Front matter
LOUIS. E. ANDES
THE TREATMENT OF PAPER FOR SPECIAL PURPOSES
I
Preface
Of all the materials now in extensive use, paper is probably the one attracting the greatest attention, by reason of its manifold application to the production of useful articles. Thin sheets of paper are now made up, not merely into articles that retain the characteristics of the material, in some cases coated or coloured, but also into others in which the original material has disappeared, homogeneous solid substances being formed that are capable of competing with wood or iron in point of durability and elasticity. Instructions for working paper up into a great variety of articles are to be found in a large number of books and periodicals; and the author has under¬ taken the task of collecting and sifting them, in the hope that the result will prove beneficial to all trades in which paper is used as a raw material.
LOUIS EDGAR AND&3.
Chapter I
Parchment Paper, Vegetable Parchment Making Parchment Paper The Parchment Paper Machine .
Opaque, Supple Parchment Paper Thick Parchment ....
Kugler’s Parchment Paper and Parchment Slates Double and Triple Osmotic Parchment .
Anti-Erasion Paper and Parchment
Staining Parchment Paper
Utilising Waste Parchment Paper
Parchmenting Linen, Woollen, and Cotton Fabrics
Parchment Millboard ....
Wood’s Artificial Parchment
Imitation Horn and Ivory from Parchment Paper
Pergamyu (Grease-Proof Imitation Parchment Paper)
Impermeable Parchment Paper .
Parchmented Millboard ....
Parchment Paper Filters.
Elastic Mass from Vegetable Parchment.
Imitation Parchment Paper
Artificial Parchment ....
Testing the Sulphuric Acid
28 29
31 31
32 32 34
CHAPTER II. Pater for Transfer Pictures (Metachromotypes) . . 39
Transfer Papers for Decorating Glass . . . .42
Transfer Papers for Glass Etching . . . .43
vii viii
Chapter III. Page
Butter Paper . . . . . . .44
Needle Paper . . . . . . .45
Salicylic Paper . . . . . . .45
Paraffin Paper . . . . . . .47
Wrapping Paper for Silverware . . . . .48
Waterproof Paper . . . . . .48
Hygroscopic Paper . . . . . .48
Anticorrosive Paper . . . . . .49
CHAPTER IV. Antony’s Method . . . • . .51
Grossheim’s Method . . . . . .51
Tischler’s Method . . . . . .54
CHAPTER V. Fireproof and Antifalsification Papers . . .56
Fireproof Papers ....... 56
Antifalsification Paper . . . . . .59
Calomel Paper for Preventing Falsification of Documents . 59
Antifalsification Paper . . . . . .60
CHAPTER VI. Vulcanised Papier Mach4 . . . . .62
Paper Bottles . . . . . . .64
Unbreakable Writing Tablets . . . . .65
Plastic Articles of Paper . . . . . .66
Waterproof Coverings for Walls and Ceilings . . .67
Parchment Slates . . . . ... 68
Flanges and Manhole Rings . . . . .68
Paper Wheels, Roofing, and Boats . . . .69
Paper Barrels . . . . . . .70
Paper Gaspipes . . . . . . .72
Paper Boxes . . . . . . .72
Paper Horseshoes . . . . . .72
IX
Chapter VII. Page
Machine for Gumming Paper . . . . .78
CHAPTER VIII. Hectograph Papers . . . . . .80
Hectograph Sheets . . . . . .80
Endless Hectograph Paper . . . . .81
CHAPTER IX. Fly Papers ....... 83
(a) Saccharin Paper . . . . . .83
( b ) Non-poisonous Colocynth Paper. . . .83
(c) Non-poisonous Quassia Paper . . . .84
(d) Non-poisonous Vegetable Fly Paper . . .84
(e) Poisonous Fly Paper . . . . .84
Non-poisonous Papers for destroying Rats and Mice . . 85
Moth Papers . . . . . . .85
CHAPTER X. Chalk and Leather Papers . . . . .88
Glac6 Chalk Paper . . . . . .88
Warren de la Rue’s Paper . . . . .88
Chalk Paper : Papier M6tallique, Ivory Paper . . .89
Leather Paper . . . . . . .89
Kellog’s Leather Paper . . . . .89
Leather Paper . . . . . .90
Klein’s Imitation Leather . . . .91
CHAPTER XI. Luminous Papers — Blue-Print Papers — Blotting Papers . 93
Luminous Paper . . . . . . .95
Blue-Print and Similar Papers . . . . .96
Albumin Blue-Print Papers. . . . .96
Haupt’s Sensitive Paper . . . . .96
Ferro-Prussiate Blue-Print Paper . . .97
(a) For Blue Lines on a White Ground. . . 97
( b ) For White Lines on a Blue Ground. . . 97
X
PAGE
Indigo Blue-Print Paper . . . . .98
Heliographic Paper (Black Lines on a White Ground) . 99
Photographic Transfer Paper . . . .99
Blotting Papers ....... 100
Ink Eradicator Paper . . . .100
Blotting Paper . . . . . .100
Paper Stencil Plates . . . . . .100
CHAPTER XII. Metal Papers and Medicated Papers .... 105
Brandt and Nawrocki’s Method ..... 106
Molten Metallic Paper ...... 107
Medicated Papers . . . . . .108
Aseptic and Antiseptic Papers . . . .108
Varnished Paper . . . . . .109
Gout Papers. ...... 109
Yellow Gout Paper ..... 109
Brown Gout Paper . . . .109
Christy’s Chrome-Gelatine Bandaging . . . 110
Ricou’s Anti- Asthma Paper. .... 110
Papier China ique ...... 110
Blister Paper (Papier Epispastique) .... 110
Winsly Paper (Papier Winsly) . . . .111
East Indian Paper Plaster for Slight Flesh Wounds . Ill
Mustard Paper . . . . . .111
Hygienic Paper Handkerchiefs .... 112
Millboard Splints ...... 112
Iodine Paper . . . . • .113
Gautier’s Nascent Iodine Paper .... 113
CHAPTER XIII. Marbled Parer ....... 117
Apparatus for Marbling Paper ..... 119
Paper Sprinkling Machines . . . . .132
CHAPTER XIV. Recipes for Oil or Varnish Tracing Paper . . . 137
Waxed Tracing Paper ...... 139
XI
PAGE
Temporarily Transparent Tracing Paper. . . .139
Victoria Tracing Paper . . . . . .140
Coloured Copying Papers (Carbon Papers) . . .140
Graphite Paper (Black Carbon Paper) .... 141
Double-coated Carbon Papers for Copying from the Negative Inscription ....... 141
Backing for Sheets of Copying Paper .... 143
Ferruginous Copying Paper ..... 143
Iridescent or Mother-of-Pearl Papers .... 144
Beinisch’s Iridescent Paper ..... 144
Puscher’s Iridescent Paper for Visiting Cards, etc. . . 144
Imitation Mother-of-Pearl ..... 145
Mother-of-Pearl Paper ..... 145
CHAPTER XV. Albuminised Paper . . . . . .147
Bromide Albumin Paper for Enlargements . . . 149
Bromide Paper . . . . . . .149
Zitterow’s Collodion Photographic Paper . . .149
Ferro-Gum Paper ...... 150
Gelatine Paper for Photo-Zinco Work .... 150
Matt Albuminised Paper . . . . .151
Stable Sensitised Paper . . . . . .152
Heliochrome Paper . . . . . . 153
Sensitised Paper for Photo-Zincography .... 154
Instantaneous Positive Paper . . . . .156
Halleur’s Photographic Paper . . . . .156
Photo-Lithographic Paper . . . . .156
Pigmented Photographic Paper ..... 157
Platinum Paper . . . . . . .160
Shellac Paper . . . . . . .162
Fumigating Papers . ...... 162
Combustible . . . . . . .163
Incombustible ....... 163
Other Recipes ....... 163
Armenian Paper ....... 164
Litmus Paper . . . . . . .164
Blue Litmus Paper . . . . . .165
Red Litmus Paper ...... 165 xii
PAGE
Turmeric Paper ....... 166
Tetramethyl-Paraphenyl-Diamine Papier . . . 166
Different Test Papers . . . . . .166
Oenocrine Paper . . . . . . .167
CHAPTER XYI.
Papers for Cleaning and Polishing Purposes . . 168
Glass Paper . . . . . . .169
Pumice Paper . . . . . . .174
Emery Papier . . . . . . .176
Paper Substitute for Cotton Waste .... 188
CHAPTER XVII. Lithographic Transfer Papers ..... 190
Scotch Transfer Paper . . . . . .191
Un stretchable Transfer Paper ..... 191
Unstretchable Sensitive Transfer Paper .... 192
Transfer Paper . . . . . . .192
Tracing and Transfer Papier . . . . .193
Autographic Paper . . . . . .193
CHAPTER XVIII. Satin Paper ....... 195
Ivory Paper for Miniatures . . . . .195
Enamel Paper ....... 196
Metallic Paper (Papiier M6tallique) .... 197
Telegraphic Paper . . . . . .197
Paper for Gun Cartridges . . . . .197
Tortoiseshell Paper . . . . . .198
Artificial Snow Paper . . . . . 198
Weather-Gauge Papers ...... 200
Toughened Filter Paper ...... 200
Paper for Magic Lantern Pictures .... 201
Split Paper . . . . . . .201
Contents xiii
page
Charred-Outline Pictures ..... 203
Flexible Mirrors ....... 203
Sulphur Paper ....... 203
Artificial Flower Paper ...... 204
Indelible Pictures ...... 204
Barometer Pictures (Weather-Gauge Pictures) . . . 205
Albumin Clarifying Paper ..... 205
Insulating Paper ....... 206
Electric Paper ....... 206
Paper Floor Covering ...... 206
Paper Matches . . . . . . .207
Crocodile Tears — Physical Toy ..... 207
Magic Pictures ....... 208
Laundry Blue Papers ...... 209
Blue Paper for Bleachers’ Use ..... 211
CHAPTER XIX. Washable Drawing Paper . . . . .212
Waterproof Satin Paper ...... 212
Impervious Paper ...... 213
Impervious Packing Paper for Hygroscopic Substances . . 213
Waterproofing Composition for Cellulose Casks . . .213
Waterproofing Composition for Cartridges . . .214
Washable Card for Photographic and Lithographic Purposes . 214
Anti- Perspiration Socks ...... 215
Washable Coloured Paper ..... 215
Waterproof Paper ...... 218
Blackburn’s Recipe . . . . . .218
Mitschele’s Recipe . . . . .218
Carmichael’s Recipe . . . . . .219
Dorian’s Recipe . . . . . .219
Bird’s Recipe . . . . . .219
Waterproof Millboard . . . • . 220
Sugar Paper ....... 220
CHAPTER XX. The Characteristics of Paper — Paper Testing . . 222
THE TREATMENT OF PAPER FOR SPECIAL PURPOSES
CHAPTER I. Parchment Paper, Vegetable Parchment
ARCHMENT paper is the name given to paper that has undergone such modification by treatment with sulphuric acid that it no longer softens or separates into its constituent fibres on being immersed, or even boiled, in water, but retains its coherence, is impervious to water and air, and preserves its newly acquired properties when re-dried. The parchmenting process by which this change is effected is based on the power of sulphuric acid to convert the superficial strata of pure cellulose into a gelatinous mass, which forms a pro¬ tective coating for the rest. This gelatinous mass is a substance, amyloid, similar to starch, and when subjected to the continued action of sulphuric acid undergoes further conversion into a gummy substance, wood dextrin. Amyloid therefore appears to be that conversion-product which unites the fibres so firmly and intimately as to conveit them into a coherent mass which has entirely lost the property of solubility in water, and at the same time has considerably modified the longitudinal and transverse extensibility of the fibres, whereby i
2 Treatment oe Paper for Special Purposes their strength is greatly increased. If a strip of unsized paper be dipped in sulphuric acid the fibres swell up and become coated with the aforesaid gelatinous envelope, which extends throughout the entire mass if the exposure to the acid be sufficiently prolonged. According to Hoffmann, amyloid is still imperfectly known, being regarded by some chemists as a kind of cellulose, and by others as an intermediate stage between starch and cellulose. Any one desiring to prepare amyloid as a matter of scientific interest can do so by treating 1 part of pure cotton with 30 parts of dilute sulphuric acid (4 parts of acid to 1 of water). The cotton speedily dissolves, and at the end of about half a minute forms a stiff gelatinous mass, which gradually becomes more fluid, so that in 15 minutes it attains the consistency of syrup. On treating this with water, amyloid separates out as a white, flocculent, gelatinous substance in which no fibrous structure can be detected. If the acid mass be left alone for some time longer, it gradually changes into dextrin and sugar ; and if the addition of water be delayed until 7-8 hours have elapsed, only a very small quantity of flocculent matter will be pre¬ cipitated. In presence of acids and alkalis, amyloid behaves just the same as vegetable fibres, differing from these merely in its lack of structure, and from starch inasmuch as the blue coloration imparted by iodine can be removed by washing with water.
When mixed with a sufficiency of water, amyloid has a glutinous appearance, and if spread out on a sheet of glass will dry to a thin, tough, transparent film. If dried on paper it does not adhere to the latter, but can be readily detached, though when deposited direct on paper from its solutions, as is done in the preparation of vegetable parchment, it remains unalterably combined with the fibres. Under the microscope the fibres of vegetable parchment can be plainly seen to be enveloped in a thin, transparent skin, and it is perfectly certain that, through the action of the acid, the fibres have received a coating of amyloid, from the fact that the superficial layer is stained blue by iodine, whilst the interior retains its shape unaltered, even in the case of the finest flax fibres. Unsized paper dipped in dilute sulphuric acid at ordinary temperature immediately becomes coated with a gelatinous film, and in the same way the surface of the individual fibres will suffer alteration if time be given for the acid to penetrate. On removing the paper from the acid bath and dipping it in water containing ammonia or caustic soda, the influence of the acid is stopped, and the acid mass separates into amyloid, which unites the fibres to a dense mass, and sulphuric acid which is eliminated by washing. The gelatinous film covering the surface of the paper facilitates the setting of the fibres together in drying, by permitting the escape of the water vapour expelled from the interior, but retarding the penetration of the air by which the water would otherwise be replaced. This behaviour explains the dried, transparent appearance of many kinds of such parchment.
Filter paper that has been washed with hydrochloric acid and hydrofluoric acid may be regarded as almost perfectly pure cellulose. If this, when dried, be impregnated with 50 per cent, sulphuric acid it furnishes a transparent, gelatinous mass, which will retain its appearance unchanged for any length of time. At 100° C., or even below that temperature conversion into dextrin occurs very rapidly. When thoroughly washed this colloidal cellulose, for so the mass may be termed will dissolve in pure water. The removal of the final traces of acid is facilitated by washing with ordinary alcohol, and drying at a gentle heat. When the mass is taken up’ with water it forms a rather milky fluid, which filters readily, and thereafter will not deposit any sediment, even during several days, but readily undergoes alteration on boiling. By the aid of a new Laurent compensator, it was ascertained that a 4-inch stratum of the solution of colloidal cellulose deviates the plane of polarisation f° to the right. In contrast to the achroo-dextrins this colloidal cellulose is thrown down from solution by very small quantities of extraneous sub¬ stances : sulphuric acid, nitric acid, common salt, sodium sulphate, etc., as well as by a sufficiency of alcohol. When dried on marble coated with vaseline, the colloidal cellulose gives a lustrous, semi-transparent film, which dissolves com¬ pletely in cold water. A very short immersion in sulphuric acid of G93 B. density (or a little longer if the density be 55°), renders the colloidal cellulose insoluble in that acid, a small quantity of dextrin being formed at the same time. The substance may also be nitrated under the same conditions as ordinary cellulose. The properties of colloidal cellulose afford an explanation of many circumstances noticed in making parchment. Certain very thin vegetable parchments will cede colloidal cellulose to boiling water, which is not the case with the thicker kinds, owing undoubtedly to the fact that a stronger acid is used in making the latter, the colloidal cellulose, which is also formed in this case, becoming insoluble. To some extent vegetable parchment forms a tissue of ordinary cellulose, the pores of which are filled with colloidal cellulose. That this is so can be demonstrated by applying colloidal cellulose to ordinary filter paper on both sides, allowing it to dry slowly, and then passing it through a calendering machine between two sheets of polished zinc. The resulting product exactly resembles vegetable parchment that has been satinised in the same way. Colloidal cellulose differs from any natural product that has hitherto been examined.
The alterations sustained by vegetable parchment, in com¬ parison with the paper from which it is made are somewhat extensive. For instance, the strength is increased three- or four-fold, whilst at the same time the sp. gr. increases by 32-42 per cent., and the thickness shrinks 34-37 per cent., a certain proof that the individual particles of the paper move closer together during the process. This increases the homo¬ geneity and transparency, and consequently the resemblance to animal membrane and true parchment, a circumstance to which the product owes its distinctive name.
It is an essential preliminary to the production of parchment paper that the paper forming the raw material should be perfectly free from any substances capable of retarding the process or jeopardising the formation of a uniform product. For this reason the paper used must neither be sized nor contain any mineral substances whatsoever. Long staple paper, made from rags, is the best material, though wood pulp and straw pulp are not precluded. Sulphuric acid is generally used as the parchmenting reagent, though solutions of ammoniacal copper oxide or zinc chloride are employed as being capable of effecting the same transformation.
To ensure success it is necessary that the parchmenting solution should be of a certain concentration, and used at a certain temperature ; and it may be conveniently mentioned here that these conditions are fulfilled by the use of 9-9.', parts of English concentrated sulphuric acid, or the undiluted chamber acid (60 J B.), at a temperature not exceeding 10’ C. The acid-free zinc chloride solution, obtained by dis¬ solving zinc in hydrochloric acid, should he concentrated to the consistency of syrup, and employed at a temperature which may range from 50-100° C. according to the actual con¬ centration.
The time allowed for the action of the parchmenting reagent is an important factor, and depends — apart from the nature of the liquid — on the thickness and composition (material) of the paper; pure, thin paper for instance requiring only 3-5 seconds, whilst thicker paper will take longer (up to 12 seconds). The action of the acid must be stopped immediately the proper exposure lias been given, by a thorough washing, supplemented by neutralisation with alkaline lyes, or the like, the paper being dried after a final washing with pure water. The necessary precautions to adopt in order to prevent the paper from wrinkling will be referred to later on.
To obtain a dense, strong parchment, care must be taken to see that the alteration is confined to the surface of the fibres, and that the paper employed is not porous, as this would furnish a weak, though dense product. A thin, firmly twisted cotton thread, for example, will receive a greater accession of strength by treatment with sulphuric acid, than a loosely twisted one of twice the thickness. Thin, dense cotton material, the fibres of which have been forced closely together by pressing before putting them through the acid treatment, will yield an article of such strength that in many cases it can be used as a substitute for leather, and when made supple by greasing is capable of numerous applications.
At the present time paper in sheets is rarely used for making parchment paper on a manufacturing scale ; and the operation of dipping the paper in the acid bath is almost invariably performed by machinery. A sufficient length of unsized paper, mounted on rollers, is introduced into a lead or glass tank, and is passed round a lead or glass roller, through the acid bath. Before leaving the tank the dipped paper traverses a pair of squeezing rollers, to express the surplus liquid, and is afterwards led through a series of washing tanks supplied with a constant flow of fresh water. To eliminate the last traces of acid, the paper is finally passed through a washing tank, the water in which receives an addition of alkali at intervals, and the operation is completed by rinsing in pure water. The more effective the washing before the paper reaches the neutralising tank, the smaller the con¬ sumption of ammonia ; and it is therefore to the interest of the manufacturer to wash the paper so completely as to render the use of ammonia a supplementary, rather than a necessary, precaution. After the final rinsing the paper is passed through a pair of felt rollers, to remove as much of the water as possible, ancl is then stretched between layers of dry felt on a drying cylinder, from which it is removed before it becomes quite dry, and is smoothed between rollers heated by steam. During the drying process it is essential that the parchment paper should be kept well stretched transversely, since it shrinks much more than ordinary paper, and would otherwise become uneven. Very thick parchment paper is made by passing two separate layers of paper through the acid bath, then uniting them in front of the first pair of rollers before entering the washing tanks, and passing them together through the pressure rollers. In this way the two layers will adhere so firmly together that they cannot afterwards be separated.
The peculiar properties of parchment paper render it suitable for numerous applications, such as legal and other documents, insurance certificates, banknotes, drafts, important records, and in fact all documents whose preservation is a matter of importance. One method sometimes adopted for preserving these documents against fire is to pack them in strong boxes, which are then allowed to become encrusted with crystals of alum or some other salt. In the event of fire, the water of crystallisation is converted into steam, which protects the parchment paper documents more effectually from destruction than if ordinary paper had been used. Parchment paper is also far better able to withstand insect ravages than ordinary paper; and this power may be still further increased by incorporating certain compounds (mercury salts, for example) with the paper before it is treated with acid. It can also be recommended for making banknotes, since the lettering on paper that has been parchmented after printing can no longer be scratched out without entirely destroying the substance of the paper itself. Another advantage of parchment paper is, that writing on such paper is very difficult to remove and replace by fresh text, so that a considerable degree of security
8 Treatment of Parer for Special Purposes is afforded against falsification. Owing to its strength and durability, parchment paper is adapted for plans, especially those made for building purposes and exposed to wet weather and careless handling. The thin, transparent sheets make very good tracing paper. Parchment paper can also be largely used for binding books, being durable and of excellent appearance. This latter quality also characterises books, cards, etc., made of the same material, the paper being printed after being parchmented, since it shrinks under the acid treatment. Parchment paper readily absorbs printer’s ink, as well as ordinary writing ink, and it will fix dyestuffs in general more readily than calico does, for instance. There is no need to expatiate on its usefulness for covering glasses and other vessels containing substances liable to deterioration, such as preserves, extracts, etc., for wrapping fatty products or the like, for capsuling corked bottles, and so forth. Furthermore, it serves for wrapping tobacco and other substances, to prevent the escape of contained moisture or the absorption of moisture from the air. Still further applications are for luting the joints of stills and other apparatus, making small bags, the edges of which are cemented with gelatine, for cooking and steaming food, etc.
The properties of parchment paper are detailed by Kletzinsky as follows :
“Vegetable parchment is unaffected by caustic potash, and will also resist the action of cold acid better than animal membrane. Experiments have shown that parchment paper forms just as good a covering for receptacles as the best animal bladder. Hot, concentrated hydrochloric acid will dissolve phyto parchment to glucose, apart from a small fibrous residue."
When vegetable parchment is soaked in water, which is then heated to boiling and treated with sulphuric acid, a somewhat violent reaction ensues, and if the resulting dark brown acid pulp be at once diluted with water, a slightly coloured solution of sugar is obtained that can be freed from sulphuric acid by adding milk of lime. The precipitated gypsum carries down with it the undecomposed particles of paper, and clarifies the liquid, which can then be treated for tbe production of alcohol. If the manufacture of parchment paper should ever attain the degree of importance it deserves, the waste products will easily find a more suitable application than conversion into spirit.
Given careful preparation and sufficient washing, no increase occurs in the weight of the paper, the amount of sulphuric acid retained being imponderable ; and consequently the remark¬ able and technically valuable alteration sustained by the paper in the acid treatment is purely molecular. Equally surprising are the shrinkage and contraction set up in the process. The paper becomes slightly thicker, but its super¬ ficial area diminishes by 10-30 per cent, according as the exposure to the acid bath ranges between 10 and 15 seconds ; this shrinkage being in no way compensated by the slight increase in thickness, the augmented strength is at once explained on a physical basis.
With regard to the use of parchment paper for closing glasses containing alcoholic liquids, the following statement is made: A wide sugar-glass was filled half full of strong spirit, and then tied up with moistened parchment paper. When dried, it set as firm and hard as pig’s bladder. After the vessel had stood in a warm place for three weeks, only a very small quantity of the alcohol had evaporated : in fact, the strength of the spirit had increased to a small extent (about \ a degree). This is not difficult to understand when it is remembered that both paper and bladder are more permeable to water vapour than to that of spirit.
The behaviour of parchment toward white or fuming nitric acid, of sp. gr. 1 *4—1 '6, is important. If a sulphuric parchment be dipped in such acid for 10 minutes at least, and then washed thoroughly with water, it will be found to have increased 10-20 per cent, in thickness, and to a considerable degree in strength, the shrinkage of superficial area being much smaller. When washed and dried under moderate pressure it exhibits a perfect resemblance to parchment, with greatly increased powers of resistance to mechanical abrasion and atmospheric influences. When dried and re-dipped in dilute sulphuric acid this nitro-parchment becomes glass-clear and transparent, besides being more resistant to acids. On the other hand, it dissolves to a golden yellow solution in boiling caustic potash, and like all other nitro-compounds it burns readily like touch-paper.
Experiments have been made to determine the comparative strength of parchment paper, ordinary paper, and animal parchment. With this object, test strips of parchment paper and parchment were cut to a length of 22‘2 mm., the ends being then clamped to horizontal cylinders, so as to form a loop of the material in each case. Through each loop was passed a small wooden cylinder, fitted at the ends with small cords supporting a pan for the reception of weights, and the pans were weighted until the test strips broke. A series of these trials showed that parchment paper has about five times the strength of the paper from which it is made, and that parchment paper is about three-fourths as strong as ordinary parchment of equal thickness. It was also found that the strips of parchment paper are very unequal in thickness, con¬ siderable differences in this respect being observable even in strips cut from one and the same piece.
Although parchment paper may be inferior to the real article in point of strength, it is far superior in its power of resisting the influence of chemical reagents, water in particular, for whilst it absorbs an equal quantity of that liquid and becomes perfectly soft and flexible, it can be left in contact therewith for several days, and even boiled, without suffering in the least.
Parchment Paper, Vegetable Parchment i i
When dried again it regains its original appearance and' strength. Ordinary animal parchment on the other hand is soon attacked by boiling water, and is gradually changed into gelatine. Even at the ordinary temperature it is very prone to putrefy in presence of moisture, whereas the n on-nitrogenous vegetable parchment can be exposed to moisture without suffer¬ ing the slightest alteration.
From experiments made by A. Sudicke with parchment paper from the Helfenberg Works, near Dresden, it appears that paper in the course of transformation into vegetable parchment increases in thickness by about 34-44 per cent., and by 32-42 per cent, in specific gravity. The strength of the crude paper Avas 2f-3 lb. per sq. yd., and that of the finished parchment paper 10|-12| lb.
For many purposes it is necessary that parchment paper should be sized ; and tubes of this paper intended to replace sausage skins, require to be fastened with some adhesive, the provision of which was found somewhat difficult at first, until Jacobsen succeeded in devising a suitable preparation. The reliability of this preparation was tested in a large sausage factory in Berlin, some two million tubes being tried.
When several sheets of parchment paper are gummed to¬ gether, they form an extremely strong material, greatly resembling real parchment, and valuable to the bookbinder. Again, parchment paper gummed on to packing cloth makes a waterproof wrapping that should find extensive application.
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You’ve reached the end of The treatment of paper for special purposes : a practical introduction to the preparation of paper products for a great variety of purposes such as parchment paper, transfer papers, preservative papers, grained transfer papers, fireproof and antifalsification papers, polishing papers, tracing and copying papers, chalk and litho transfer papers, leather papers, luminous papers, tortoiseshell and ivory papers, metal papers, coloured papers, etc. etc., and paper articles.