inside to a thickness of two fingers; make terra cotta. And this mould can be made in one day; half a boat load of plaster will serve you.
Dam it up again with glue and clay, or white of egg, and bricks and rubbish.
[Footnote: See Pl. LXXV. The figure "40," close to the sketch in the middle of the page between lines 16 and 17 has been added by a collector's hand.
In the original, below line 21, a square piece of the page has been cut out about 9 centimetres by 7 and a blank piece has been gummed into the place.
Lines 22-24 are written on the margin. l. 27 and 28 are close to the second marginal sketch. l. 42 is a note written above the third marginal sketch and on the back of this sheet is the text given as No. 642. Compare also No. 802.]
All the heads of the large nails.
[Footnote: See Pl. LXXVI, No. i. This drawing has already been published in the "Saggio delle Opere di L. da Vinci." Milano 1872, Pl. XXIV, No. i. But, for various reasons I cannot regard the editor's suggestions as satisfactory. He says: "Veggonsi le armature di legname colle quali forse venne sostenuto il modello, quando per le nozze di Bianca Maria Sforza con Massimiliano imperatore, esso fu collocato sotto un arco trionfale davanti al Castello."
These bindings go inside.
Salt may be made from human excrements, burnt and calcined, made into lees and dried slowly at a fire, and all the excrements produce salt in a similar way and these salts when distilled, are very strong.
[Footnote: VASARI repeatedly states, in the fourth chapter of his Introduzione della Scultura, that in preparing to cast bronze statues horse-dung was frequently used by sculptors. If, notwithstanding this, it remains doubtful whether I am justified in having introduced here this text of but little interest, no such doubt can be attached to the sketch which accompanies it.]
METHOD OF FOUNDING AGAIN.
This may be done when the furnace is made [Footnote: this note is written below the sketches.] strong and bruised.
Models for the horse of the Sforza monument
Messer Galeazzo's big genet
Messer Galeazzo's Sicilian horse.
[Footnote: These notes are by the side of a drawing of a horse with figured measurements.]
Measurement of the Sicilian horse the leg from behind, seen in front, lifted and extended.
[Footnote: There is no sketch belonging to this passage. Galeazze here probably means Galeazze di San Severino, the famous captain who married Bianca the daughter of Ludovico il Moro.]
Occasional references to the Sforza monument
Again, the bronze horse may be taken in hand, which is to be to the immortal glory and eternal honour of the happy memory of the prince your father, and of the illustrious house of Sforza.
[Footnote: The letter from which this passage is here extracted will be found complete in section XXI. (see the explanation of it, on page 2).]
On the 23rd of April 1490 I began this book, and recommenced the horse.
There is to be seen, in the mountains of Parma and Piacenza, a multitude of shells and corals full of holes, still sticking to the rocks, and when I was at work on the great horse for Milan, a large sackful of them, which were found thereabout, was brought to me into my workshop, by certain peasants.
Believe me, Leonardo the Florentine, who has to do the equestrian bronze statue of the Duke Francesco that he does not need to care about it, because he has work for all his life time, and, being so great a work, I doubt whether he can ever finish it.
[Footnote: This passage is quoted from a letter to a committee at Piacenza for whom Leonardo seems to have undertaken to execute some work. The letter is given entire in section XXL; in it Leonardo remonstrates as to some unreasonable demands.]
Of the horse I will say nothing because I know the times. [Footnote: This passage occurs in a rough copy of a letter to Ludovico il Moro, without date (see below among the letters).]
During ten years the works on the marbles have been going on I will not wait for my payment beyond the time, when my works are finished. [Footnote: This possibly refers to the works for the pedestal of the equestrian statue concerning which we have no farther information in the MSS. See p. 6.]
The project of the Trivulzio monument.
THE MONUMENT TO MESSER GIOVANNI JACOMO DA TREVULZO.
 Cost of the making and materials for the horse .
[Footnote: In the original, lines 2-5, 12-14, 33-35, are written on the margin. This passage has been recently published by G. Govi in Vol. V, Ser. 3a, of Transunti, Reale Accademia dei Linea, sed. del 5 Giugno, 1881, with the following introductory note: "Desidero intanto che siano stampati questi pochi frammenti perche so che sono stati trascritti ultimamente, e verranno messi in luce tra poco fuori d'Italia. Li ripubblichi pure chi vuole, ma si sappia almeno che anche tra noi si conoscevano, e s'eran raccolti da anni per comporne, quando che fosse, una edizione ordinata degli scritti di Leonardo."
The learned editor has left out line 22 and has written 3 pie for 8 piedi in line 25. There are other deviations of less importance from the original.]
- A courser, as large as life, with the rider requires for the cost of the metal, duc. 500.
- And for cost of the iron work which is inside the model, and charcoal, and wood, and the pit to cast it in, and for binding the mould, and including the furnace where it is to be cast … duc. 200.
- To make the model in clay and then in wax……… duc. 432.
- To the labourers for polishing it when it is cast. ……. duc. 450.
- in all. . duc. 1582.
Cost of the marble of the monument
Cost of the marble according to the drawing.
- The piece of marble under the horse which is 4 braccia long, 2 braccia and 2 inches wide and 9 inches thick 58 hundredweight, at 4 Lire and 10 Soldi per hundredweight.. duc. 58.
- And for 13 braccia and 6 inches of cornice, 7 in. wide and 4 in. thick, 24 hundredweight……. duc. 24.
- And for the frieze and architrave, which is 4 br. and 6 in. long, 2 br. wide and 6 in. thick, 29 hundredweight., duc. 20.
- And for the capitals made of metal, which are 8, 5 inches in. square and 2 in. thick, at the price of 15 ducats each, will come to…… duc. 122.
- And for 8 columns of 2 br. 7 in., 4 1/2 in. thick, 20 hundredweight duc. 20.
- And for 8 bases which are 5 1/2 in. square and 2 in. high 5 hund'.. duc. 5.
- And for the slab of the tombstone 4 br. io in. long, 2 br. 4 1/2 in. wide 36 hundredweight……. duc. 36.
- And for 8 pedestal feet each 8 br. long and 6 1/2 in. wide and 6 1/2 in. thick, 20 hundredweight come to… duc. 20.
- And for the cornice below which is 4 br. and 10 in. long, and 2 br. and 5 in. wide, and 4 in. thick, 32 hund'.. duc. 32.
- And for the stone of which the figure of the deceased is to be made which is 3 br. and 8 in. long, and 1 br. and 6 in. wide, and 9 in. thick, 30 hund'.. duc. 30.
- And for the stone on which the figure lies which is 3 br. and 4 in. long and 1 br. and 2 in., wide and 4 1/2 in. thick duc. 16.
- And for the squares of marble placed between the pedestals which are 8 and are 9 br. long and 9 in. wide, and 3 in. thick, 8 hundredweight . . . duc. 8.
in all. . duc. 389.
Cost of the work in marble
- Round the base on which the horse stands there are 8 figures at 25 ducats each ………… duc. 200.
- And on the same base there are 8 festoons with some other ornaments, and of these there are 4 at the price of 15 ducats each, and 4 at the price of 8 ducats each ……. duc. 92.
- And for squaring the stones duc. 6.
- Again, for the large cornice which goes below the base on which the horse stands, which is 13 br. and 6 in., at 2 due. per br. …… duc. 27.
- And for 12 br. of frieze at 5 due. per br. ……….. duc. 60.
- And for 12 br. of architrave at 1 1/2 duc. per br. ……. duc. 18.
- And for 3 rosettes which will be the soffit of the monument, at 20 ducats each ………. duc. 60.
- And for 8 fluted columns at 8 ducats each ……… duc. 64.
- And for 8 bases at 1 ducat each, duc. 8.
- And for 8 pedestals, of which 4 are at 10 duc. each, which go above the angles; and 4 at 6 duc. each .. duc. 64.
- And for squaring and carving the moulding of the pedestals at 2 duc. each, and there are 8 …. duc. 16.
- And for 6 square blocks with figures and trophies, at 25 duc. each .. duc. 150.
- And for carving the moulding of the stone under the figure of the deceased ………. duc. 40.
- For the statue of the deceased, to do it well ………. duc. 100.
- For 6 harpies with candelabra, at 25 ducats each ……… duc. 150.
- For squaring the stone on which the statue lies, and carving the moulding ………… duc. 20.
- in all .. duc. 1075.
The sum total of every thing added together amount to …… duc. 3046.
MINT AT ROME.
It can also be made without a spring. But the screw above must always be joined to the part of the movable sheath: [Margin note: The mint of Rome.] [Footnote: See Pl. LXXVI. This passage is taken from a note book which can be proved to have been used in Rome.]
All coins which do not have the rim complete, are not to be accepted as good; and to secure the perfection of their rim it is requisite that, in the first place, all the coins should be a perfect circle; and to do this a coin must before all be made perfect in weight, and size, and thickness. Therefore have several plates of metal made of the same size and thickness, all drawn through the same gauge so as to come out in strips. And out of  these strips you will stamp the coins, quite round, as sieves are made for sorting chestnuts ; and these coins can then be stamped in the way indicated above; &c.
 The hollow of the die must be uniformly wider than the lower, but imperceptibly .
This cuts the coins perfectly round and of the exact thickness, and weight; and saves the man who cuts and weighs, and the man who makes the coins round. Hence it passes only through the hands of the gauger and of the stamper, and the coins are very superior. [Footnote: See Pl. LXXVI No. 2. The text of lines 31-35 stands parallel 1. 24-27.
Farther evidence of Leonardo's occupations and engagements at Rome under Pope Leo X. may be gathered from some rough copies of letters which will be found in this volume. Hitherto nothing has been known of his work in Rome beyond some doubtful, and perhaps mythical, statements in Vasari.]
POWDER FOR MEDALS.
The incombustible growth of soot on wicks reduced to powder, burnt tin and all the metals, alum, isinglass, smoke from a brass forge, each ingredient to be moistened, with aqua vitae or malmsey or strong malt vinegar, white wine or distilled extract of turpentine, or oil; but there should be little moisture, and cast in moulds. [Margin note: On the coining of medals (727. 728).]
[Footnote: The meaning of scagliuolo in this passage is doubtful.]
OF TAKING CASTS OF MEDALS.
A paste of emery mixed with aqua vitae, or iron filings with vinegar, or ashes of walnut leaves, or ashes of straw very finely powdered.
[Footnote: The meaning of scagliuolo in this passage is doubtful.]
The diameter is given in the lead enclosed; it is beaten with a hammer and several times extended; the lead is folded and kept wrapped up in parchment so that the powder may not be spilt; then melt the lead, and the powder will be on the top of the melted lead, which must then be rubbed between two plates of steel till it is thoroughly pulverised; then wash it with aqua fortis, and the blackness of the iron will be dissolved leaving the powder clean.
Emery in large grains may be broken by putting it on a cloth many times doubled, and hit it sideways with the hammer, when it will break up; then mix it little by little and it can be founded with ease; but if you hold it on the anvil you will never break it, when it is large.
Any one who grinds smalt should do it on plates of tempered steel with a cone shaped grinder; then put it in aqua fortis, which melts away the steel that may have been worked up and mixed with the smalt, and which makes it black; it then remains purified and clean; and if you grind it on porphyry the porphyry will work up and mix with the smalt and spoil it, and aqua fortis will never remove it because it cannot dissolve the porphyry.
If you want a fine blue colour dissolve the smalt made with tartar, and then remove the salt.
Vitrified brass makes a fine red.
Place stucco over the prominence of the….. which may be composed of Venus and Mercury, and lay it well over that prominence of the thickness of the side of a knife, made with the ruler and cover this with the bell of a still, and you will have again the moisture with which you applied the paste. The rest you may dry [Margin note: On stucco (729. 730).] well; afterwards fire it, and beat it or burnish it with a good burnisher, and make it thick towards the side.
[Footnote: In this passage a few words have been written in a sort of cipher—that is to say backwards; as in l. 3 erenev for Venere, l. 4 oirucremfor Mercurio, l. 12 il orreve co ecarob for il everro (?) co borace. The meaning of the word before "di giesso" in l. 1 is unknown; and the sense, in which sagoma is used here and in other passages is obscure.— Venere and Mercurio may mean 'marble' and 'lime', of which stucco is composed.12. The meaning of orreve is unknown.]
Powder … with borax and water to a paste, and make stucco of it, and then heat it so that it may dry, and then varnish it, with fire, so that it shines well.
STUCCO FOR MOULDING.
Take of butter 6 parts, of wax 2 parts, and as much fine flour as when put with these 2 things melted, will make them as firm as wax or modelling clay.
Take mastic, distilled turpentine and white lead.
On bronze casting generally
Tartar burnt and powdered with plaster and cast cause the plaster to hold together when it is mixed up again; and then it will dissolve in water.
TO CAST BRONZE IN PLASTER.
Take to every 2 cups of plaster 1 of ox-horns burnt, mix them together and make your cast with it.
When you want to take a cast in wax, burn the scum with a candle, and the cast will come out without bubbles.
2 ounces of plaster to a pound of metal;— walnut, which makes it like the curve.
[Footnote: The second part of this is quite obscure.]
[Dried earth 16 pounds, 100 pounds of metal wet clay 20,—of wet 100,-half,- which increases 4 Ibs. of water,—1 of wax, 1 Ib. of metal, a little less,-the scrapings of linen with earth, measure for measure.]
[Footnote: The translation is given literally, but the meaning is quite obscure.]
Such as the mould is, so will the cast be.
HOW CASTS OUGHT TO BE POLISHED.
Make a bunch of iron wire as thick as thread, and scrub them with [this and] water; hold a bowl underneath that it may not make a mud below.
HOW TO REMOVE THE ROUGH EDGES FROM BRONZE.
Make an iron rod, after the manner of a large chisel, and with this rub over those seams on the bronze which remain on the casts of the guns, and which are caused by the joins in the mould; but make the tool heavy enough, and let the strokes be long and broad.
TO FACILITATE MELTING.
First alloy part of the metal in the crucible, then put it in the furnace, and this being in a molten state will assist in beginning to melt the copper.
TO PREVENT THE COPPER COOLING IN THE FURNACE.
When the copper cools in the furnace, be ready, as soon as you perceive it, to cut it with a long stick while it is still in a paste; or if it is quite cold cut it as lead is cut with broad and large chisels.
IF YOU HAVE TO MAKE A LARGE CAST.
If you have to make a cast of a hundred thousand pounds do it with two furnaces and with 2000 pounds in each, or as much as 3000 pounds at most.
HOW TO PROCEED TO BREAK A LARGE MASS OF BRONZE.
If you want to break up a large mass of bronze, first suspend it, and then make round it a wall on the four sides, like a trough of bricks, and make a great fire therein. When it is quite red hot give it a blow with a heavy weight raised above it, and with great force.
TO COMBINE LEAD WITH OTHER METAL.
If you wish for economy in combining lead with the metal in order to lessen the amount of tin which is necessary in the metal, first alloy the lead with the tin and then add the molten copper.
How TO MELT [METAL] IN A FURNACE.
The furnace should be between four well founded pillars.
OF THE THICKNESS OF THE COATING.
The coating should not be more than two fingers thick, it should be laid on in four thicknesses over fine clay and then well fixed, and it should be fired only on the inside and then carefully covered with ashes and cow's dung.
OF THE THICKNESS OF THE GUN.
The gun being made to carry 600 Ibs. of ball and more, by this rule you will take the measure of the diameter of the ball and divide it into 6 parts and one of these parts will be its thickness at the muzzle; but at the breech it must always be half. And if the ball is to be 700 lbs., 1/7th of the diameter of the ball must be its thickness in front; and if the ball is to be 800, the eighth of its diameter in front; and if 900, 1/8th and 1/2 [3/16], and if 1000, 1/9th.
OF THE LENGTH OF THE BODY OF THE GUN.
If you want it to throw a ball of stone, make the length of the gun to be 6, or as much as 7 diameters of the ball; and if the ball is to be of iron make it as much as 12 balls, and if the ball is to be of lead, make it as much as 18 balls. I mean when the gun is to have the mouth fitted to receive 600 lbs. of stone ball, and more.
OF THE THICKNESS OF SMALL GUNS.
The thickness at the muzzle of small guns should be from a half to one third of the diameter of the ball, and the length from 30 to 36 balls.
OF LUTING THE FURNACE WITHIN.
The furnace must be luted before you put the metal in it, with earth from Valenza, and over that with ashes.
[Footnote 1. 2.: Terra di Valenza.—Valenza is north of
Alessandria on the Po.]
OF RESTORING THE METAL WHEN IT IS BECOMING COOL.
When you see that the bronze is congealing take some willow-wood cut in small chips and make up the fire with it.
THE CAUSE OF ITS CURDLING.
I say that the cause of this congealing often proceeds from too much fire, or from ill-dried wood.
TO KNOW THE CONDITION OF THE FIRE.
You may know when the fire is good and fit for your purpose by a clear flame, and if you see the tips of the flames dull and ending in much smoke do not trust it, and particularly when the flux metal is almost fluid.
OF ALLOYING THE METAL.
Metal for guns must invariably be made with 6 or even 8 per cent, that is 6 of tin to one hundred of copper, for the less you put in, the stronger will the gun be.
WHEN THE TIN SHOULD BE ADDED TO THE COPPER.
The tin should be put in with the copper when the copper is reduced to a fluid.
HOW TO HASTEN THE MELTING.
You can hasten the melting when 2/3ds of the copper is fluid; you can then, with a stick of chestnut-wood, repeatedly stir what of copper remains entire amidst what is melted.