A Manual of Mending and Repairing; With Diagrams

by Charles Godfrey Leland

INTRODUCTION

The author of this work modestly trusts that all who read it with care will admit that in it he has distinctly shown that mending or repairing, which has hitherto been regarded as a mere adjunct to other arts, is really an art by itself, if not a science, since it is based on chemical and other principles, which admit of extensive application and general combination. It has its laws—a fact which has never been hinted at by any writer, since all recipes for restoration in existence are each singly inventions made to suit certain cases. This work has been conceived on a different principle.

A thorough knowledge of this art of repairing, mending, or restoring various objects is of very great value, since there is no household in which it is not often called into requisition. In the kitchen or drawing-room, in the library and nursery, there are daily breakages, of which a large and needless proportion are losses, simply because such a man as a general mender, who is accomplished in all branches of the art, does not exist. And, what is more, it is equally true that no one has ever realised to what a vast extent mending and saving may be carried, with a little expenditure of time, practice, and money, by any intelligent person who will devote serious attention to it. Within a comparatively few years discoveries in science or in nature have enlarged the ability of the mender to an extraordinary extent—I need only mention the applications now made with silicate of soda, celluloid, gutta percha, and glycerine to confirm what I say—so largely, indeed, that only the accomplished technologist and chemist is really aware of what can be done in general repairing compared to what was possible only a few years ago. I believe that there are few thoroughly practical persons (and, I may add, few who take an interest in art in any form, or even in books) who will read this work without deep interest, and without acquiring information of such value that in comparison to it the cost of the book will seem a trifle.

Though mending or restoring is a subject which in some form comes home to and concerns everybody, and which it is assuredly everybody’s interest to understand, this is, I believe, the first book in which its application to a great variety of wants has been made, and that in such a clearly co-ordinated manner, and according to such a simple principle, that whoever reads it can have no difficulty in mending any object, even though it be not described here. In all works of the kind which I have seen the recipes for repairing have been given simply according to their subjects, without any view to general principles of application, and a great proportion of these were in turn simply copied from old books of miscellaneous “receipts,” or newspapers in which every so-called new discovery is announced as infallible, or as if it had been tried and tested to perfection. That I have not recklessly accumulated in this fashion all kinds of recipes to fill my pages will appear very plainly to every chemist or technologist, who will perceive that, proceeding from a comprehensive table of generally recognised and long-tested bases of cements, I have given deductions and combinations scientifically agreeing with their laws and with experiment. The true object of giving a great number of recipes has not been solely or simply to supply the house-keeper or mechanic with instructions for certain repairs, but also to suggest to the technologist and inventor new ideas and applications. Thus, when we know that given proportions of zinc in powder, silicate of soda, and chalk form a strong cement, resembling zinc, it is as well to suggest that this may be varied by employing other metals and substances, such as bronze-powders and mineral oxides, to be always preceded by a little experiment. I venture to say that any intelligent person who masters this work can, on this hint, make for himself innumerable inventions; and I am sure that there is not the editor of a single technological journal who will not testify to the fact that every year a great many patents are taken out and fortunes made from recipes which are neither so scientifically combined nor practically useful as those which I here give. That there are fortunes still to be made is abundantly proved by the fact that there are very few people, comparatively speaking, who know where to get or how to make waterproof glue, or how to mend with it, neatly and durably, shoes, umbrellas, and many rents in garments; how to unite a broken strap; mend, by felting, torn hats; rehabilitate perfectly worm-eaten and torn-away paper; restore decayed broken wood; or mend, in fact, anything except with common glue or mucilage—both of which soon give way and crack or melt. So long as such general ignorance prevails, just so long there will be an opportunity for the inventor to make and sell cements, and for the repairer to find employment.

I call special attention to the fact that this book contains no merely traditional, untested recipes which have been simply transferred from one Housekeeper’s Manual to another for generations. Where I have not been guided by my own personal experience—which is, I venture to say, not very limited—I have either followed truly scientific works, such as the three hundred volumes of the Chemical-Technical Library of A. Hartleben; or, when citing from older authors, have invariably given recipes which agree with the principles advanced by modern analysts and inventors. And though not a professor of chemistry, yet, as I studied it and natural philosophy in my youth under Leopold Gmelin, L. Passelt, and Professor Joseph Henry, I trust that I have been sufficiently qualified to avoid errors in what I have written. In short, that I have not recklessly accumulated every recipe which I could find, and that what I give are really trustworthy, will appear plainly to the chemist or technologist, who will perceive that, proceeding from a given table of generally recognised and long-tested bases of cements, &c., I have then given deductions and combinations scientifically agreeing with their laws and with experiment. My book is not a pièce de manufacture, or of hack-work, but one which is the result of many years of practical experience in the minor arts and industries, on which subject alone I have published twenty-two works, without including pamphlets, lectures, and at least one hundred letters or articles in leading magazines and newspapers. There is, in short, very little mending or making described in this book which I have not at one time or other personally effected, having had all my life a passion for mending and restoring all kinds of objects, and that scientifically and thoroughly.

As I have observed, there is in every household continual breakage of many kinds—“or of the rending which cries for mending”—it is a matter of some importance that some one in the family should pay special attention to such matters. How often have I seen very valuable objects stuck together—anyhow and clumsily—with putty, wafers, sealing-wax, glue, flour-paste, or anything which will “hold” for a time, when a perfect cure might have just as well been effected had the proper recipe been taken to the first chemist. This is equally true as regards taking ink or stains out of garments, or repairing the latter perfectly, or mending shoes or indiarubber cloth, or felting worn hats and many other articles, all of which are treated of in this work.

It is true that everybody is not naturally ingenious, or clever, or gifted, but all may become skilful menders if they will duly consider the subject (which requires no hard study) and experiment on it a little. And here I would seriously address a few words to all who are interested in education. There is a certain faculty which may be called constructiveness, which is nearly allied to invention, and which is a marvellous developer in all children of quickness of perception, thought, or intellect. It is the art of using the fingers to make or manipulate, in any way; it exists in every human being, and it may be brought out to an extraordinary degree in the young, as has been fully tested and proved. Now, if we take two children of the same age, sex, and capacity, both going to the same school and pursuing the same studies, and if one of the two devotes from two to four hours a week to an industrial art class (i.e., studying simple original design, easy wood-carving, repoussé, embroidery, &c.), it will be found—as it has been by very extensive experiment—that the latter child will at the end of the year excel the former in all branches of learning; that is to say, in arithmetic or geography, so greatly does ingenuity proceed from the fingers to the brain. Now, mending is so nearly allied to all the minor or mechanical arts, it enters into them so closely, that it in a manner belongs to and is an introduction to them all. Like them, it stimulates invention or ingenuity, and is perhaps of far greater practical utility or direct use. Boys and girls learn very willingly how to mend, and, from a long experience in teaching them, I should say that a class with experiments and practical instruction in what is given in this book should take precedence of all carpentry, metal-work, joining, leather-work, or any other branches whatever. For it is easier than any of them, and it is of far more general utility, as the following pages clearly show. Such teaching would cost next to nothing for outfit, and would be the best introduction to technical education of all kinds.

There is an immense amount of breakage in this world, yet, as a French writer on the subject observes, there are more great artists than good menders; the latter being so extremely rare that proofs of it are seen in bungling restorations in every museum in Europe, and in the almost impossibility of finding (out of Italy) men who can perfectly mend first-class ceramic ware. We see this ignorance in reproductions of delicate ivory ware coarsely cast in gypsum, and in a vast rejection and destruction of antiquities in wood, stone, or ceramic ware, simply because they are most ignorantly supposed to be beyond repair when they might, with proper knowledge, be very easily and cheaply restored, to great profit. And if the reader will visit the “dead rooms” of any museum in Europe and then study this book, he will find ample confirmation of what I say.

And here I would mention that every collector or owner of any kind of works of art, of bric-à-brac, or curiosities, who will master the art of mending, can find an illimitable field for picking up bargains in almost every shop of antiquities in Europe, especially in the smaller or humbler kind. For it is very far from being true that these dealers know “how to mend everything;” on the contrary, I have often found them very ignorant indeed of mending, and have frequently instructed them in it. Thus I now have before me a “Holy Family” of the early sixteenth century, bas-relief in stamped leather, twelve inches by eight, for which I paid two francs, but which I might have had for one, it being utterly dilapidated, and apparently of no value. In two or three hours I restored it perfectly, and it would now sell for perhaps a hundred francs. By it hangs a “Madonna and Child,” painted on a panel, gold ground, fourteenth century, which, including a very broad and remarkable old frame, I purchased both for twelve francs. The panel was warped like a sabre,

, the colour and gesso ground badly scaled away in many places. It was split in two pieces; in short, it appeared to be nearly worthless. Now it is in very good condition, and would be an ornament to any gallery. As regards repairing ceramic ware or china, glass, and porcelain, art has of late years made remarkable advances, this kind of mending being the most in requisition. As for old carved wood, no matter how badly broken it may be, eaten away by worms, or rotten, or even wanting large pieces, so long as its original form is evident, it can be very easily repaired or restored to all its original beauty and integrity, as I shall fully explain. In this alone there is a vast field for investment or money-making, because there are annually destroyed almost everywhere quantities of old wood-carvings; for, being badly worm-eaten, they are ignorantly supposed to be irreparable. The same may be said of ancient carved ivories, which are ready to drop at a touch into dust, as were those from Nineveh in the British Museum, yet which are now firm and clear. It is also true of the bindings of old books, many of marvellous beauty, whether of stamped leather, parchment, or carved. Even more interesting and curious is the repairing or restoring worm-eaten manuscripts or papers of any kind, or parchment, the easy process of filling the holes not being known to many bibliophiles. This art is becoming known in Germany, where it is not unusual to buy an old book for a mark, rebind it in hard old parchment, repair it generally for two or three, and then sell it, according to the subject, for several hundred or thousand per cent. profit.

It is greatly to be regretted that it is so little known, especially in England, that to repair a few holes or restore a little broken, crumbling carving it is not absolutely necessary to tear down an entire Gothic church and build a new one, as is so very generally the case. There is no stone-work, however dilapidated it may be, which cannot be mended very perfectly, and that in almost all cases with a material which sets even harder than the original, as was perfectly shown at the Paris Exhibition of 1889. Dilapidated stone carved work, of all ages and kinds, which could be perfectly restored to a degree which even very few artists suspect, abounds in Italy, where it can be purchased for a song. The song, it is true, is generally sung to a small silver accompaniment, but the purchaser may make it golden for himself. For very few know how to restore a knocked-off nose so that the line of juncture be not visible; yet even this is possible, as I shall show. And I may here remark that in all the first galleries and museums of Europe, without one exception, there is abundant evidence to prove that, of all the arts, the one of repairing and restoring is the one least understood and most strangely neglected.

There is hardly a village so small that one man or woman could not make in it or eke out a living by repairing different objects. In towns and cities the demand for such work is much greater, for there ladies break expensive fans and jewellery, and children their dolls and toys, for mending of which the “rehabilitators” require “much moneys,” especially in the United States, where prices for anything out of the way are appalling.

I would therefore beg all people who are gifted with some small allowance of “ingenuity,” tact, art, or common-sense to consider that Mending or Restoring is a calling very easily learned by a little practice, and one by which a living can be made, even in its humblest branches, as is shown by the umbrella-menders and chair-caners in the streets. But common-sense teaches that any one who shall have mastered all that is explicitly set forth in this book ought certainly to be able to gain money, even largely; for, as I said, the opportunities of purchasing dilapidated works of art, mending and selling them, are innumerable, and Restoration is as yet everywhere in its mere rudiments and very little practised. That which might be a very great general industry of vast utility, employing many thousands now idle, only exists in a hap-hazard, casual way, as dependent on other kinds of work. But to me it appears as a great art by itself, dependent on certain principles of general application. And when we consider what is generally wasted for want of proper knowledge of this great art, it seems to me to be but rational that if we had in London a school for teaching mending and restoring in all its branches as a trade, with a museum to show the public, probably to its great astonishment, what marvels can be wrought by renewing what is old, it would be of great service to the country at large. A very little reflection will convince the least visionary or most practical reader that what is wasted or annually destroyed of valuable old works, which cannot be replaced, because they are no longer manufactured, if restored, would form the basis of a great national industry. It has not as yet, however, entered into the head of any one to conceive this, simply because no one has ever been educated as a general restorer, but only in a secondary, supplementary, small way as a specialist, generally as a botcher. And I maintain, from no inconsiderable knowledge of the subject, that the best menders and restorers by far are those who understand the most branches of their calling. The reason for this is plain; it is because a repairer, when he comes to some unforeseen difficulty—for example, in mending china—and finds the cements used are not exactly applicable, he will, if sensible, think of some other adhesive used in other kinds of work, or other combinations or appliances.

I go so far as to say that an exhibition of specimens showing all that can be done in mending and restoration in ceramic art, leather, carved stone, books, carved and wrought wood, castings, metal, furniture, fans, and toys, would probably serve as sufficient beginning to establish classes and a school. The objects should, when possible, be accompanied by a duplicate or photograph showing the condition they were in before restoration, on the principle of the picture-cleaners, who amaze the public with such startling contrasts of dirt and splendour.

How this can all be done will be found in this book, which I venture to suggest will often be found useful in every family, or wherever “things” are broken and worn. For the collector of curiosities who would willingly pick up bargains, I seriously and earnestly commend it as a vade mecum by means of which he may literally make money in any shop. For, as I have already said, strange as it may seem, the small dealers in bric-à-brac are generally very ignorant of all the curious secrets of restoration, or else they have no time or means to attend to such work. Again, if the collector has learned what I here teach, he will often detect restoration allied to forgery in expensive antiques, guaranteed to be perfect. It has been well observed by M. Ris-Paquot, in his valuable work, L’Art de restaurer soi-même les Faïences et Porcelaines, that it often happens, most unfortunately, that precious relics whose value is immense, such as the Italian faïences and those of Palissy or Henri II., come to collections in such a condition, so pitifully injured, that de visu we cannot buy them because we know of nobody who can actually restore them, and because this delicate work requires so much special knowledge. Add to this, that their great value and rarity disincline us to trust to the first-comer, or general workman, treasures which he might utterly ruin by clumsiness or ignorance.

I may add that I seldom walk out in Florence without seeing old worn faïences for sale for a mere trifle which with a little retouching, gilding, and firing could be made quite valuable. In such instances there need be no complaint of destroying the venerable effect and value of antiquity. In them antique material may be legitimately employed as a basis for newer work, especially when it is broken away, worn down to the core, or full of holes. Now, with what this book teaches in his mind, the artist or tourist will very soon realise, if he be at all ingenious, or can avail himself of the aid of some friend who has even a very slight knowledge of art, that he can at a slight outlay purchase objects which will become very valuable when afterwards restored at home.

As I can imagine no head of a family, and no dealer in miscellaneous works of art or any small wares, no provider of furniture or furnisher, to whom this work will not be a most acceptable gift, so I am very confident that every traveller who has trunks to mend or broken straps to join, and every emigrant roughing it in the forests or the bush of Australia or Canada, may learn from it many useful devices, and the fact that with nothing more than a small tin of liquid glue and another of indiarubber he can effect more than could be imagined by any one who has not studied the subject. On this I speak not without experience, having found that, both as a soldier and a traveller in the Wild West of America, my knowledge of mending was of great use to my friends as well as myself. A perusal of the Index of what is here given will satisfy the reader that this manual is in fact a vade mecum for almost all sorts and conditions of men and women, and that there are none who would not be thankful for it.

A friend adds to these remarks the suggestion that this work may properly be included among the presents to a bride as an aid to housekeeping; and it will probably be admitted that it would prove quite as useful as many of the gifts which are usually bestowed on such occasions.

I have truly said that, while breaking and decay are universal, there are literally nowhere any generally accomplished repairers—that is to say, experts who know and can practise even what is set forth in this book. Certain menders of broken china there are, of whom the great authority on fictile restoration, Ris-Pasquot, declares that none can be trusted with anything valuable. There are so few needle-women who can sew up a rent perfectly that a lady “to the manor born” paid in Rome two pounds, or fifty lire, for being taught the stitch, described in this book, by which it can be done. That it was a great secret to an expert and accomplished needle-woman proves that it cannot be generally known. A house-furnisher in London doing a large business once explained to me with manifest pride how he had, by dint of persuasion and treating, obtained from another what is really one of the simplest recipes for restoring a brown stain. All of this being true, it is apparent enough that any accomplished mender and restorer, lady or gentleman, can hardly fail to make a living by the art; and I sincerely believe that it is the simple truth that it is set forth in the following pages so fully and clearly that any one who will make the experiment can learn from it how to make a living. This is effectively, in all its fulness, a new art and a new calling, and it is time that it were established.

It is a great mistake to suppose that manufacturers are necessarily good menders of what they make. I have found, as have my readers, that it is not the great watchmaker who oversees the production of thousands of watches to whom a watch can be most safely trusted for rehabilitation. For, in nine cases out of ten, it is some extremely humble brother of the craft, who does nothing but mend in a small shop, who restores your chronometer most admirably. The same is true as regards trunks anywhere out of England, since in Germany and France anything of the kind is invariably botched with incredible want of skill. This runs through most trades; for which reason I believe that a really well-accomplished general mender, earnestly devoted to the calling in every detail and resolved to be perfect in it, could ere long repair better than most manufacturers, since the latter, in these days, all work by machinery or by vast subdivision of labour, and not, so to speak, by hand. But all repairing must be by hand. We can make every detail of a watch or of a gun by machinery, but the machine cannot mend it when broken, much less a clock or a pistol!

The value of this book will appear to any one who knows how little really good repairing there is in Europe. Since writing the foregoing pages I have gone through the galleries of the Vatican and many other museums, and been amazed at the coarse, ignorant, and bungling manner in which the great majority of antique statues and other objects of immense value have been mended up. There is in most cases no pretence whatever to conceal the lines of repair, and when this has been attempted it has failed through ignorance of recipes and instructions which may be found in this work.

A MANUAL OF
MENDING AND REPAIRING

MATERIALS USED IN MENDING

“There are full many admirable and practical recipes (Hausmitteln), which are often known only in certain families.”—Die Natürliche Magie. By Johann C. Wiegleb, 1782.

The art of mending or of repairing may be broadly stated as being effected, firstly, by mechanical processes, such as those employed by carpenters in nailing and joining, in embroidery with the needle, and in metal-work with clumps, or soldering; and, secondly, by chemical means. The latter consist of cements and adhesives, which are, however, effectively the same thing. This glue, or gum, is an adhesive or sticker; that is, a simple substance which causes two objects to adhere. The same, when combined with powder of chalk or glass, would be a Cement. This latter term is again applied somewhat generally and loosely by many, not only to all adhesives, but also more correctly to all soft substances which harden, such as Portland cement, mortar, and putty, and which are often used by themselves to form objects, such as “bricks” and castings; but these latter, having also the quality of acting as adhesives or stickers, are naturally regarded as being the same.

As will be speedily observed in the great number of recipes for mending which will be given in this book, there are many which occur frequently in different combinations; therefore it will be advisable and indispensable for those who wish to master mending as an art to indicate these as a basis.

As Sigmund Lehner has observed in his valuable work on Die Kitte- und Klebemittel, there have been such vast numbers of recipes published of late years for adhesives in various technological works, that the combination of the usual materials depends almost on the judgment of the experimenter, and every practical operator will soon learn to make inventions of his own. These materials, according to Stohmann, may be classified as follows:—

I.	Those in which Oil is the basis.
II.	Resin or pitch.
III.	Caoutchouc (indiarubber) or gutta-percha.
IV.	Gum or starch.
V.	Lime and chalk.

Lehner extends the list as follows into adhesives, or cements:—

I.	For glass and porcelain in every form.
II.	For metals not exposed to changes of temperature.
III.	For stoves and furnaces, or objects exposed to heat.
IV.	For chemical apparatus and objects exposed to corrosive liquids.
V.	Luting or cements, to protect glass or porcelain vessels from the action of fire.
VI.	Cements for microscopic preparations, for filling teeth and similar work.
VII.	Those for special objects, such as are made of tortoise-shell, meerschaum (ivory), &c.

Oils are divided into those (such as olive) which never become hard, and the linseed, which in time dries into a substance like gum. The latter combined with a great variety of mineral substances, such as plumbago, calcined lime, magnesia, chalk, red oxide of iron, soapstone, or with varnishes, forms insoluble “soaps,” which, as cements, resist water. They require a long time to set or become hard.

Resins and Gums include a great number of substances, such as resin or hard pitch, which is distilled from pine-trees; shellac, mastic, elemi, copal, kauri gum, amber, gum arabic, dextrine made from flour, the gum of the peach and cherry, and of many other trees. To these may be added frankincense and tragacanth, which is less an adhesive than a stiffener and dresser. Gums are generally rather brittle; this is remedied by combination with oily substances, volatile oils, or caoutchouc. With these gums Lehner includes asphaltum. The defect of such adhesives is, as he also remarks, that they will not resist high temperatures. This, however, will apply to most objects.

Varnish.—This belongs properly to the gums, but is technically regarded as a separate material. It is gum in solution in turpentine or spirits. For details vide Die Fabrikation der Copal- Terpentinöl und Spiritus-Lacke, by L. E. Andés; Leipzig, price 5 m. 40 pf.

Caoutchouc and Gutta-Percha are gums which when hard are still elastic, and resist the action of water. I have read that a perfect imitation or substitute for them has been made of turpentine, but have not seen it, though I have met with glue made with oil and turpentine, which very much resembled them in elasticity or flexibility. Reduced to a liquid form with ether, benzine, &c., these gums can be kept in a liquid state for a long time, and then hardened in any form by exposure to the air. They enter into a very great variety of cements, such as are meant to be tough or waterproof. Indiarubber is, on the whole, the best, and gutta-percha the cheapest, for cements.

Glue.—This is made, by boiling, from horns and bones; it is essentially the same as gelatine. It is the most generally known of all adhesives, and may be modified by certain admixtures to suit almost any substance. It has the peculiarity that it must always be boiled in a balneum mariæ, or in a kettle in hot water in another kettle. Its strength is vastly increased by admixture with nitric acid or strong vinegar. On the subject of glue in all its relations, the reader may consult Die Leim- und Gelatine-Fabrikation, or “The Manufacture of Glue and Gelatine,” by F. Dawidowsky; Vienna, price 3s.

Flour-Paste and Starch-Paste.—These mixtures, though generally used for weak work, such as to make papers adhere, can be very much strengthened by admixture with glue and gums. Combined with certain substances, such as paper, mineral powders, and alum, they, when submitted to pressure, become intensely hard, and resist not only water but heat, when not excessive. Also combined with varnishes they are decided resistants. Lehner speaks of them as if they were perishable in any condition.

Sturgeon’s Bladder.—With this the bladders of several kinds of fish are classed. Cut in small pieces and dissolved in spirits it makes a very strong adhesive, which is mixed with many others.

Lime is the most extensively used cement in the world. Combined with water it forms mortar. It is united with many substances, such as caseine or cheese, the white of eggs, and silicate of soda, to make powerful minor cements. On the subject of lime the practical technologist should consult Kalk und Luftmortel, by Dr. Herrmann Zwick; Vienna, A. Hartleben, price 3s., in which all details of the subject are given in full.

Eggs.—The yolk, and more particularly the white, of eggs is sometimes used as an adhesive, and it enters into many very excellent cements. For details as to the chemistry and technology of this material consult Die Fabrikationen von Albumin- und Eierkonserven (A Full Account of the Characteristics of all Egg Substances, the Fabrication of Egg, and Blood Albumen, &c.), by Karl Ruprecht; Vienna, A. Hartleben, price 2s. 3d.

Neutral Substances, or Binding Materials.—Almost any substance not easily soluble in water, and many which are, from common dust or earth, or clay, sand, chalk, powdered egg-shells, sawdust, shell-powder, &c., when combined with certain adhesives, form cements. This is sometimes due to chemical combination, but more frequently to mechanical union. In the latter case the adhesive clinging to every separate grain has the more points of adhesion, just as a man by clinging with both hands to two posts is harder to remove than if he held by one.

Caseine or Cheese.—This in several forms, but chiefly of curd in combination with several substances, but mostly with lime or borax, forms a very valuable cement. It is also combined with strong lye and silicate of soda. It must not, however, be too much depended on as a resistant to water or heat.

Blood, generally of oxen or cows, combined with lime, alum, and coal ashes, forms a solid and durable cement.

Glycerine forms the basis, with plumbago, &c., of several cements. Like oil, it renders glue flexible and partly waterproof. For chemical details on this subject, vide Das Glycerin, by J. W. Koppe, Leipzig.

Gypsum is combined with many substances to form cements, some of them of great and peculiar value.

Iron pulverised is the basis of a great number of very durable and strongly resistant cements.

Alum may be included among the bases, as it is very important in several compositions, forming a powerful chemical aid. It is excellent as aiding resistance to both moisture and heat. For an exhaustive work on alum consult Die Fabrikation des Alauns, &c., by Frederic Junemann, which should be carefully studied by all who work in cements.

There is a very great number of “indifferent” or minor aids to these, such as sugar, milk, honey, spirits of wine, water, ochre, galbanum, tannin, ammonia, feldspar, plumbago, sulphur, vinegar, salt, zinc (white), umber, bismuth, tin, cadmium, clay, ashes, &c., which are essential in certain combinations.

Dextrine, the gum of flour or starch, or Leiokom, much resembles gum-arabic, but is more brittle. Its adhesiveness depends somewhat on the manner in which it is dissolved. “It is,” says Lehner, “prepared by heating starch which has been moistened with nitric acid; also by warming paste with very much diluted sulphuric acid.”

Wax, including that of bees as well as paraffine, is used in repairs, and forms a part of several cements. On this subject consult Das Wachs, or “Wax and its Technical Applications,” by Ludwig Sedna; Leipzig, 2s. 6d.

Silicate of Soda, or Liquid Glass.—This is generally sold in the form of a very dense liquid. It is prepared by mixing quartz or flint sand with soda, or more rarely with potash. “It is,” says Lehner, “a glass which is distinguished from other glasses by being easily soluble in water. It is believed to be a very modern invention; but I have seen Venetian glasses of the fifteenth century which appeared to be painted with it, or something very similar; and I have found decided indications of a knowledge of it in two writers of the sixteenth century, Wolfgang Hildebrand and Van Helmont. According to Wagner, there are three kinds of liquid glass. By itself liquid glass can only be used for mending glass; but when combined with other substances, such as cement, calcined lime, or clay, or glass, in powder, it forms a body as hard as stone, or a double silicate, which is strongly resistant to chemical influences.” It occupies the first position as an adhesive for glass, nor is it surpassed as a cement in solid form. On this subject vide Wasserglas und Infusorienerde, &c., by Hermann Krätzer; Vienna, 3s.

Natural Cement, or Hydraulic Lime.—This is familiarly known to all readers as Portland cement, but it is found of different qualities in many countries, and is also made artificially. Certain mineral substances have the quality when powdered and combined with water of setting hard as stone; hence the name hydraulic. I have seen at Budapest articles of Portland cement made in Hungary which equalled in appearance fine black slate or marble, and, while much less brittle, were indeed in every respect more durable and resistant to exposure. These artificial cements can be largely incorporated with indifferent substances, such as sand; they, however, require intense baking, and may in consequence be regarded as a kind of fictile ware.

Portland cement is very thoroughly treated in Hydraulischer Kalk und Portland Cement (in all their relations), by Dr. H. Zwick.

Tragacanth, though called a gum, is properly nothing of the kind, not being a true adhesive. It is the product of the Astragalus verus, a tree found in Asia. It swells out in water, and softens, but without dissolving. It is more of a glaze than a paste; hence it is used extensively by confectioners, bookbinders, or to stiffen laces. It enters, however, into the composition of several cements.

Bread may be classed as a material by itself, as it derives certain peculiar virtues from the yeast which causes its fermentation. With certain combinations it becomes wax-like, or hard, and may be used to advantage in many repairs as well as for modelling. It has the great advantage of being easily worked and always at hand.

Celluloid is treated of in this work under the head of Artificial Ivory. It is made from gun-cotton and camphor. For full information on this subject consult Das Celluloid, or “Celluloid, its Raw Materials, Manufacture, Peculiarities, and Technical Applications, &c.,” by Dr. Fr. Böckmann, Vienna and Leipzig.

Potatoes, peeled and mashed, and kept for thirty-six hours in a mixture of eight parts of sulphuric acid to a hundred of water, and then dried and pressed, form a white, hard substance very much like ivory, or, as one may say, like white boxwood. Lehner expresses his doubt as to whether artificial meerschaum pipes were ever made of this substance, but I have seen them, and can testify that they looked like meerschaum, and certainly were much harder than bruyere, or briar-wood. Whether they will “colour” I cannot say.

The principle by which potatoes, paper, and many other substances can be hardened like parchment or horn is curious. Potatoes consist of about seventy per cent. water and twenty-five per cent. of starch, the remainder being salts and cellulose, which forms cells surrounded by the grains of starch. “When such a substance is for some time brought into contact with diluted sulphuric acid, that which results is simply a contraction of the cells” (i.e., a hardening), “or a kind of parchmenting.” Thus soft paper is converted into parchment.

It is evident that chemistry is as yet in its infancy as regards the conversion of cellulose by acid into hard substances. Since cotton, paper, and potatoes all produce by this process different substances, it is probable that hundreds of organic, or at least vegetable, substances will all yield new forms.

There is a marked difference between paste made of starch or flour, each having its peculiar merits. The former is principally prepared from potatoes. To prepare the cement we mix it with a very little water, stirring it very thoroughly till it assumes a bluish appearance. A little more hot water is then added, and the mass left till an opal-like tinge indicates that it has formed. To this then add hot water ad libitum. As it is almost colourless in very thin coats, it is largely used to glaze and give body or weight to, and often to simply falsify, woven fabrics, which by its aid seem heavier. To increase this weight white lead and other substances are used.

To make the best flour-paste, flour should be kneaded in a bag under water till all the starch is washed away. What remains is a substance closely allied to caseine, or the white of egg. Combined with lime it forms a hard cement. A very slight admixture of carbolic acid (also oil of cloves) will keep paste from souring or decay. This acid has the property of destroying the growth of the minute vegetation which constitutes fermentation, just as other strong scents or perfumes are supposed to disinfect rooms, &c.

A very great number of other ingredients, such as the oxides of lead or zinc, manganese, baryta, sulphur, sal ammoniac, flint-sand, clay, salt, ochre, varnish, galbanum, or frankincense, enter into certain recipes, but those already given may be regarded as constituting by far the principal portion of all cements in ordinary use.