OF STUCCO AND GESSO
FEW things are more disheartening to the pursuer of plastic art than finding that, when he has carried his own labour to a certain point, he has to entrust it to another in order to render it permanent and useful. If he models in clay and wishes it burnt into terra cotta, the shrinkage and risk in firing, and the danger in transport to the kiln, are a nightmare to him. If he wishes it cast in plaster, the distortion by waste-moulding, or the cost of piece-moulding, are serious grievances to him, considering that after all he has but a friable result; and though this latter objection is minimised by Mrs. Laxton Clark's ingenious process of indurating plaster, yet I am persuaded that most modellers would prefer to complete their work in some permanent form with their own hands.
Having this desirable end in view, I wish to draw their attention to some disused processes which once largely prevailed, by which the artist is enabled to finish, and render durable and vendible, his work, without having to part with it or pay for another's aid.
These old processes are modelling in Stucco-duro and Gesso.
Stucco-duro, although of very ancient practice, is now practically a lost art. The materials required are simply well-burnt and slacked lime, a little fine sand, and some finely-ground unburnt limestone or white marble dust. These are well tempered together with water and beaten up with sticks until a good workable paste results. In fact, the preparation of the materials is exactly the same as that described by Vitruvius, who recommends that the fragments of marble be sifted into three degrees of fineness, using the coarser for the rough bossage, the medium for the general modelling, and the finest for the surface finish, after which it can be polished with chalk and powdered lime if necessary. Indeed, to so fine a surface can this material be brought, and so highly can it be polished, that he mentions its use for mirrors.
The only caution that it is needful to give is to avoid working too quickly; for, as Sir Henry Wooton, King James's ambassador at Venice, who greatly advocated the use of stucco-duro, observed, the stucco worker "makes his figures by addition and the carver by subtraction," and to avoid too great risk of the work cracking in drying, these additions must be made slowly where the relief is great. If the relief is very great, or if a figure of large dimensions is essayed, it may be needful even to delay the drying of the stucco, and the addition of a little stiff paste will insure this, so that the work may be consecutively worked upon for many days.
From the remains of the stucco work of classic times left us, we can realise how perfectly workable this material was; and if you examine the plaster casts taken from some most delicate low-relief plaques in stucco exhumed some ten years ago near the Villa Farnesina at Rome, or the rougher and readier fragments of stucco-duro itself from some Italo-Greek tombs, both of which are to be seen in the South Kensington Museum, you will at once be convinced of the great applicability of the process.
With the decadence of classic art some portion of the process seems to have been lost, and the use of pounded travertine was substituted for white marble; but, as the bassi-relievi of the early Renaissance were mostly decorated with colour, this was not important. The ground colours seem generally to have been laid on whilst the stucco was wet, as in fresco, and the details heightened with tempera or encaustic colours, sometimes with accessories enriched in gilt "gesso" (of which hereafter). Many remains of these exist, and in the Nineteenth Winter Exhibition of the Royal Academy there were no less than twelve very interesting examples of it exhibited, and in the South Kensington Museum are some few moderately good illustrations of it.
It was not, however, until the sixteenth century that the old means of producing the highly-finished white stucchi were rediscovered, and this revival of the art as an architectonic accessory is due to the exhumation of the baths of Titus under Leo X. Raphael and Giovanni da Udine were then so struck with the beauty of the stucco work thus exposed to view that its re-use was at once determined upon, and the Loggia of the Vatican was the first result of many experiments, though the re-invented process seems to have been precisely that described by Vitruvius. Naturally, the art of modelling in stucco at once became popular: the patronage of it by the Pope, and the practice of it by the artists who worked for him, gave it the highest sanction, and hardly a building of any architectural importance was erected in Italy during the sixteenth century that did not bear evidence of the artistic craft of the stuccatori.
There has just (Autumn, 1889) arrived at the South Kensington Museum a model of the central hall of the Villa Madama in Rome, thus decorated by Giulio Romano and Giovanni da Udine, which exemplifies the adaptability of the process; and in this model Cav. Mariani has employed stucco-duro for its execution, showing to how high a pitch of finish this material is capable of being carried. Indeed, it was used by goldsmiths for the models for their craft, as being less liable to injury than wax, yet capable of receiving equally delicate treatment; and Benvenuto Cellini modelled the celebrated "button," with "that magnificent big diamond" in the middle, for the cope of Pope Clement, with all its intricate detail, in this material. How minute this work of some six inches diameter was may be inferred from Cellini's own description of it. Above the diamond, in the centre of the piece, was shown God the Father seated, in the act of giving the benediction; below were three children, who, with their arms upraised, were supporting the jewel. One of them, in the middle, was in full relief, the other two in half-relief. "All round I set a crowd of cherubs in divers attitudes. A mantle undulated to the wind around the figure of the Father, from the folds of which cherubs peeped out; and there were many other ornaments besides, which," adds he, and for once we may believe him, "made a very beautiful effect." At the same time, figures larger than life, indeed colossal figures, were executed in it, and in our own country the Italian artists brought over by our Henry VIII. worked in that style for his vanished palace of Nonsuch. Gradually, stucco-duro fell into disuse, and coarse pargetry and modelled plaster ceilings became in later years its sole and degenerate descendants.
Gesso is really a painter's art rather than a sculptor's, and consists in impasto painting with a mixture of plaster of Paris or whiting in glue (the composition with which the ground of his pictures is laid) after roughly modelling the higher forms with tow or some fibrous material incorporated with the gesso; but it is questionable if gesso is the best vehicle for any but the lowest relief. By it the most subtle and delicate variation of surface can be obtained, and the finest lines pencilled, analogous, in fact, to the fine pâte sur pâte work in porcelain. Its chief use in early times was in the accessories of painting, as the nimbi, attributes, and jewellery of the personage represented, and it was almost entirely used as a ground-work for gilding upon. Abundant illustration of this usage will be found in the pictures by the early Italian masters in the National Gallery. The retables of altars were largely decorated in this material, a notable example being that still existing in Westminster Abbey.
Many of the gorgeous accessories to the panoply of war in mediæval times, such as decorative shields and the lighter military accoutrements, were thus ornamented in low relief, and on the high-cruppered and high-peaked saddles it was abundantly displayed. In the sixteenth-century work of Germany it seems to have received an admixture of finely-pounded lithographic stone, or hone stone, by which it became of such hardness as to be taken for sculpture in these materials. Its chief use, however, was for the decoration of the caskets and ornamental objects which make up the refinement of domestic life, and the base representative of it which figures on our picture-frames claims a noble ancestry.
Its tenacity, when well prepared, is exceedingly great, and I have used it on glass, on polished marble, on porcelain, and such like non-absorbent surfaces, from which it can scarcely be separated without destruction of its base. Indeed, for miniature art, gesso possesses innumerable advantages not presented by any other medium, but it is hardly available for larger works.
Time and space will not permit my entering more fully into these two forms of plastic art; but seeing that we are annually receiving such large accessions to the numbers of our modellers, and as, of course, it is not possible for all these to achieve success in, or find a means of living by, the art of sculpture in marble, I have sought to indicate a home-art means by which, at very moderate cost, they can bring their labours in useful form before the world, and at the same time learn and live.