The manufacture of leather: being a description of all of the processes for the tanning and tawing with bark, extracts, chrome and all modern tannages in general use ...

Preface

TO THE SECOND EDITION

After nearly two years spent in the thorough revision, and the almost re-writing of this book, necessary on account of the many improvements in the manufacture of leather, the time has come to prepare the preface.

The object which the author has kept constantly in view has been to supply his readers with practical and useful information upon such subjects as come within the scope of the book, and in as condensed a form as possible. He has given no space to mere theorizing, as he feels that he can be of greater use in setting forth good technical information, combined with suitable illustrations. The reader of a work of this character is necessarily looking for help in his particular field of industry, and is much better pleased to find the subject clearly expounded than to wade through pages of purely theoretical matter.

The tanner's trade, like most other trades, has in the past been followed and carried out by rule of thumb rather than by scientific guidance. But this is steadily and rapidly changing ; chemistry having become the handmaid of all the industries, the chemist is necessarily a part of the personnel of every large tannery, and in all departments of leather manufacture he is making his influence felt for good.

During the past fifteen years the leather industry of the United States has made greater strides than in all of the previous centuries of its existence. The chrome process has been introduced, and tanning extracts havecome into general use,

VI PREFACE TO THE SECOND EDITION.

and the world largely owes its progress, in these directions, to the United States. True, Germany led in the theoretical research regarding the use of chrome, but it remained for the United States to make this invention a practical success.

We are ever traveling onward, and while it may by some be considered that the duty of 15 per cent, on hides and calf-skins might be an impediment, it can readily be overcome by our superior machinery and skill, and thus will we be able still to hold our foreign trade.

While this industry has progressed from the simplest and most primitive to its present state, it is not yet perfect. The author would therefore admonish every manufacturer of leather to be on the lookout for all new improvements, and when found to be practicable to adopt them, as only in this way can he keep "up-to-date," and thus be saved from being relegated to the rear. It is much easier to go backward than to go forward.

He desires especially to acknowledge his indebtedness to the Shoe and Leather Reporter for much valuable data gathered from its columns, and to all other trade papers from which he has taken any matter, not specially acknowledged in the body of the book.

Charles Thomas Da,vis.

Washington, D. C, 605 Seventh Street, October i, 189J.

M

CHAPTER I. Water and Pumps

PAGE

Location of tanneries and currying shops in the United States ; Advantages of locations upon rivers and streams; Important position of water in tanning ; Most important admixtures of water and their influence in tanning I

Distinction of water as hard and soft ; Admixtures of spring and well water ...„......••• 2

Points to be considered in determining the qualities of water for tanning purposes ; Reasons for swelling or plumping hides intended for sole leather ........-■■■• 3

Temperature of the water used for preparing the hides ; Methods for determining the constituents of water . . 4

Process of determining the hardness of water by a soap solution . . 5

Determination of total hardness 6

Determination of permanent hardness ; Softening water ... 9

Use of borax for purifying water 10

Pumps ; Prominence of pumping machinery among the various branches of engineering ............ 12

Classes of pumps commonly used for raising water from wells ; Lifting or atmospheric pumps and their action ....... 13

Limit of height to which water can be raised from wells by common atmospheric pumps ........... 14

Importance of a uniform temperature of the water in the manufacture of waxed calf; The Pohle system of pumping water by compressed air 15

The Pohle Air Lift Plant at the works of the Henry Lang Co., Newark, N. J., described and illustrated 19

CHAPTER II. Animal Skin

Classes of raw products with which the tanner has to deal ; Structure of

the animal skin ; Composition of the epidermis 21

( vii )

viii CONTENTS.

PAGE

On what the quality of the leather -which can be produced from a skin

depends; A transverse section of the skin, described and illustrated . 22 Conversion of the connective tissue fibres into glue . . . .23 Behavior of skins under various conditions ; Chemical and morphological constitution of the skin 24

Preparation of coriin 25

Swelling influences of natural waters upon the coriin ; Effect of too

Preparation of connective-tissue substance ...... 27

Swelling influence of acids upon the skin fibres 28

CHAPTER III. Vegetable Tanning Materials

Rutea; Kino; Malabar or East Indian kino; Gambier ; Catechu or terra japonica . . . . . . . . . . . .29

Gall-nuts 30

Galls (Knoppern); Chinese gall-nuts; Rove; Sumach ; Sicilian sumach ; Italian sumach ........... 31

Spanish sumach ; Tyrol sumach ; French sumach ; Tezera sumach ;

American sumach ; Swedish sumach ; Valonia 32

Divi-divi ; Myrobalans ; Bublah ; Logwood ; Fustic . . . .33 Weld ; L,arch bark ; Fir bark ; Hemlock bark ; American hemlock extract ; Oak bark 34

Prof. Forbes on the value of canaigre tanning materials ; Quebracho . 36 Discovery of the valuable tanning properties of quebracho ; Home of the quebracho tree ......:.... 37

Prof. Eitner on the uses of quebracho ....... 38

Sample of leather tanued with quebracho extract; Analysis of quebracho ............. 39

Statistics of exports of quebracho from the Argentine Republic ; Statistics of the American export trade in sole leather to Germany ; Forests of quebracho trees in the Argentine Republic ..... 40

Advantages of the use of quebracho ; Process for using pure quebracho

wood for sole leather in Buenos Ayres ; First or coloring liquor . . 41 Second liquor ; Third liquor ; Method for employing quebracho with oak bark for sole leather in Europe ....... 42

Loss in export trade in sole leather of the United States . . . .43

Cost of quebracho bark ; Palmetto root ....... 44

Chestnut oak wood ; Walnut bark ; Iyombardy poplar bark ; Elm bark; Horse-chestnut bark ; Phyllocitannic acid ; iFsculotannic acid . . 45

CONTENTS. ix

PAGE

Horse-chestnut extract ; Willow bark ; Alder bark ; Beech bark ; Protacese barks ; Snouba bark (scorza rosa) ...... 46

Ratanky root ; Avens root ; Tormentil root ; Sassafras root ; Geranium Wallachianum ; Mesquite oak and live oak barks ; Mimosa . . 47

CHAPTER IV. Leaching ; The Barkometer ; Bark Mills ; Bark Conveyer ; The

Tan Press.

Cardinal points to be considered in leaching l . ..... 48

The gravity system generally employed by American tanners and extract makers ; Illustration of the most common way of leaching ; Absolute necessity of slow leaching ........ 49

General rule for the head leach ; The ideal leach 50

The most seriously defective system of leaching . . . . .51

Leach pumps of the Vaughn Machine Co., Peabody, Mass.; Regulation of the temperature of the liquors in leaching . . . .52

The problem of properly leaching bark ....... 53

How the difficulty of packing may be overcome ; Manner of pumping . 54 Taking advantage of the factor "percolation ;" Limit to the length of

the column in any one leach ; Advantage of ten or more leaches . 55 Temperature of the water or liquor on the tail leaches ; Check on the efficiency of the leaching ......... 56

Loss in tanning substance of the bark in the layaways; Use of the spent liquor from "rockers" on the tail leach ; Object of applying a mellow liquor, weak in tanning substance, to a green hide from the beam house .............. 57

System of leaching bark in use by the American Oak Leather Co., Cincinnati, Ohio ; Stephen Dow & Co., and F. C. Cottle & Son, and Beggs & Cobb's systems of leaching hemlock bark . . . .58

Preference for pumping leaches more frequently ; Flooding leaches ; Great attention paid to the grinding of bark ...... 59

Ledger account for each leach ; The Press-leach system . . . .60

The barkometer and its application ........ 62

Bark mills ; The earliest patent for a bark mill awarded to C. Foss . 63 A. Bull's patent ; Main object in grinding bark ; Fads in the bark business 64

Reform brought about by Dr. H. F. Starcke's analyses of " spent tan " . 65 Various constructions of bark mills ; Bark cutter (Jones' patent) made by the Vaughn Machine Co., Peabody, Mass. . . . . .66

Automatic knife grinder for the Jones patent bark cutter and other cutters ; Bark conveyer patented by Oliver A. Zane, of Peabody, Mass . 68 The tan press made by William F. Martin, Salem, Mass. . . .71

X CONTENTS.

CHAPTER V. Tanning Extracts

PAGE

Growth in the use of extracts ; Tanning extracts in common use in the United States ; Manufacture of tanning extract from the chestnut tree and chestnut oak tree 74

Concentration of the liquor in the vacuum pan 75

Preparation of hemlock extract ; Boiling point of water ; Similarity of the manufacture of tanning extracts to the process of extracting sugar. 76

Decolorization of the liquor before concentration ; Examination of tanning extracts 77

CHAPTER VI. Soaking and Softening

Process of soaking bides as recommended by a German tanner ; Soaking hides in wheels and in a water-pit or box . . . . .78

Preparation of hides and skins for soaking ...... 79

Treatment of foreign salted hides and skins, dry salted hides, kips, etc., and dried hides and skins 80

Reasons for the neglect by tanners of foreign hides and skins ; Necessity of the preparatory work being thorough . . . . .81

Usual mode of softening dry hides for sole leather ; Chemical soak ; Directions for working various kinds of hides ...... 82

Use of borax for softening water ; Use of pure water in the soaks . . 83

Time required for soaking calf-kid and light hides ; Softening ; Hide mills and their construction ; Softening mill in use by the morocco and kid tanners of Philadelphia, Penna. ...... 84

CHAPTER VII. Deputation or Unhairing

Definition of a depilatory ; Depilous skins ; Different methods for accomplishing depilation ; Preparation and properties of lime

Objections to the use of lime . . . . . . . . . .

Restoration of the suppleness to upper, morocco and other kinds of leather ; Bating ; Recapitulation of the inconveniences of the liming process ; Raising ...........

Primitive manner of removing the hair ; Necessity of properly prepar-

CONTENTS. XI

PAGE

ing the hides or skins for the beam house ; Proper condition of hides for limed stock ; Neglect of the work at the lime pits . . . .89

Proper treatment of calf-skins in the limes ; Replacement of lime in depilating by acid liquors .......... 90

Construction and arrangement of lime vats ; Preparation of a new vat ; Dead, weak and live vats ......... 91

Operation of raising ; Time employed for liming ; The power reel ; American practice of putting hides through the soaks and limes ; Impossibility of giving exact or arbitrary rules for liming and handling. 92 Arsenic and its use in lining of goat skins ; Economies and improvements in lining and bating ......... 98

Use of lime and dog-pure in the beam house ; Action of the lime ; Removal of grease in the lining of sheepskins . . . . .94

The disease known as itch and objection to scabby skins . . .95

The white itch and its cause 96

Depilating with sodium sulphide ; Prof. Fiebing on this subject . . 97 Method of using sodium sulphide in connection with lime . . .98 Enumeration of the advantages obtained by the use of sodium sulphide 99 On what the value of sodium sulphide as a depilatory depends ; John W. Stevenson on the sulphide of sodium process ..... 100

Method of using sulphide of sodium as a depilating agent . . . 102 Most striking effect of sulphide of sodium in the limes ; Explanation of the property of sulphide of sodium of bringing back the grain to its fresh, green state ........... 104

Summary of the good qualities of sulphide of sodium ; Undesirable qualities of sulphide of sodium ........ 105

Aging of alum-tawed glove-kid 106

Reasons why a green skin is fiat and unelastic as compared to well-tanned leather ; A German opinion on the use of sulphide of sodium 107 Main requisite demanded of a depilatory ; Arsenic as a depilatory . . 108 Combination of sulphide of arsenic with lime ; Action of sulphide of sodium and of sulphate of arsenic and lime ...... 109

Action of lime alone ; Rapidity of the action of arsenic-lime . . . 110 Comparison of results obtained by arsenic with those obtained by sulphide of sodium Ill

Constitution of the hide; Nature of the grain of the hide; Action of depilatories on the true skin and on the grain; Cause of the inner rottenness of leather 112

Effect of allowing putrefaction to progress; Selection of skins in the beam-house; Depilating with charcoal ....... 113

William Anderson's method of depilating with charcoal; Depilation with sulphide of barium; Foley's process ...... 114

Advantages of this process over the liming process 115

"Working-out and unhairing all kinds of hides and skins without limes, bate, drench or beaming — the Peirson-Moor process; Chemistry of depilatories 116 xii CONTENTS.

PAGE

Results of the analysis of liquor from an old, well-plunged lime pit 117

Proximate analysis of red arsenic ; Investigation of the part played by

red arsenic in the mixture of it with lime . . . . . .118

Investigation of the depilatory properties of calcium thioarsenite . . 119 Depilation by sweating; Villon's experiment and conclusions drawn

The "cold-sweat" process and the "warm-sweat" method; Cause of

"frieze;" "black spots " or "old grain;" Description of a building

for sweating hides and skins ......... 121

Care to be observed in sweating hides 124

Effect of the sweating process; Advisability of the sweating process for

imported hides 125

Method of sweating 126

Operation of the sweating process; The warm-sweating process . . 127 Sweating fresh hides . . . . . . . . . . .128

CHAPTER VIII. Unhairing and Freshing by Hand and Machinery

Interior view of the beam-house; The German form of beam and the unhairiug knife; Unhairing of hides and skins by the hand method 130

Injury to hires in unhairing; The "short-hair knife;" Beam work in France 133

Unhairing of slaughtered calf-skins fresh from the Paris market; Fleshing by the hand method; Fleshing knives described and illustrated 135

German, or spring fleshers; Operation of fleshing; The saw-tooth flesher, described and illustrated ......... 136

Turning steel described and illustrated; Going over the flesh-sides with the "worker" 137

Counter-fleshing; A sure hand required to do the fleshing of a calf-skin; Soaking hides after fleshing by the hand process ..... 138

Soaking hides in a steeping cistern after fleshing; How long should the hides soak after fleshing, and what indicates their readiness for scouring 139

Fleshing and unhairing by machinery; The Vaughn improved fleshing, unhairing and working-out machine, illustrated and described . . 140

The cylinders used with this machine, illustrated; Grinding lathe or cylinder and roll sharpening and turning- up machine made by the Vaughn Machine Co., described and illustrated 144

Unhairing machines ; Whitney's "Jumbo " unhairing machine . . 146

Whitney's patent combined unhairing, fleshing and working-out machine 147

Whitney's patent re-fleshing machine ....... 149

Practical success of the unhairing and fleshing machines. . . .151

CONTENTS. Xlll

CHAPTER IX. Bating

PAGE

Various terms applied to this process ; Reasons \vr13' the greatest risk in

any beam-house is that of bating ........ 153

Scientific investigation within recent times of the processes connected

with the tanner's art; Objections to the use of manure bate; Action of

Bran bate; Necessity of removing the lime or other alkaline depilatories

from hides and skins previously to tanning; Substitutes proposed and

patents covering processes for bating 155

C. T. Bate (coal-tar bate) invented by Peter S. Burns and Chas. S. Hull

and manufactured by the Martin Dennis Chrome Tannage Co.; Other

acids proposed for bating purposes ....... 156

" Borol;" P. Hauff's patent ; Manner of bating ; Suggestions regarding

the old form of manure bates; Bating high-limed goat skins . . 157 Fermentive action of the bate; Best time for fine-hairing; Best bate for

calf kid and sides; Borax and boracic acid as bates; Purpose of puring

light leathers 158

Method of puring; Consequence of leaving any lime in the stock . . 159 Treatment of hides intended for sole leather; Bating dressing leather in

the United States; Bate for sole leather 160

Universality of the practice of reducing the hide or skin and objections

to that practice ........... 161

Puring sole leathers; Inability of getting colors right in glove leathers

due to poor bating 162

Properties of dog excrements; Preparation of dog-pure; Theory of dung

Various substances employed as bates; Objections to the present method

of bating; Usual method of bating. . . . . . . . 164

England wheels for agitating the bate liquor; Scouring; Graining; Final

soaking before placing the hides in the ooze ...... 166

CHAPTER X. Handling and Plumping

Handling; Various methods of handling hides; Handling and transferring the sides by the medium of a revolving device, such as a reel . 167

Modes of connecting the sides; The hand reel; The rocker handler; Apparatus invented by U- C. England, described and illustrated . . 168

Paddle wheels for handling and vats in which they revolve t . . .170

Some European methods of handling; Handling the sides in the manuxiv CONTENTS.

PAGE facture of grain and split leather; Handling by means of a large revolving drum; Gorsline's apparatus for handling 172

Plumping; Plumping by means of sour liquor 173

Distillation of the sour liquors as proposed by H. J. Botchford . . 174 Plumping by means of sulphuric acid ; Introduction of this process by

David Mac Bride 1 75

Properties of sulphuric acid ......... 176

Plumping by means of acetic acid 177

Mineral acids for plumping; Lactic acid for plumping .... 178

Chapter XI. Laying-away

Action of tannin; Probability of leather not being a chemical combination of the animal substance with the tanning substance; Mr. Knapp's experiments in making leather without tanning elements . . . 179

Final step in the process of tanning heavy hides and sides; Laying away the stock , 181

Layers and periods for tanning the heaviest sole leather in this country; Laying away the packs in the manufacture of finer grades . . .182

Various methods of passing the liquor; Jack for raising whole hides up in the lay-away vats . . . . . . . . . .183

Float for whole hides ; Handling the sides in tanning heavy upper leather 184

CHAPTER XII. Stoning

Stoning-jack made by J. T. Freeman & Co., Woburn, Mass . . . 185

CHAPTER XIII. Splitting Leather

Perspective view of the cellar of ah upper leather tannery; Splitting machines; Splitting machine patented by Alpha Richardson; Early invention of Seth Boyden 186

Richardson's Union Splitting Machine; The Belt Knife Splitting Machine invented by Joseph F. Flanders and Jere A. Marden; Perspective view of, the Union Splitting Machine; Attachment patented by John A. Enos; Leather-splitting as generally practiced . . . 188

CONTENTS. XV

PAGE

Details of Enos's invention ......... 190

Leather-splitting machine embodying Enos's invention .... 191

Remedy of difficulties in splitting .....'.. 192

Hints for splitting with the Union Splitting Machine .... 193

The Belt Knife Leather Splitting Machine 194

Instructions in regard to splitting leather 198

Bassett's belt knife splitting machine; Improvement on grinder rigging

for belt knife splitting machines .....*.. 201 Removing the rubber roll from the Bassettt belt knife splitting machine 202

Robertson's grinding adjustment for belt knife splitting machines. . 203

CHAPTER XIV. Scouring

Treatment of the leather after it has been split; Tools used in the hand method of scouring leather ... ...... 208

Monk's scouring machine and the leathers on which it can be nsed . 209 Scouring and setting out machine built by the Vaughn Machine Co., Peabody, Mass 212

Chapter XV

Stuffing Leather ; Oils and Fats ; Testing Oils ; Water Proofing Leather.

Hand stuffing ; Tempering upper leather ; When the hand process of stuffing leather is accomplished ; Objections to the hand method of stuffing ............. 215

Drum stuffing; The best material to use in stuffing; Heating the drum . 216 Filling the drum; Removing the goods; Setting the goods; Stoning . 217

Reed and Winchester's stuffing drum 218

Improvement in tramping drums invented by Dr. Friederich Knapp . 220 Freeman's stuffing drum; Curriers' oils and greases; Definition of oils . 221 Three different classes of bodies embraced in the name oil; Fixed or fatty oils; Volatile and essential oils; Mineral oils; Properties of fats . 222

Most common and abundant fats; Cod oil 223

Adulterants of cod oil; Chief seats of the cod fishery; Classification for cod liver oil; Chemical and physical characteristics of dark brown or

tanner's cod oil 224

Detection of adulteration of cod oil with mineral oils, brown seal and menhaden oils; Use of Bank and Straits oils as substitutes for cod oil. 225

XVI CONTENTS.

PAGE

Degras; English sod oil 226

French moellon oil; Tallow; Oleo-stearine ; Paraffine wax ; Principal stuffing used for upper leather ........ 227

The "Ideal" grease; Neatsfoot oil ; Menhaden, Straits or Bank oil; Menhaden fisheries; Preparation of the oil ....... . 228

Porpoise oil; Tunny oil; Neatsfoot oil . 229

Degras; Manufacture of degras in France; Mixture of degras and fish oil 230

Vickers' degras; Early use of sod oil or French degras; Former manufacture of sod oil; Injurious effect of the sulphuric acid used in making sod oil; Method of getting rid of an excess of acid in sod oil. . 231

Method used in France for tanning oil-dressed leather and for making sod oil; American process of oil dressing ...... 232

European method of oil dressing 233

The most valuable and characteristic property of genuine sod oil; The tanning principle of pure sod oil ; Amount of tanning principle in menhaden, Bank and Straits' oils, and in genuine cod oil . . 234

On what the value of fish or cod oil as a leather lubricant depends; Paraffine wax . . . . : 235

Glycerine; Changes created by the introduction of mineral salts in the manufacture of leather 236

Production of glycerine; Properties of glycerine; Use of glycerine for

oiling in the place of fat or degras 237

Necessity of mixing glycerine with supplementary ingredients; Methods for effecting a better adherence of the glycerine to the leather . . 238

Combination of glycerine with tannin; Practical method of stuffing with glycerine 239

Testing oils; Simple tests for determining the amount of compounding 240

Evil effects of the bad conditions of fats; Mode of distinguishing a genuine degras from simple fat emulsions ; Most usual adulteration of degras 241

Borax; steam jacket kettles; Stuffing or fat liquoring with Palermo fig

soap 242

Formula for making fat liquors with Palermo fig soap; Fat liquors . 243

Chromol fat liquors for chrome tanned leather, directions for use; Water-proof stuffing 244

Water-proofing leather; The mineral process; Stuffing compounds; Paraffine wax for giving leather the quality of water-resisting . . . 245 Formulae for producing water-proof leather 246

CHAPTER XVI. Setting-out

Considerable amount of labor required in setting heavy leathers; Stoning-out, scouring and setting-out machine built by the Vaughn Machine Co. _ 248

CONTENTS. XV11

CHAPTER XVII. Whitening and Shaving Leather

PAGE

Various ways of whitening; French pattern of whitening slicker; Form

of beam generally employed in currying shops ..... 250 Union whitening and buffing machine made by J. T. Freeman & Co. 251 Shaving machine; The Rood improved shaving machine, manufactured by the Vaughn Machine Co 254

CHAPTER XVIII. Bracking Leather

Forms of blacking brushes in common use 256

Leather blacking, coloring and dressing machine patented by Batchelder, and built by the Vaughn Machine Co. ..... 257

Chapter XIX

Machines for Rolling, Pebbung, Glassing or Polishing, Finishing, etc.

The glazing machine one of the first steam-driven tools introduced into the trade; The Bowers rocker-motion leather finishing machine. . 263

Improved iron glassing jack made by J. T. Freeman & Co.; Improved straight bed rolling or pebbling jack made by J. T. Freeman & Co. 266

Martin's improved machine 267

The Knox improved inclined bed leather finishing and pebbling machine 268

The Coombs pendulum jack, made by the Vaughn Machine Co. . . 271

CHAPTER XX. Staking Machines

"Hand method" staking machine built by F. F. Slocomb & Co. . 273

Staking machine built by the Vaughn Machine Co 274

Staking machine built by Wm. F. Martin, Salem, Mass. . . . 275

XV111 CONTENTS.

CHAPTER XXI. Machine for Measuring Leather

PAGE

Modes of selling leather; Sawyer's leather measuring machine . , 277

The Union leather measuring machine 279

The Bolton machine 281

CHAPTER XXII. Mineral Tanning Substances — "Chrome," or Mineral Tannage

Characteristics oe Chrome-Tanned Leather —

Currying — Dyeing.

Principal mineral substances; Aluminium sulphate; Preparation of neutral aluminium sulphate; Properties of aluminium sulphate . . 282

To make aluminium sulphate containing free sulphuric acid available for tanning purposes; Alum, its formation and properties . . . 283

Splitting up of the alum in absorption by the skin tissue; Aluminium acetate and its properties; Advantages claimed for aluminium acetate. 284

Chromium salts; Potassium bichromate, its manufacture and properties. 285

Sodium bichromate; Calcium bichromate, strontium and barium and the neutral chromates of calcium, strontium and barium; Chromium alum; Chromic sulphate ......... 286

Hyposulphite of soda; Ferric salts; Recommendation in the last century of tanning with ferric salts by D'Arcet; Bordier's patent; Attempted reintroduction by Knapp of tanning with ferric salts .... 287

Preparation of an iron soap; Common salt and its importance in tanning; Varieties and preparation of common salt 288

" Chrome " or mineral tannage; The first use of bichromates for tanning made by Cavalin, and his method; Impossibility of a practical application of this process ......... 289

Knapp's patent for tanning with ferric salts and other metallic oxides; Patent for the preparation of a basic ferric sulphate and its use for tanning obtained by Pfanhauser; Knapp's new method of tanning with ferric salts . . . . . . . . . 290

New and peculiar features claimed for this purpose by Knapp . . 291

Nature of the leather prepared by Knapp's process; Additional patent applied for by Knapp for a somewhat different method of preparing ferric salt. 292

Heinzerling's patented process for quick tanning with chromates and its execution ............ 293

CONTENTS. XIX

PAGE

Directions for working the upper aud sole leather obtained by this process into shoes 295

Advantages of chrome leather; Abandonment of the above mentioned methods of tanning on account of the defective quality of the product produced by them; Requisite characteristics of the mineral tanning substance. 296

Usefulness of the salts of aluminium, iron and chromium ; The two methods of chrome tanning now in practical use; The two-bath process and the one-bath process; The Schultz patents and the Dennis patent; Treatment in the Schultz method 297

Commercial leather of superior quality by the Schultz process first made by Robert H. Foederer, of Philadelphia, Pa., and Wm. Zahn, of Newark, N. J.; Simplification of the art of chrome tanning by the Dennis "one-bath " process 298

Tanolin and its advantages 299

Varieties of leather tanned by the Dennis process; Necessity of circumspection when embarking in the new field of chrome tannage . . 300

High standing of American morocco and kid manufacturers; Abandonment of the old currier style of shaving on the wooden beam face; Rapid increase in chrome tannage; Properties of chrome npper . . 301

Competition of chrome tanning with bark; Impetus to the demand for sporting shoes ............ 302

Tanning calf or goat skins by the chrome process ; Directions by the Martin Dennis Chrome Tannage Co. for using tanolin on calf or goat skins. . . 304

Tanning sheep skins by the chrome process; Some patents for chrome tannage 306

Information regarding the Dennis "one bath " process of chrome tannage; Application by the German tanners of chrome tanning to the production of a great variety of leathers ...... 307

The Dennis tanning liquor; Specification of the patent .... 308

The Dennis process of tanning leather; Specification of the patent . 313

Characteristics of chrome leather ........ 319

Currying chrome leather; Preparation and use of "fat liquors " . . 321

To prepare chrome-tanned leather for dyeing; Patent granted to E. Avellis and Emil Koester of Berlin, Germany; Practical example of the process 322

Dyeing chrome leather; Dyeing with neutral basic aniline colors; Dyeing with acid aniline colors; Fixing alizarine colors; The best " all-round " mordant to be used on leather 323

Dyeing leather with alizarine colors ; H. Koechlin and E. Knecht's method 324

XX CONTENTS.

CHAPTER XXIII. Kid or Morocco Leathers

PAGE

Great revolution in morocco manufacturing in ten years by the introduction of the new agent, chrome; Patents issued to Augustus Schultz

of New York City 326

Reasons given by Mr. Schultz for taking out two patents; Assignment

and transfer of Schultz's patents to various parties .... 327 William M. Norris on the advantages of chrome tanning . . . 328

Preparing the skins 330

Lime vats in a kid morocco factory; Breaking, fleshing, unhairing,

and slating machine 331

Washing the skins 334

Influence of the previous treatment of the raw pelt on the leather produced by any one of the chrome processes; Liming and deliming;

Slating 335

The bran drench; Tawing according to the Schultz patent; Preparation of the baths; Test for the completion of tanning .... 336