CHAPTER XIII. ON CARDINALS’ SEALS.
This sort of work is delightful. In my time in Rome, that was about 1525, there was a certain master from Perugia, called Lautizio, who practised nothing else but the making of seals for the bulls of cardinals. These seals are about the size of a ten-year-old child’s hand, and they are made in the shape of an almond. The cardinal’s title is engraved on them, and usually in the form of a rebus, or allegorically. Lautizio used to get at least 100 scudi for each seal he made. Now always sticking to my method of describing things from work I have done with my own hands, I’ll tell you of two that I made in this branch of my art.
The first was for the Cardinal of Mantua, brother of the Duke. On it was engraved the ascension of our Lady, with the Twelve Apostles, for so ran the Cardinal’s title. The other seal, much more richly figured, was for the Cardinal Ippolito of Ferrara, brother of Duke Hercules. On this one was engraved St. Ambrose on horseback, with a whip in his hand chastising the Arians. And as two stories had to be wrought upon it, for the Cardinal had a twofold title, it was divided down the middle and the legend of St. John the Baptist preaching in the desert was engraved on the other part, and both subjects were wrought with figures. For the Mantua seal I got 200 ducats, for the Ferrara one, 300.
The seals are made in the following manner. You take a smooth and polished black stone, and draw thereon the design you want to appear on the seal; and with black wax, a bit hardened, you fashion whatever relief you wish the seal ultimately to impress. When this is very delicately accomplished, you take a little volterrano gesso,[66] or any other gesso, provided it be very fine—boiled gesso it should be—& after having moistened your wax by painting it over very lightly with a fine paint brush and a little clean and pure olive oil, you put the gesso on your wax. You must mind not to get too much oil on your wax, for it would then hurt the gesso and prevent it from penetrating into the finer delicacies of the wax. Before pouring on your gesso in the liquid state, you must make a little wall or embankment of fresh clean clay, about two fingers high, all round your seal. As you pour your gesso on, you guide it about very carefully into all the interstices of the wax by means of a long-haired brush.[67] After the gesso is well set, remove it from the wax. This, of course, will be easily done, as there is no undercutting, for since the work is ultimately to serve the purpose of a seal, no projections are permissible. Then you clean out the matrix with a knife, removing any scum or spoiled surface that may have been made by the gesso on the inside, and polish it all up all round.
Now there are two ways of casting in silver, both of them are good and both of them will I describe to you. ’Tis true that one is a little easier than the other, but as I say, both are good and you may adopt whichever most wins your fancy. Do not, however, fail to try both, because it is good for you to learn them, & you will find them very helpful to you in many ways in other branches of the goldsmith’s art. The first method was the one employed by Lautanzio, and he, as I said, was the greatest master in this branch of work whom I ever knew. He used to take what is called earth for founding in boxes,[68] the same that all the bronze founders use, and from which they cast the harness of horses & mules, brass studs, and such-like trappings. And forasmuch as this clay is known all the world over, I shan’t bother about describing it, but only say that it is a kind of tufa earth. By the bye, as I write I am minded of a very rare kind of this tufa which is found in the bed of the Seine in Paris. While there I used to take what I wanted from hard by the Sainte Chapelle, which stands on an island in Paris in the middle of the Seine. It is very soft, and has the property, quite different from other clays used for moulding purposes, of not needing to be dried, but when you have made from it the shape you want, you can pour into it while it is still moist, your gold, silver, brass, or any other metal. This is a very rare thing, and I have never heard of it occurring anywhere else in the world.
Before considering the other kinds of clay that may be used for this sort of work, it will be best for me to tell you carefully how to make your gesso model for casting your seal from. After it is well cleaned with the knife in the way above described, powder it with a little fine charcoal-dust, or smoke it over with the soot from your lamp or taper; either will do, and I really needn’t describe this, because everybody knows how to do it. Then press the model into a caster’s sand-box of sufficient size to hold it conveniently.
This done, dry well that portion of the mould where the figures come (that is to say if you are using the Italian, not the Paris clay), then have ready a little dough[69] in the form of a cake similar in shape & thickness to what your silver or metal seal is finally to be, and put this over the figures formed by the gesso and which will appear in relief, having previously smoked over the mould with a little candle-smoke. This done, take the second box, fill it with the same moist earth and when dried set it upon the first. Mind in so doing that you do not disturb the part already dried where the figures are.[70] This second half you will easily mould. Then open the mould, and after taking out the dough-cake, make the mouths and the two vent holes, beginning at the bottom and going up as high as the mouth or ingress hole. When both parts are dry, smoke them over with a little candle-smoke and let them cool, have your silver well molten and then pour it in. Experience shows that it is better to pour the silver into cold than into hot matrices.
Now, for the second method, differing considerably from the first, but, as I have employed both, and the second not only for seals but for casting all sorts of other things too, I’ll describe it to you also. When you have from your original wax cast a gesso matrix in the manner above described, take a little of the same gesso, mix with it a little pith of horn[71] well dried, a further part of tripoli,[72] & finally another part of well-powdered pumice stone, and pound these four parts well up together. Then add as much water to them as shall give them the consistency of a paste—neither too thick nor too fluid. Then with a fine brush paint the surface of your seal all round over the wax projections and into the interstices, with a little olive oil. Waiting till it is well dried in the way we Florentines call verdemezzo, that is to say neither too dry nor too moist,[73] make a little wall of clay about two fingers high all round it, and pour the above mixture into the work and paint it well in and around the whole of your subject. Pile the mixture up at least two fingers high and make about four fingers more of it at the upper end on account of the almond form which is the shape your seal will be, for you need there greater size for the pouring-in mouth of your silver or whatever metal you may be using. When the gesso is thoroughly dried, which will not be till some four hours or so, separate the one piece of gesso from the other, taking very great care that none of your design is injured. As you may well imagine, it was much easier to separate the matrix from the wax in the first method than from the composition in the second, because in the former it had a firmer consistency. If some of the arms and heads don’t appear to you to come out quite a success, and remain stuck in the matrix, you can remedy that in either of the following ways. You can either pick out the bits remaining in the mould with a small paint brush, & re-apply them with a little powdered tripoli, and since your design is in relief you will easily see the impressions made by it in the mould. Or, for the other way, you can clean out the mould entirely, paint it round again and fill it up with the composition in the same way as before; often if the first turn has not come out well, the second does.
But pay the greatest possible attention to what I am going to tell you now. Make a waxen form, almond-shaped, and of the exact size your seal is to be, hollow it out, and lay it over the surface of your gesso relief. Then make your little ramparts of earth about this wax, taking heed to make due provision for the channel of the casting, which should be of ample length; & here I ought to tell you that the longer your channel is the better chance your work has of turning out well. There are no end of little details still to be observed, but if I were to tell you all of them I might as well begin teaching you your A B C. So I assume that my readers are people who have mastered the first principles of the Art. I would remind you, too, that both the ingress mouth & the vents have to be made of wax & applied to the wax core. These vents are fixed below, & turn up around the seal towards the ingress mouth; they must not, however, come in contact with the latter, because they have to do their own work of drawing out the air.[74]
This done, bind up your seal with well-tempered iron or copper wire, and let it bide in the sun, or some place where it can get warm & well dried. Then put it in your little furnace of tiles and iron hoops and melt out the wax with such heat as may be needful. Of course your wax must have been free from all impurities or it would never melt out properly. And when you have melted it out you make the fire stronger till your mould is regularly burnt, & the more it is baked the better your work will be. Then let it cool, and because the silver adapts[75] itself more readily to the cold than to the hot mould—cold, mark you, but not moist—when it is well molten pour it in. But ere you do this, in order that it may not burn,[76] strew a little borax over it and upon that a handful of well ground tartar,[77] and you will find this help your work wonderfully. Then dip the mould in water in order better to separate it from the silver, and so break it open. This done clean the silver off at the points where the channel & the vent holes come, and give it a subtle finish with the file. After this, in order to give the seal its final touches, you place it on the pitch, and, with your first gesso matrix before you, work the silver with your punches, gravers and chisels, touching up and completing your subject now here, now there, figures, swags, arms, bodies, legs, all alike, accentuating[78] them in the matrix with your steel tools. To see better how you are getting on, you may occasionally press in a little black wax, or whatever colour pleases you better, to gauge the projections. Now note this: my custom was to cut out the heads, hands and feet of my figures on small steel punches, and thinking the work came clearer and got a better result, I struck these punches with dexterous strokes upon the seal with a hammer into their different places. Also you should make in a similar manner an alphabet of steel punches, likewise many other conceits according as taste prompts. When I was in Rome, or elsewhere, working in this line, I ofttimes amused myself by making new alphabets, each for its occasion, for they wear out soon, and I got much credit by my inventiveness. Your letters should be well formed, & shaped as a broadly cut pen might shape them; the strokes going up or down with the action of the hand, the letters being neither too fat and stumpy, nor too long and thin, for both these are unpleasing to behold, the moderately slim ones are the nicest to look at.