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 DEPARTMENT OF COMMERCE 
 
 Technologic Papers 
 
 OF THE 
 
 Bureau of Standards 
 
 S. W. STRATTON, Director 
 
 No. 160 
 
 EFFECTS OF OILS, GREASES, AND DEGREE OF 
 
 TANNAGE ON THE PHYSICAL PROPERTIES 
 
 OF RUSSET HARNESS LEATHER 
 
 BY 
 
 R. C. BOWKER, Assistant Mechanical Engineer 
 
 Bureau of Standards 
 
 in cooperation with 
 
 J. B. CHURCHILL, Director 
 
 American Leather Research Laboratory 
 
 Aprii 17,1920 
 
 %L ^*7 
 
 PRICE, S CENTS 
 
 Sold only by the Superintendent of Documents, Government Printing Office 
 Washington, D. C. 
 
 WASHINGTON 
 
 GOVERNMENT PRINTING OFFICE 
 
 1920 
 
 Monograph 
 
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EFFECTS OF OILS, GREASES, AND DEGREE OF TAN- 
 NAGE ON THE PHYSICAL PROPERTIES OF RUSSET 
 HARNESS LEATHER 
 
 By R. C. Bowker and J. B. Churchill 
 
 CONTENTS 
 
 Page 
 
 I. Introduction 3 
 
 II. Methods 4 
 
 1. Selection of the leather 4 
 
 (a) Description of the leather selected 4 
 
 (6) Preparation of samples 6 
 
 2. Physical tests 7 
 
 (a) Tensile strength 7 
 
 (£) Stretch 7 
 
 (c) Buckle strength 8 
 
 3. Chemical tests 8 
 
 (a) Stuffing content 8 
 
 (b) Complete analysis 8 
 
 III. Data and results obtained 9 
 
 1 . Physical tests 9 
 
 (a) Tensile strength 9 
 
 (6) Stretch 12 
 
 (c) Buckle strength 13 
 
 2. Chemical tests 14 
 
 (a) Stuffing content 14 
 
 (b) Complete analysis 15 
 
 3. Comparison of physical and chemical tests 16 
 
 (a) Effect of the amount of stuffing content on the physical 
 
 properties 16 
 
 (b) Effect of the degree of tannage on the physical properties. . 17 
 
 (c) Effect of animal and mineral oils on the physical properties- 18 
 
 IV. Conclusions 18 
 
 I. INTRODUCTION 
 
 During the war physical and chemical tests of the equipment 
 leather purchased by the War Department were made at the 
 Bureau for the purpose of controlling the quality of the leather 
 furnished by the various tanneries. An opportunity was thus 
 offered for a study of the variations in the physical properties 
 and in the chemical constituents of many kinds of leather. On 
 account of the large quantities used the values of the various 
 
 3 
 
4 Technologic Papers of the Bureau of Standards 
 
 properties for both russet and black harness leathers were of special 
 interest. Russet harness leather is not a regular commercial 
 product in this country and finds little use except for military 
 purposes. Black harness leather, however, is a regular commer- 
 cial product and is widely used. Besides the difference in color, 
 there are three distinct differences between these two leathers 
 caused by the process of manufacture. The first of these differ- 
 ences occurs in the length of the tanning operation. It is general 
 practice to give hides for black harness leather a short-time 
 tannage, while those for russet harness leather are tanned for a 
 longer time. The average degree of tannage as determined from 
 the chemical analyses of black and russet harness leathers made 
 during the war were 46 and 61, respectively. The second point 
 of difference between these two kinds of leather is shown by the 
 amount of stuffing used. The average amounts found in the 
 above-mentioned black and russet leathers were 29.3 and 15.5, 
 respectively. The third difference is caused by the general prac- 
 tice of adding to black harness leather small amounts of such filling 
 materials as glucose and salts. This procedure is not generally 
 followed in the case of russet harness leather. A better selection 
 of hides is generally used for the latter leather, since the coloring 
 of black harness readily conceals many surface imperfections 
 which do not affect the quality. In order to study more definitely 
 the effects of the amount and kind of stuffing content and also the 
 degree of tannage on the physical properties of harness leather, 
 this investigation was made. 
 
 II. METHODS 
 
 1. SELECTION OF THE LEATHER 
 
 Russet harness leather was used in this investigation. Three 
 hides were prepared, marked butt Nos. 1,2, and 3, to study the 
 effects of different amounts of stuffing content, of animal and 
 mineral oils, and of medium and heavy tannage, respectively, on 
 the physical properties. 
 
 The method of using whole hides or double backs in preparing 
 this leather was used, so that, when split, each single back could 
 be given its special finishing treatment and when tests were made 
 the leather of the two sides compared would come from the same 
 hide. Each side was given a code letter. 
 
 (a) Description op The Leather Selected. — The hides from 
 which the leather was produced were treated in the usual manner, 
 
Harness Leather 
 
 which consisted of soaking, fleshing, liming, unhairing, handling, 
 and then laying away in the yard. The tanning materials used 
 were liquors made from chestnut-oak bark, chestnut wood, and 
 quebracho. After the tanning was completed the hides were 
 split, shaved, scoured, and bleached with a solution of soda and 
 water, sulphuric acid and water, and sumac and water. The 
 leather was then stuffed and later oiled. The finishing was done 
 by hand. 
 
 Butt No. /.— This hide received the regular tannage for this type 
 of leather and, after being split, one side (B) was stuffed with a 
 mixture of cod oil and tallow, using the amount ordinarily used 
 in the particular tannery where the leather was made. The other 
 
 
 
 
 
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 Fig. i. — Division of a side into blocks 
 
 side (A) was stuffed with a larger amount of the mixture, equal 
 approximately to that used by some tanners of black harness 
 leather. These two sides were used to study the effects of different 
 amounts of stuffing content on the physical properties. 
 
 Butt No. 2. — The leather produced by this hide was used to 
 study the effects of a medium and heavy tannage on the physical 
 properties. The hide, after receiving the regular tanning treat- 
 ment, was split and one side (C) removed, while the other side 
 (D) was allowed to remain in the vats a month longer in order to 
 receive a heavier tannage. 
 
 Butt No. 3. — This hide, after being tanned as regular russet 
 harness leather, was split and one side {E) was stuffed with a 
 mixture of 50 per cent cod oil and 50 per cent tallow. The other 
 side (F) was stuffed with a mixture of 50 per cent Breton mineral 
 oil and 50 per cent tallow. This leather was prepared to deter- 
 mine, if possible, the effects of the use of mineral and animal oils 
 on the physical properties of leather. 
 
Technologic Papers of the Bureau of Standards 
 
 (b) Preparation op Samples. — Each side of leather was di- 
 vided into 40 blocks, as shown in Fig. 1 , beginning at the butt end, 
 near the root of the tail, with block No. 1 and running across the 
 hide from back to belly. The blocks running from the butt end 
 to the shoulder end were numbered in steps of four. The size of 
 each block was approximately 8 inches in length and 7 inches in 
 width. Each was divided into samples for the various tests, as 
 
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 Fig. 2. — Division of a block into samples for the different tests 
 
 shown in Fig. 2. Three samples from each block, designated by 
 Ti, T2, and T3, were prepared for the tensile strength and elon- 
 gation tests, and three samples, designated by Bi, B2, and B3, 
 were used for the buckle tests. That part of each block used for 
 the chemical tests is designated by the letter C. Each sample 
 cut from any block carried the code letter of the bend, the number 
 of the block, and the letter representing the test for which the 
 sample was to be used. 
 
Harness Leather 
 
 2. PHYSICAL TESTS 
 
 The physical tests generally made on samples of harness leather 
 for determining the quality are for tensile strength and percentage 
 elongation. In addition, a buckle or shearing test was made. 
 
 (a) Tensile Strength. — This is the test most commonly made, 
 the results being expressed in pounds per square inch. Test 
 pieces were cut with a metal die from each individual strip. The 
 shape and size of the resulting sample are shown in Fig. 3. The 
 ends are enlarged and the central portion is reduced to a width 
 of one-half inch over a gage length of 2 inches. This shape usually 
 insures that the sample will break within the reduced section and 
 prevents tearing in the grips of the testing machine. The break- 
 ing strength, in pounds, of each sample was determined with a 
 tension machine the jaws of which separated at a rate of approx- 
 
 Fig. 3. — Shape and size of tensile strength specimens 
 
 imately 6 inches per minute. With this value and the area, as 
 determined by the width and thickness of the reduced section, the 
 tensile strength in pounds per square inch was calculated. 
 
 The breaking strength, in pounds per inch of width, was also 
 determined. There were three values for each of these properties 
 for each block and an average of the three for each property was 
 used as representing the value for the particular location on the 
 side indicated by the block number. 
 
 (6) Stretch. — The stretch, or percentage elongation, of each 
 tension test piece was determined at the breaking strength. The 
 method consisted of first marking on the reduced section parallel 
 lines 2 inches apart. A convenient method of noting the stretch, 
 used in this test, consisted of following the parallel lines on the 
 test pieces, as they separated under the tension, with a pair of 
 dividers. The elongation was then measured with a scale and the 
 percentage increase calculated. In this case also the average of 
 three values represented the value for the block. 
 
8 Technologic Papers of the Bureau of Standards 
 
 (c) Buckle Strength. — There are many parts of a harness 
 which are used in conjunction with a buckle. It is common 
 knowledge that the failure oi a particular strap or part of a har- 
 ness often occurs at one of the holes through which the tongue 
 of the buckle passes. It was thought desirable to study the 
 variation on the hide in the buckle or shearing strength of new 
 harness leather with the idea in view of showing what portions 
 of the hide might be most suitable for those straps which are 
 used with a buckle. Three samples for this test were prepared 
 from each block, as shown in Fig. 4. A hole of the proper size 
 for the buckle tongue was punched 1 inch from the end of the 
 test piece. An ordinary i>£-mch harness buckle with a tongue 
 approximately eighteen-hundredths of an inch in diameter was 
 secured to a strap which was placed in one jaw of the testing 
 
 Fig. 4. — Shape and she of buckle strength specimens 
 
 machine. The punched end of the test piece was then inserted 
 in the buckle and the free end secured in the other jaw of the 
 machine. The number of pounds required to pull the test piece 
 through the buckle was then noted. 
 
 3. CHEMICAL TESTS 
 
 (a) Stuffing Content. — It was considered possible that the 
 variation in the amount of stuffing content over the hide might 
 have some effect on the physical properties. For this reason, 
 and also to study the distribution of the stuffing content over the 
 hide, a chemical determination was made of this property for 
 each block of each side. 
 
 (b) Complete Analysis. — In order to aid in the interpretation 
 of the physical results, and also to have all the data possible for the 
 identification of the several sides, a complete chemical analysis 
 was made of each, using a composite sample prepared by taking 
 an equal quantity from each block. 
 
Harness Leather g 
 
 III. DATA AND RESULTS OBTAINED 
 1. PHYSICAL TESTS 
 
 (a) Tensile Strength. — The results of the tensile-strength 
 tests, expressed in pounds per square inch, are shown graphically 
 in Figs. 5,6, and 7. Each individual curve of the graphs represents 
 
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 the values obtained from four blocks running from the backbone 
 edge to the belly edge. The values for the tensile strength, in 
 pounds per inch of width, are shown graphically in Figs. 8,9, and 
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 inclusive, the strength is generally greater on the backbone edge, 
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 which it generally increases to either an equal or greater value 
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 strength in that part is more irregular than in the other portion, 
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 162023°— 20—2 
 
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 Technologic Papers of the Bureau of Standards 
 
 and to decrease steadily to the belly edge. A glance at Figs 8, 
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 per inch of width, for any given section of four blocks across a 
 side is generally low at the butt end, increasing in value up to 
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 where it is lowest, and then slightly increasing in value again for 
 the remaining two sections. This same variation applies to the 
 values for tensile strength, in pounds per square inch, but is not 
 so marked, due to the fact that the thickness is variable, which 
 greatly affects these values. As an illustration, considering 
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 and B in tensile strength in pounds per square inch. Fig. 8 shows 
 
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 Fig. 8. — Variation of tensile strength in pounds per inch of width over tlie side for samples 
 
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 the values of the tensile strength, in pounds per inch of width, for 
 these two sides, and it will be noted that there is not such a 
 marked difference between the values as in the case of Fig. 5. 
 The difference shown in Fig. 5 is due to the fact that the average 
 thickness over the side was greater for one than for the other. 
 
Harness Leather 
 
 ii 
 
 Thus, it is conceivable that the products of two different tanners 
 might have equal strength per inch of width, but due to the 
 different methods used the thickness of one tanner's leather might 
 be considerably less or greater than that of the other tanner, and 
 the results would be that, although the amount of fiber substance 
 was the same, the tensile strength as expressed in pounds per 
 
 
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 square inch would be quite different for the two leathers. The 
 functions of the various parts of a harness are to withstand a 
 definite strain or pull in tension which depends more upon the 
 strength of the leather per inch of width than upon the strength 
 per square inch of cross section. One tanner might furnish a 
 thick leather of the required strength and another a thinner 
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 Fig. 10. — Variation of tensile strength in pounds per inch of width over the side for samples 
 
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 to do. In view of these facts, it would seem desirable for specifi- 
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 than in pounds per square inch. 
 
 The graphs show that there is a great variation in the strength 
 in pounds per square inch over the hide, and for this reason it is 
 difficult to set a standard value. The generally accepted require- 
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 the choice, although in the two butt-end sections of all the sides 
 the value is somewhat less. The results also show that the strength 
 of the more open texture, looser, long-fibered belly and shoulder 
 portions is equal to or greater than the strength of any other 
 
 
 
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 Fig. ii. — Variation in, per cent stretch over the side for samples A and B 
 
 portions of the side. The quality of the leather from these por- 
 tions, however, is inferior to the more closely fibered and firmer 
 area extending approximately 1 5 inches on either side of the back- 
 
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 Fig. 12. — Variation in per cent stretch over the side for samples C and D 
 
 bone. Thus it will be seen that high tensile strength alone does 
 not insure the best quality of leather. 
 
 (b) Stretch. — The results of the stretch tests are shown graphi- 
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 Fig. 13. — Variation in per cent stretch over the side for samples E and F 
 
 lowest along the backbone edge of the sides and increased toward 
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 on the extreme belly edge. An interesting fact regarding the 
 stretch shows that in many cases it increases when the strength is 
 
Harness Leather 
 
 13 
 
 low and decreases when it is high. This does not occur in propor- 
 tion to the difference in strength, but is clearly shown by the fact 
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 Fig. 14. — Variation in buckle strength' over the side for samples A and B 
 
 (c) Buckle Strength. — The results of the buckle strength 
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 seen that the value for this property is generally low on the back- 
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 belly edge, after which it decreases to a minimum at the belly edge 
 for any section of four blocks running across the bend. The aver- 
 age value for the buckle strength for any section is greatest in the 
 butt end and decreases steadily to the shoulder end. 
 
 
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 Fig. 16. — Variation in buckle strength over the side for samples E and F 
 
 An effort was made to establish a percentage relation between 
 the buckle strength and tensile strength per inch of width. This 
 relation was subject to a variation of from 10 to 50 per cent in 
 one side, so that no satisfactory figure could be accepted as stand- 
 ard. The results, however, show that the belly and shoulder pro- 
 
14 
 
 Technologic Papers of the Bureau of Standards 
 
 tions are inferior to the remaining portion of the side for use in 
 straps which are to be used with a buckle. The best portion of a 
 hide for this purpose, as shown by these tests, would be that in- 
 cluded in an area about 1 5 inches either side of the backbone and 
 30 inches in length from the root of the tail. This test would 
 not be of much value when examining samples of sides for general 
 use as harness leather, but would be valuable in testing a lot of 
 straps cut for use with a buckle. Table 1 gives the average values 
 resulting from the tests. 
 
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 Fig. 17. — Variation of stuffing content over the side for samples A and B 
 
 TABLE 1.— Average Values for Thickness, Tensile Strength, Percentage Stretch 
 and Buckle Strength for each Side 
 
 
 Side 
 
 Thickness, 
 inches 
 
 Tensile strength 
 
 Per- 
 centage 
 stretch 
 
 Buckle 
 strength, 
 pounds 
 
 Butt 
 
 Pounds 
 per inch 
 ol width 
 
 Founds 
 
 per square 
 
 Inch 
 
 1 
 
 A 
 B 
 C 
 D 
 
 E 
 F 
 
 0.196 
 .178 
 .180 
 .198 
 .175 
 .172 
 
 740 
 806 
 865 
 810 
 815 
 795 
 
 3835 
 4600 
 4920 
 4130 
 4705 
 4605 
 
 30.8 
 29.0 
 31.6 
 31.1 
 28.3 
 28.2 
 
 201 
 
 1 
 
 195 
 
 2 
 
 170 
 
 2 
 
 205 
 
 3 
 
 163 
 
 3 
 
 180 
 
 
 
 2. CHEMICAL TESTS 
 
 (a) Stuffing Content. — The values for the amount of stuffing 
 content found in each block are shown graphically in Figs. 17, 
 18, and 19. The average amount for any section is least at the 
 
Harness Leather 
 
 15 
 
 butt end and then gradually increases to the shoulder, where 
 the stuffing content is greatest. The general tendency is for the 
 stuffing content to be greatest in the more open belly and shoulder 
 portions. In the case of all except bend .4 the average stuffing 
 
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 Fig. i8. — Variation of stuffing content over the side for samples C and D 
 
 content runs from 10 to 15 per cent and is shown to be fairly 
 evenly distributed over the side, except in the shoulder. When 
 a larger amount of stuffing was used, as in the case of bend A, 
 the distribution over the hide was less uniform, and the greater 
 
 
 
 
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 Fig. 19. — Var»a<ton of stuffing content over the side for samples E and F 
 
 part of the stuffing was absorbed by the belly and shoulder por- 
 tions of the hide. 
 
 (b) Complete Analysis. — A complete chemical analysis was 
 made of each side, and the results are given in Table 2. 
 
1 6 Technologic Papers of the Bureau of Standards 
 
 TABLE 2. — Results of Complete Chemical Analyses for all Sides 
 
 [Calculated to 10 per cent moisture] 
 
 
 Butt No. 1 
 
 Butt No. 2 
 
 Butt No. 3 
 
 
 Side A 
 
 SideB 
 
 Side C 
 
 SideD 
 
 Side E 
 
 SideF 
 
 
 10.00 
 .32 
 .23 
 23.35 
 32.74 
 10.05 
 2.06 
 7.99 
 
 w 
 
 .12 
 23.74 
 72.51 
 
 .50 
 
 10.00 
 
 .27 
 
 .23 
 
 10.70 
 
 39.92 
 
 10.20 
 
 2.07 
 
 8.13 
 
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 .14 
 29.03 
 72 73 
 
 .52 
 
 10.00 
 
 .43 
 
 .21 
 
 13.30 
 
 40.24 
 
 9.88 
 
 2.58 
 
 7.30 
 
 («) 
 
 .14 
 
 26.44 
 
 65.71 
 
 .35 
 
 10.00 
 
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 .22 
 
 11.46 
 
 39.81 
 
 10.66 
 
 2.16 
 
 a so 
 
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 27.93 
 70.16 
 
 .32 
 
 10.00 
 
 .31 
 
 .23 
 
 13.72 
 
 37.32 
 
 10.92 
 
 2.27 
 
 8.65 
 
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 74.93 
 
 .55 
 
 10.00 
 
 
 .31 
 
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 15.70 
 
 
 36.10 
 
 
 9.77 
 
 
 2.20 
 
 
 7.57 
 
 
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 .22 
 
 
 2& 20 
 
 
 78.12 
 
 Acidity 
 
 .37 
 
 
 
 a None. & Degree of tannage is in each case calculated from the figures given in corresponding table. 
 3. COMPARISON OF PHYSICAL AND CHEMICAL TESTS 
 
 (a) Effect of the Amount of Stuffing Content on the 
 Physical Properties. — The two sides A and B from the same 
 hide were prepared to show the effect of different amounts of 
 stuffing content on the physical properties. Side A contained 
 23.35 per cent of grease, while side B contained 10.70 per cent. 
 It is apparent from Fig. 5 that side A, which contains the higher 
 percentage of grease , is uniformly lower in tensile strength expressed 
 in pounds per square inch than is side B. The average difference 
 in strength is nearly 20 per cent and since the two sides are as 
 nearly equal in quality in every respect, except grease content, 
 as is possible to obtain it might be assumed that the difference in 
 strength is caused by the different grease contents. The higher 
 stuffing content in side A, however, caused another effect that 
 must be considered, which was to increase materially the thickness 
 of the side so that its average thickness throughout was 10 per 
 cent greater than that of side B. Hence the cross-sectional areas 
 of the various test pieces were greater for side A than for side B. 
 This fact, assuming that the same breaking load would be obtained 
 for test pieces from the same relative location on each side, would 
 cause one test piece from side A to have a lower strength per unit 
 of cross section. Thus, it would appear that about one-half, or 
 10 per cent, of the difference in strength indicated in Fig. 5 is 
 due to the difference in thickness of the two sides which was caused 
 by the different stuffing contents. The remaining 10 per cent 
 
Harness Leather 17 
 
 difference in strength may be attributed directly to the grease 
 content. 
 
 In the case of the tensile strength in pounds per inch of width 
 (Fig. 8) side B has an average value 9 per cent greater than that 
 of side A. Since the tensile strength per square inch for side B 
 was 20 per cent greater than that for side A, half of which was 
 apparently caused by the difference in thickness of the two sides, 
 the remaining 10 per cent can be attributed to the difference of 
 the two sides in the strength per inch of width. The strength in 
 pounds per inch of width is a more nearly true indication of the 
 comparative strength of different leathers, since it does not take 
 into account the thickness, which might vary for leathers on 
 account of any difference in the methods of tanning and finishing 
 by different manufacturers, and expresses the result for the same 
 amount of original hide substance regardless of the treatment of 
 the hide. 
 
 The effect of the grease content on the stretch was not appreci- 
 able, and the difference between the average values for the two 
 sides was only about 3 per cent. 
 
 There did not appear to be any appreciable effect, because of the 
 grease content, on the buckle strength. The difference between 
 the average values for the two sides was about 3 per cent. 
 
 It can not be definitely stated from the results of these tests 
 whether the variation in the grease content over the hide has any 
 effect on the strength. It is more likely that any effect produced 
 by the variation is secondary to the effect on the strength caused 
 by the location on the hide from which a sample is taken. 
 
 (b) Effect of the Degree of Tannage on the Physical 
 Properties. — Sides C and D were prepared for this test. Side D 
 was tanned the longer time, but the analysis of both show that 
 side C had reached that stage in the tanning process beyond which 
 the increase in the degree of tannage is slow. This is shown by 
 the fact that the difference in the degree of tannage figures for 
 the two sides was approximately 5. 
 
 The tensile strength in pounds per square inch (Fig. 6) for side C 
 was uniformly greater throughout than for side D. This result 
 is what would be expected, since side C, having the lighter tannage, 
 was relatively nearer to the raw-hide condition in which condition 
 the strength would be greatest. The average strength, in pounds 
 per square inch, for side C was approximately 20 per cent greater 
 than for side D, but, as was the case with sides A and B, side D 
 was also 10 per cent thicker than side C, thus causing its average 
 
1 8 Technologic Papers of the Bureau of Standards 
 
 tensile strength in pounds per square inch to be considerably less 
 for the same amount of original hide. The average strength per 
 inch of width for side C was 7 per cent greater than for side D. 
 Although the degree of tannage values for these two sides was not 
 very different, it would appear that the lower strength of side D 
 is due to the longer time in the tanning process. 
 
 The stretch of the leather did not appear to be materially 
 affected by the different lengths of tannage, the average value 
 for the stretch being nearly the same in both cases. 
 
 The average buckle strength for side D (Fig. 15) was approxi- 
 mately 20 per cent greater than the value for side C. Thus, it 
 would appear that a long-time tannage would produce a more 
 solid and firmer leather, which would resist a shearing action to 
 a greater degree than a leather tanned for a shorter period of time. 
 
 (c) Effect of Animal and Mineral Oils on the Physical 
 
 Properties. — Sides E and F were prepared for this test. The 
 
 average tensile-strength and stretch values were nearly the same 
 
 for both sides, but the average buckle strength of side F was 
 
 approximately 10 per cent greater than the average value for 
 
 side E. This may be on account of the fact that, although both 
 
 sides were tanned for the same length of time, side F had a higher 
 
 value for the degree of tannage. The results indicate that there 
 
 is no essential effect upon the physical properties of new leather 
 
 caused by the use of mineral instead of animal oils in the stuffing 
 
 content. 
 
 IV. CONCLUSIONS 
 
 Although this investigation was somewhat limited in its scope, 
 the following general conclusions have been drawn, based upon the 
 results obtained with the material used in these experiments: 
 
 1. That the amount of stuffing content affects the tensile 
 strength of the leather and that there is a point beyond which 
 the amount of stuffing content used does not add to the strength 
 and may actually serve to decrease it. 
 
 2. That the tensile strength is greater for leather tanned a 
 short time than for leather given a long-time tannage, and that 
 the degree of tannage also affects the- firmness of the leather, the 
 longer-time tannage producing leather more resistant to shear when 
 used with a buckle. 
 
 3. That the use of the type of mineral oil with which side F 
 was stuffed does not affect the physical properties of new leather 
 in a manner different than that caused by the use of cod oil. 
 
 Washington, October 27, 1919. 
 
LIBRARY OF CONGRESS 
 
 015 992 294 7 
 
 
 
LIBRARY OF CONGRESS 
 
 015 992 294 7 m 
 
 Hollinger Corp. 
 P H 8.5