The Decoration of Leather Part 8

"Now that the art is less in vogue, we think it a suitable time to describe it to the public, thus following the intention of the Academy of allowing nothing to be lost that may now or hereafter be useful to the cause of art. We may at any time be desirous of returning to these older fas.h.i.+ons, no longer being able to vary them, and this may be among those destined to return to favour. At any rate, it will be agreed that some of its processes merit description, and might find their application in other arts and help in bringing them to perfection."

[Ill.u.s.tration: 20. EMBOSSED CALF BINDING. _BOOK OF COMMON PRAYER._ EXECUTED BY ROSALIE VIGERS FROM A DESIGN BY FREDERICK VIGERS. MODERN ENGLISH.]

The same author describes minutely and very clearly the various processes in use at the time for gilding or silvering leather. Instead of silver-gilt, which is necessarily very costly, he recommends silver leaf burnished and covered with a varnish, for which he gives the following recipe, found by him, as he modestly acknowledges, among the papers of Mons. de Reaumur:--

"Take four and a half pounds of colophony, the same quant.i.ty of ordinary resin, two and a half pounds of sandarach and two of aloes; mix these four drugs together, after having broken up those which are in large pieces, and put them in an earthen pot on a good charcoal fire. It is better for the fire to be of charcoal, because it makes but little flame, which would be dangerous if it should enter the vessel, as the ingredients are very inflammable. To guard against this accident and others of which we will speak later on, the vessel must be chosen large enough not to be more than half-filled by the drugs already mentioned and the others yet to be added, as will presently be explained. It is well also for it to widen out at the top, or to have a rim that will project the flame outwards. These are small precautions which it is always better to take; some, however, neglect them, and make their varnish on a wood fire, and then double attention must be given to prevent the drugs igniting.

"Melt all these drugs in the pot and stir them with a spatula so that they mix together and do not stick to the bottom. When they are well melted, pour in seven pints of linseed oil and mix it with the drugs, using the spatula. Cook the whole, stirring it from time to time to prevent as much as possible a kind of sediment which forms and does not mix with the oil from sticking to the bottom of the vessel. When the varnish is cooked, pa.s.s it through a cloth or strainer.

"This quant.i.ty of varnish should, according to workmen, remain seven to eight hours on the fire to cook, but this cannot be regarded as an invariable rule. It will not take so long to cook on a large fire. A better test used by workmen in manufacturing varnish is to take a few drops of the liquid with the spatula and lay it over silver leaf on some leather; or else they take some of the varnish in a silver spoon and, by trying it with the finger tip as if it were syrup, find out if it is cooked enough.

If it ropes in cooling, or if the finger has a tendency to stick when it is gently withdrawn, it is a sign that it is sufficiently cooked, that is to say that it has arrived at the consistency of a thickish syrup. The varnish is then brown in colour, and curiously enough when laid over silver it becomes transparent and gives the effect of brilliant gold."

While on the subject of gold groundwork made with gold or silver leaf or tin-foil covered with varnish to imitate the colour of gold, it is curious to note how far back in the history of art its origin can be traced; after the Greeks, the Byzantines made use of and, it may also be said, abused it. This want of moderation in the use of gold is to be met with long afterwards, for it is mentioned in his book on painting by L. Benedetto Alberti who died in Rome in 1472.[18]

[18] _Sunt qui auro immodice utantur, quam aurum putent historiae affere majestatem._ L. B. Alberti, _De Pictura_, Book 2, page 25, _ad finem Vitruv. Elzevir. f._

Van Orley, Raphael's pupil, when painting his "Last Judgment" at Antwerp, had his panel gilt in order to obtain "a beautiful transparency."[19]

[19] Decamps. _Vie des peintres flamands._ Paris, 1753, 4 vols. Vol. 1, page 39.

We have quoted above the formula for golden varnish given by Fougeroux de Boudaroy which he ascribes to Reaumur. It may be found interesting to compare with it that given by the Monk Theophilus in his _Diversarum Artium Schedula_:--

"Put some linseed oil in a small new pot; add some gum arabic called _fornis_ pounded very fine; this gum is like very light incense, but is more brilliant when broken up. Place it on a charcoal fire and cook it carefully without allowing it to boil, until it is reduced by one third. Be very careful of flames, for they are very dangerous, and the preparation is difficult to extinguish if it once catches fire. Any painting coated with this varnish becomes brilliant, beautiful and perfectly lasting....

"Another method. Arrange three or four stones which will stand the fire without breaking, or bricks may be used instead. On these place a new pot, pour into it some _fornis_ mentioned above, called by the Romans "glossa," otherwise gum arabic. Over the opening of the pot, put a smaller one having a little hole at the bottom; fill in with clay so that no s.p.a.ce remains between them. Carefully light a fire underneath the apparatus until the gum liquefies. You will also have a thin tool with a handle which will serve to stir the gum and to find out the exact moment when it becomes perfectly liquid. Have a third pot on charcoal by you in which there is hot linseed oil; when the gum is quite liquid, so that a thread of it hangs from the tool when it is withdrawn, pour in the hot oil, stir with the tool, and, when in this condition, cook all together without letting it boil, take out the tool from time to time and spread a little of the mixture on wood or stone to try its density. With regard to the proportion, be careful that there are two thirds of oil to one of gum. When it is cooked according to your judgment, take it off the fire and, covering it with care, let it cool.

"_Of the Method of Colouring Tinfoil to give it the Appearance of being Gilt, so that it may be used when Gold cannot be had._

"Place the pieces (of tinfoil) side by side on the board, fasten them one by one to the wood with wax, so that they cannot get displaced, spread over them with the hand a coating of the varnish described above, and let them dry in the sun. After that take some sticks of rotten wood cut in April, slit in half and smoke dried. Peel off the outer bark and the second, which is the colour of saffron; sc.r.a.pe it into a clean vessel, adding to it a fifth part of saffron, macerate it well in old wine or ale; after letting it stand during the night, make it lukewarm the next morning. When in this condition, dip in the sheets of tinfoil one by one, frequently taking them out until you find them a.s.sume a golden shade, when you will again fix them on the wooden board and apply a coat of varnish as before; when dry you will have sheets of tinfoil that you can use as you wish in your work...."[20]

[20] _Diversarum artium schedula_, Book 1. Chapters 21 and 36.

Although it may not be possible for an amateur, incompletely equipped with the necessary implements, to reproduce the marvellous work of a byegone age, there are still many methods of decoration for him to attempt which will be equally attractive in modern surroundings.

NOTE

SOME EXTRACTS FROM THE REPORT OF THE COMMITTEE ON LEATHER FOR BOOKBINDING, APPOINTED BY THE COUNCIL OF THE SOCIETY OF ARTS, FEBRUARY, 1900.

"This Committee met for the first time on May 3, 1900.... Its first step was to appoint two Sub-Committees from amongst its members. The first of these was to visit a selected number of libraries, and to ascertain the comparative durability of the various bookbinding leathers used at different periods and preserved under different conditions.... The second ... was appointed to deal with the scientific side of the matter, to ascertain the cause of any deterioration noticed, and, if possible, to suggest methods for its prevention in the future....

"The first step taken by the (first) Sub-Committee was to visit a number of libraries, including that of the British Museum, the Bodleian Library, Oxford, the University Library, Cambridge, the libraries of the Athenaeum Club, of the Patent Office and of the Chemical Society, also the valuable private library of Mr. Huth....

"As regards the common belief that modern binding leather does decay prematurely, the Sub-Committee satisfied themselves that books bound during the last eighty or hundred years showed far greater evidence of deterioration than those of an earlier date. Many recent bindings showed evidence of decay after so short a period as ten, or even five years. The Sub-Committee came to the conclusion that there is ample justification for the general complaint that modern leather is not so durable as that formerly used. To fix the date of the commencement of this deterioration was a difficult matter; but they came to the conclusion that while leather of all periods showed some signs of decay, the deterioration becomes more general on books bound after 1830, while some leathers seem to be generally good until about 1860, after which date nearly all leathers seem to get worse. The deterioration of calf bindings at the latter end of the nineteenth century may be attributed as much to the excessive thinness as to the poor quality of the material.

"With regard to the conditions under which books are kept, ventilation, lighting, heating, etc., the Committee were satisfied that in libraries where there was no artificial light used, and where the ventilation was good, the bindings were generally in a better state than elsewhere. Where gas is used the bindings are in the worst state noticed, especially on the higher shelves.... Daylight and still more direct sunlight, has a disintegrating effect on leather....

"As to the suitability of various leathers, the Sub-Committee came to the conclusion that of the old leathers (fifteenth and sixteenth century), white pigskin, probably alum tanned, is the most durable, but its excessive hardness and want of flexibility renders this leather unsuitable for most modern work. Old brown calf has lasted fairly well, but loses its flexibility, and becomes stiff and brittle when exposed to light and air.

Some of the white tawed skins of the fifteenth and sixteenth century, other than white pigskin, and probably deerskin, have lasted very well.

Some fifteenth and sixteenth century sheepskin bindings have remained soft and flexible, but the surface is soft and usually much damaged by friction. Vellum seems to have lasted fairly well, but is easily influenced by atmospheric changes, and is much affected by light. Early specimens of red morocco from the sixteenth to the end of the eighteenth century were found in good condition, and of all the leathers noticed, this seems to be the least affected by the various conditions to which it had been subjected. In the opinion of the Committee, most of this leather has been tanned with sumach or some closely allied tanning material.

Morocco bindings earlier than 1860 were generally found to be in fairly good condition, but morocco after that date seems to be much less reliable, and in many cases has become utterly rotten. During the latter part of the eighteenth century it became customary to pare down calf until it was as thin as paper. Since about 1830 hardly any really sound calf seems to have been used, as, whether thick or thin, it appears generally to have perished. Sheepskin bindings of the early part of the century are many of them still in good condition. Since about 1860 sheepskin as sheepskin is hardly to be found. Sheepskins are grained in imitation of other leathers and these imitation-grained leathers are generally found to be in a worse condition than any of the other bindings, except, perhaps, some of the very thin calf skin. Undyed modern pigskin seems to last well, but some coloured pigskin bindings had entirely perished. Modern leathers dyed with the aid of sulphuric acid are all to be condemned. In nearly every case Russia leather was found to have become rotten, at least in bindings of the last fifty years....

"The work of the second Sub-Committee, which was composed of chemists specially conversant with the treatment of leather, was directed specially to the elucidation of the following points; an investigation of the nature of the decay of leather used for bookbinding; an examination of the causes which produced this decay; a research into the best methods of preparing leather for bookbinding; and a consideration of the points required to be dealt with in the preservation of books....

"The Sub-Committee made a number of tests and a.n.a.lyses of samples of decayed leather bookbindings, as well as of leathers used for binding. The Committee found that the most prevalent decay was what they termed a red decay, and this they think may be differentiated into old and new, the old red decay being noticeable up to about 1830, and the new decay since that date. In the old decay the leather becomes hard and brittle, the surface not being easily abraded by friction. The older form is specially noticed in calf-bound books, tanned presumably with oak bark. The new form affects nearly all leathers, and, in extreme cases, seems absolutely to destroy the fibres. Another form of deterioration, more noticeable in the newer books, renders the grain of the leather liable to peel off when exposed to the slightest friction. This is the most common form of decay noted in the most recent leathers. In nearly all samples of Russia leather, a very violent form of red decay was noticed. In many cases the leather was found to be absolutely rotten in all parts exposed to light and air....

"An extensive series of experiments was carried out with a view of determining the causes of the decay of bindings. The Sub-Committee find that this is caused by both mechanical and by chemical influences. Of the latter some are due to the mistakes of the leather manufacturer and the bookbinder, others to the want of ventilation, and to improper heating and lighting of libraries. In some cases inferior leathers are finished (by methods in themselves injurious) so as to imitate the better cla.s.s leathers, and of course, where these are used, durability cannot be expected. But in the main, the injury for which the manufacturer and the bookbinder are responsible must be attributed rather to ignorance of the effect of the means employed to give the leather the outward qualities required for binding, than to the intentional production of an inferior article....

"We are of opinion that no special skin can be condemned in its original condition, although goat, seal, pig, and calf are probably superior in strength of texture to sheep. Sheepskins are, however, equally resistant to chemical agencies, and being naturally soft and flexible, are extremely suitable for use for purposes where they are not much exposed to mechanical wear.

"Fresh market skins, dry skins, or wet salted skins are much to be preferred to those known as 'drysalted,' since the crystallization of the salt which takes place in the drysalting process, tends to weaken the structural fibre of the pelt. No tainted or putrefied skins, even if only slightly affected, are suitable for the manufacture of bookbinding leather, both for the same reason, and because the weakness of grain so produced leads to uneven dyeing.

"In the soaking of skins we would strongly condemn the use of old putrid soaks, or the addition of salt to the soaks to a.s.sist in the softening, as both methods weaken the skin. ... Violent mechanical treatment such as 'stocking' is injurious....

"The liming should be done in mellow, weak limes. Old limes smelling strongly of ammonia, and containing large quant.i.ties of bacteriological products, must be avoided....

"Special care should be taken with regard to the beamhouse work after unhairing and fles.h.i.+ng, as, by excessive or unsound puering and drenching of the skins, their whole natural strength is frequently destroyed....

Great damage is frequently caused by the use of foul puers or foul bates, in which putrefaction has taken place.

"Pure sumach is the tannage we would most strongly recommend for high cla.s.s bookbinding....

"The tannage of bookbinding leathers must be a mellow one, and must not be carried too far, as we have found in many cases the cause of decay in tanned leather has been the fact that the leather was overloaded with tannin. Tanning has throughout a hardening effect on the leather fibre, which, if pushed too far, ends in brittleness and loss of tenacity....

"We must absolutely condemn the use of any but mild vegetable acids in souring or scouring the leather, or in the dye bath, and as far as possible would avoid the use of acids and alkalis on tanned leather, both being equally injurious.

"It has been shown by careful experiment, that even a minute quant.i.ty of sulphuric acid used in the dye bath to liberate the colour, is at once absorbed by the leather, and that no amount of subsequent was.h.i.+ng will remove it. In a very large proportion of cases, the decay of modern sumach-tanned leather has been due to the sulphuric acid used in the dye bath, and retained in the skin....

"We ... advise that the glazing of skins by friction in a damp 'seasoned'

condition should be avoided.

"The use of nitric acid as a preparation for glazing is absolutely destructive....

"The use of oxalic acid for was.h.i.+ng backs of books, or of leather for bookbinding, is fatal to their durability....

"The sprinkling of leather with ferrous sulphate (green vitriol), either for the production of 'sprinkled' calf or 'tree' calf, must be most strongly condemned, as the iron combines with and destroys the tan in the leather, and free sulphuric acid is liberated which is still more destructive....

"The stretching of leather tightly over books in a wet condition ...

should be strongly condemned....

"It is shown conclusively that the catechol tannins, which include turwar, quebracho, hemlock and larch barks, and gambier, are unsuitable for bookbinding leathers where durability is expected, and that sumach yields a much more permanent leather, while myrobalans occupy an intermediate place, but nearly approaching sumach. It is unfortunate that ca.s.sia bark, which is the tanning material employed for East Indian sheep and goat skins, should have proved so unreliable, since these leathers have been largely used in bookbinding without suspicion, and are in other respects a cheap and good article. With regard to sumach leathers themselves, it is possible that some of the darkening noticed may be due to the presence of adulterants, such as pistacia leaves, in the sumach used, as it is almost impracticable to obtain absolutely pure sumach, and the pistacia tannin is allied to that of the ca.s.sia.

"Of all the influences to which books are exposed in libraries, gas fumes--no doubt because of the sulphuric and sulphurous acid which they contain--are shown to be the most injurious, but light and especially direct sunlight and hot air, are shown to possess deleterious influences which had scarcely been suspected previously, and the importance of moderate temperature and thorough ventilation of libraries cannot be too much insisted on."