The Principles of Leather Manufacture
Please see the Transcriber’s Notes at the end of this text.
The cover image has been created for this doucument, and is placed in the public domain.
H. R. PROCTER, F.I.C. F.C.S.
PROFESSOR OF LEATHER INDUSTRIES AT THE YORKSHIRE COLLEGE, LEEDS;
PAST PRESIDENT OF THE INTERNATIONAL ASSOCIATION
OF LEATHER TRADES CHEMISTS
E. & F. N. SPON, Limited, 125 STRAND
SPON & CHAMBERLAIN, 123 LIBERTY STREET
PROFESSOR F. L. KNAPP
GEHEIMEN HOFRATH, DR. PHIL. AND DR. ING.
THE PIONEER OF SCIENTIFIC RESEARCH
IN LEATHER MANUFACTURE
The origin of the present work was an attempt to preparea second edition of the little Text-Book of Tanning whichthe Author published in 1885, and which has been long out ofprint. Though persevered in for years, the work was neverbrought to completion, partly owing to the constant pressure ofother duties, but still more to the rapid advances which havebeen made in our knowledge of the subject, and in the scientificthought which has been devoted to it. For his share in theinitiation of this work, much credit is due to Wilhelm Eitner,Director of the Imperial Royal Research Institute for LeatherIndustries in Vienna, but the advance he began has beenenergetically carried forward not only in Vienna, but in theTanning Schools and Research Institutes of Freiberg, Leeds,London, Liège, Copenhagen, Berlin and elsewhere, and to aless extent in private laboratories.
Under the pressure of this rapid growth, as it was impossibleto complete the work as a whole, the Author publishedan instalment dealing with the purely chemical side ofthe subject in 1898, under the title of the ‘Leather IndustriesLaboratory Book’; which has been translated into German,French and Italian, and of which the English edition is rapidlyapproaching exhaustion.
The present work, which should by right have preceded[viii]the Laboratory Book (and which frequently refers to it as“L.I.L.B.”), attempts to deal with the general scientific principlesof the industry, without describing in detail its practicalmethods (though incidentally many practical points are discussed).To complete the subject, a third volume ought to bewritten, giving working details of the various methods ofmanufacture; but apart from the difficulty of the subject, andthe weariness of “making many books,” the methods of tradeare so fluctuating, and dependent on temporary conditionsthat they have not the same permanent value as the record ofscientific advance.
As the present volume is intended to appeal both to thechemist and to the practical tanner, it must to a certain extentfail in both, since many matters are included which are alreadyfamiliar to the former, and it is to be feared, some, which mayprove difficult to the latter. For these and other imperfectionsthe Author claims the indulgence of his Readers.
The Author must here acknowledge his indebtedness toDr. Tom Guthrie and to Mr. A. B. Searle for assistance inwriting several of the chapters; to Dr. A. Turnbull and Mr.F. A. Blockey for much help in reading proofs and preparingthe MS. for the press; and to the many gentlemen who havefurnished or allowed him to use their blocks and drawings inillustration.
The Yorkshire College,
INTRODUCTORY AND HISTORICAL.
Primitive methods of leather manufacture — Use of leather by the ancients — Progressof leather manufacture in England — Methods of productionof leather — Vegetable tannages — Combination tannages — Use of aluminium,iron and chromium — Oil- and fat-leathers — Difficulties of scientifictreatmentPAGE 1
INTRODUCTORY SKETCH OF LEATHER MANUFACTURE.
The object of tanning — Washing and soaking — Removal of hair by liming — Unhairingby putrefaction — Unhairing and fleshing — Deliming — Bating,puering and drenching — The vegetable tanning process — Currying — Alum,chrome and chamois leathersPAGE 7
THE LIVING CELL.
The structure of cells — White blood-corpuscles — The yeast-cell — Epidermiscells — The building up of plantsPAGE 10
PUTREFACTION AND FERMENTATION.
The nature of ferments — Organised and unorganised ferments — Classificationof organised ferments — General properties of ferments — The alcoholicfermentation — The action of enzymes or unorganised ferments — Thedestruction of ferments by heat and antiseptics — The products offermentation — The fermentations of the tannery — Fermentation inbating and puering — Fermentation in the tanning liquors — Moulds and[x]mildews — Control of fermentationPAGE 15
ANTISEPTICS AND DISINFECTANTS.
Distinction of antiseptics and disinfectants — Lime — Sulphur dioxide — Manufactureof sulphuric acid — Bisulphites and metabisulphites — Boricacid and borates — Mercuric chloride — Mercuric iodide — Copper sulphate — Zincsalts — Arsenic — Fluorides — Phenol — Use of carbolic acid — Eudermin —Creasote — Creolin — Salicylicacid — Benzoic acid — Cresotinicacid — Anticalcium — “C.T.” bate — Naphthalene sulphonic acid —Naphthols — Hydronaphthol — Oxynaphthoicacid — Carbon disulphide — Formaldehyde — Triformol — Camphorand essential oilsPAGE 21
THE ORIGIN AND CURING OF HIDES AND SKINS.
Marking of hides — Fellmongering of sheep-skins — The use of salt — Saltingof packer hides — Brining — Dry-salting — Indian plaster cures — Analysisof salt-earths — Salt- and iron-stains — Drying of hides and skins — Damageby insects — The warble-fly — Damage by branding — CocklePAGE 33
STRUCTURE AND GROWTH OF SKIN.
Similarity of Mammalian skins — Development of skin — Structure of calf-skin — Theepidermis — The structure of hair — The sebaceous glands — Thedevelopment of hair — The hair-sheath — The hair-muscle — Thehyaline layer — The corium — Connective tissue — Fat cells — Stripedmuscle — Elastic fibres — The unhairing process — The sweating processPAGE 46
THE CHEMICAL CONSTITUENTS OF SKIN.
The keratin tissues — Production of gelatine from connective tissue — Analysesof hide and gelatine — Constitution of gelatine — Analysis and Reactionsof gelatine — Decomposition of gelatine — Reactions of gelatine — Chondrin — Coriin —Hide-albumin — “Acid”and “alkali” albumins — Egg-albumin — Vitellin — Casein — Keratins — Elasticfibres — Analytical methods — Kjeldahl[xi]processPAGE 56
THE PHYSICAL CHEMISTRY OF THE HIDE-FIBRE.
Causes of swelling and contraction — The essentials of the tanning process — Theconstitution of matter — The nature of molecules — Vapour-pressure — Surface-tension —Solution-pressures — Jellies — Crystals — Osmoticpressure — Electrolytic dissociation — Electrolysis — Reactions of ions — Absorptionof water by gelatine — Dehydration by alcohol — Action ofacids, alkalies and salts on gelatinous fibre — Physical explanation ofswelling — Action of acids on gelatine — Action of alkalies on gelatine — Effectof salt — The pickling processPAGE 73
WATER AS USED IN THE TANNERY.
Impurities of natural water — Hardness — Soap test — Temporary hardness — Clark’ssoftening process — Archbutt and Deeley’s softening apparatus — Otherappliances — Effect of temporary hardness in tanning and dyeing — Permanenthardness — Boiler scale — Mud — Iron — Alumina — Soda — Copper,lead, etc. — Sulphuric acid — Nitrates and Nitrites — Chlorine — Carbonicacid — Silicic acid — Effect of hardness on plumping — PeatywatersPAGE 93
SOAKING AND SOFTENING OF HIDES AND SKINS.
Washing of fresh hides — Danger of putrefaction — Soaking of salted hidesand skins — Soaking and softening of dry and dry-salted hides — Americanwash-wheel — Chemical methods — Difficulty of softening hides dried athigh temperaturePAGE 108
Methods of depilation — Sweating process — Liming — Sources of lime — Quicklime — Slakingof lime — Solubility of lime in water — Analysis of lime — “Available”lime — Action of lime on hide — Liming in pits — Suspensionlimes — Effect of warming limes — Quantity of lime required — The Buffalomethod — Action of old limes — Solution of hide substance by limes — Sodium[xii]and potassium hydrates — Payne and Pullman’s process — Alkalinecarbonates — Alkaline sulphides — Sodium sulphide — CalciumSulphydrate — Gas-lime — Tank-waste — Lufkin’s liming preparation — Bariumsulphydrate — Realgar, or red sulphide of arsenic — “Inoffensive”unhairing solution — Earp’s patent — Unhairing on the beam — Unhairingmachines — Vaughn machine — Leidgen machine — Unhairing in stocksand wash-wheel — Jones machine — Fleshing — Vaughn fleshing machine — RoundingPAGE 119
DELIMING, BATING, PUERING AND DRENCHING.
Methods of removing lime and reducing swelling — Use of acids — Lactic,acetic and formic acids — Boral — Sodium bisulphate — Boric (boracic)acid — Borax — “Pulling down” process — Use of ammonium chlorideand sulphate — Pickling solutions — Drenching with lactic acid — Metabisulphiteof soda — Washing out lime, French process — Nesbitt’sprocess — Use of carbonic acid — Carbolic acid — Cresotinic acid — Oxynaphthoicacid — “Anticalcium” — “Acrilene bating acid” — “C.T.Bate” — Use of sulphides and polysulphides — Babool pods — Bran-drenching — Batingand puering — Causes of bating effect — Pepsin — Trypsin,or Pancreatin — Wood’s researches — Erodin — Palmer’s experiments — Otherartificial bates — Relative effect of dog- and pigeon-dungbates — Analysis of dungs — “Scudding,” or “fine hairing” — Preservationand use of dungPAGE 152
ALUM TANNAGE, OR TAWING.
Nature of leather — Mineral tanning substances — Salts of aluminium — Alums — Aluminiumsulphate — Effect of salt in tawing — Basic alumina solutions — Tawingof skins for rugs — Calf-kid manufacture — Glove-kid — Greenleather and other combination tannagesPAGE 184
IRON AND CHROME TANNAGES.
Iron tannages — Chrome tannages — Chemistry of chromium compounds — Knapp’smethod of chrome tannage — Cavallin — Swan — Heinzerling — Hummel’simprovement — Schultz’s method — Theory of the two-bathprocess — Practical management of the two-bath process — Dennis’schrome tanning liquor — Procter’s liquors — Theory of basic process — Practicaluse of basic liquors — Washing and neutralisation — Effect ofsulphur on chrome leather — Bluebacking — Fat-liquoring — Dyeing of[xiii]chrome leather — Glazing and finishingPAGE 198
PRINCIPLES OF THE VEGETABLE TANNING PROCESSES.
Methods of sole-leather tanning — Finishing of sole-leather — Theory ofvegetable tannage — Deliming of sole-leather — “Mellowness” of liquors — Penetrationof tannage — Drying of sole-leather — Tanning of dressingleathers — Preparation for tannage — Avoidance of “bloom” — Tannageof moroccos and other skinsPAGE 220
COMBINATION OF VEGETABLE AND MINERAL TANNAGES.
Early combination tannages — Respective effect of mineral and vegetabletannages — Use of fat-liquor — Action of mineral and vegetable tanningmaterials on each other — Danish and Swedish glove leathers — Greenleathers — Making of fat-liquors — Chrome combinationsPAGE 236
VEGETABLE TANNING MATERIALS.
Distribution of tannin in plants — Structure of barks — Botanical list ofimportant tanning materialsPAGE 242
THE CHEMISTRY OF THE TANNINS.
Sources of tannins — General qualities of tannins — Chemical constitution — Catechol-and pyrogallol tannins — Catechins — Tendency of Catecholtannins to darken with light — “Physiological” and “pathological”tannins — Presence of mordant colouring mattersPAGE 294
THE SAMPLING AND ANALYSIS OF TANNING MATERIALS.
The International Association of Leather Trades Chemists — The AmericanOfficial Association of Agricultural Chemists — The sampling of material — Preparationof solution for analysis — Extraction of solid materials — Totalsoluble matter — Evaporations of solutions — The weighing ofresidues — The determination of non-tannins — The hide-powder filter[xiv]method — The hide-powder shake method —