ASTM D8137-18(2023)
(Practice)Practice for Accelerated Aging of Leather
Practice for Accelerated Aging of Leather
SIGNIFICANCE AND USE
6.1 A substantial difficulty in using leather in applications requiring very long service lives is estimating how well a particular leather will actually hold up in service. Such applications may include use in musical instruments such as pipe organs, bookbinding leathers, etc. Use of leather in pipe organs in the past (prior to approximately 1930) demonstrated service lives frequently over 100 years, and the consequences of short service lives can result in extremely costly repairs. Many post-1930 leathers have had short service lives (as little as 15 years) due to the use of various more modern tannages and processing methods. Identifying exactly what tannage and processing was used in a particular leather and how successful this tanning and processing was can be very difficult. Failure of bookbinding and upholstery leathers formed the impetus for extensive work by leather chemists in the 1940s to identify tests that could be used to verify the durability of leather samples. Early studies by Cheshire3 and Frey & Beebe4 resulted in tests relating the rate of deterioration of leathers having known durabilities from long-term storage of samples, to the deterioration experienced by laboratory exposure of specimens to known contents of acid gases in air or oxygen. They were considered to be applicable to leathers having a wide range of tannages and processing. Later work published by Piltingsrud & Tancous5 described their modifications to those tests. Further work directed towards verifying the durability of leathers used in pipe organs resulted in the practice described in this document. The appropriateness of its use for any given leather samples must be determined by the leather chemists utilizing the practice. This practice may not be applicable for leathers having unusual tannages or treatments. Estimates of service lives made using this practice are speculative, as it would take many decades of natural aging to verify the results (see comments in Section 11).
SCOPE
1.1 This practice is based on studies relating the rate of deterioration of leathers having known durabilities from long-term storage of samples, to the deterioration experienced by laboratory exposure of specimens to known contents of acid gases in air or oxygen. This is accomplished by measuring the deterioration (reduction in tensile strength) of leather specimens when they are subjected to exposure to a mixture of air, moisture and sulfur dioxide at a given temperature and pressure and for a given exposure time. The loss of tensile strength of the specimens resulting from this exposure is compared to that experienced by a variety of leathers having various tannages and having historically long and short service lifetimes. The initial tensile strength and the degree of loss of tensile strength is related to what service life can be anticipated from a given leather.
1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D8137 − 18 (Reapproved 2023)
Practice for
Accelerated Aging of Leather
This standard is issued under the fixed designation D8137; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope D2209 Test Method for Tensile Strength of Leather
1.1 This practice is based on studies relating the rate of
3. Terminology
deterioration of leathers having known durabilities from long-
3.1 For definitions of leather terms used in this Practice
term storage of samples, to the deterioration experienced by
refer to Terminology D1517.
laboratory exposure of specimens to known contents of acid
gases in air or oxygen. This is accomplished by measuring the
4. Reagents
deterioration (reduction in tensile strength) of leather speci-
mens when they are subjected to exposure to a mixture of air,
4.1 Sulfur Dioxide (SO ), Anhydrous, 99.9 % pure.
moistureandsulfurdioxideatagiventemperatureandpressure
4.2 Air, From compressor, filtered, stored at ~21°C (satu-
and for a given exposure time. The loss of tensile strength of
rated water vapor conditions) 90 psi to 100 psi delivery
the specimens resulting from this exposure is compared to that
pressure.
experienced by a variety of leathers having various tannages
and having historically long and short service lifetimes. The
5. Summary of Practice
initial tensile strength and the degree of loss of tensile strength
5.1 Specimens are prepared and placed in a pressure cham-
is related to what service life can be anticipated from a given
ber containing known or constant quantities of air, moisture
leather.
and SO . They are held in the chamber at a constant tempera-
1.2 This standard does not purport to address all of the
ture for a given time period. After that processing, the tensile
safety concerns, if any, associated with its use. It is the
strengths of the specimens are measured along with the tensile
responsibility of the user of this standard to establish appro-
strengths of unprocessed specimens of the same leather. The
priate safety, health, and environmental practices and deter-
loss of tensile strength resulting from the processing relative to
mine the applicability of regulatory limitations prior to use.
that of the unprocessed specimens (%) is determined and may
1.3 This international standard was developed in accor-
be directly compared to that of other leathers considered for an
dance with internationally recognized principles on standard-
application. Where applicable, the results may also be consid-
ization established in the Decision on Principles for the
ered as the basis for projected service lifetimes as shown in
Development of International Standards, Guides and Recom-
Section 11.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
6. Significance and Use
2. Referenced Documents 6.1 A substantial difficulty in using leather in applications
requiring very long service lives is estimating how well a
2.1 ASTM Standards:
particular leather will actually hold up in service. Such
D1517 Terminology Relating to Leather
applications may include use in musical instruments such as
D1610 Practice for Conditioning Leather and Leather Prod-
pipe organs, bookbinding leathers, etc. Use of leather in pipe
ucts for Testing
organs in the past (prior to approximately 1930) demonstrated
D1813 Test Method for Measuring Thickness of Leather
service lives frequently over 100 years, and the consequences
Test Specimens
of short service lives can result in extremely costly repairs.
Many post-1930 leathers have had short service lives (as little
This practice is under the jurisdiction ofASTM Committee D31 on Leather and
as 15 years) due to the use of various more modern tannages
is the direct responsibility of Subcommittee D31.05 on Upholstery.
and processing methods. Identifying exactly what tannage and
Current edition approved Jan. 1, 2023. Published January 2023. Originally
processing was used in a particular leather and how successful
approved in 2018. Last previous edition approved in 2018 as D8137-18. DOI:
10.1520/D8137-18R23
this tanning and processing was can be very difficult. Failure of
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
bookbinding and upholstery leathers formed the impetus for
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
extensive work by leather chemists in the 1940s to identify
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. tests that could be used to verify the durability of leather
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8137 − 18 (2023)
3 4
samples. Early studies by Cheshire and Frey & Beebe 7.6 Compressor-air Storage Tank System—A typical
resulted in tests relating the rate of deterioration of leathers compressor-air storage tank system having a tank volume of at
having known durabilities from long-term storage of samples, least 100 L is quite sufficient. Make sure that there is some
to the deterioration experienced by laboratory exposure of water in the bottom of the tank (normal for most compressor-
specimens to known contents of acid gases in air or oxygen. air storage tanks that are operated frequently) so that air stored
They were considered to be applicable to leathers having a in the tank at room temperature comes to equilibrium near
wide range of tannages and processing. Later work published 100 % relative humidity at laboratory room temperature. This
by Piltingsrud & Tancous described their modifications to helps to ensure that the initial humidity in the RPVduring runs
those tests. Further work directed towards verifying the dura- is consistent run to run. The day before the test is
bility of leathers used in pipe organs resulted in the practice accomplished, the air source should be checked to ensure that
described in this document. The appropriateness of its use for there is an adequate pressure to be able fill the RPV to 100 psi
any given leather samples must be determined by the leather and that there is sufficient time before the run (at least 12 h) for
chemists utilizing the practice. This practice may not be the air in the tank to reach room temperature and humidity
applicable for leathers having unusual tannages or treatments. equilibrium. The tank pressure is normally set to 120 psi
Estimates of service lives made using this practice are allowingsufficientpressuretoregulatedowntothedesired100
speculative, as it would take many decades of natural aging to psi in the RPV.
verify the results (see comments in Section 11).
8. Specimens
7. Apparatus
8.1 Cut the specimens using a ⁄4 by 2 in. cutting die. Cut 15
samples for aging test if possible (see Fig. 1). Cut another 15
7.1 The reaction pressure vessel (RPV) is made up of 316
specimens for control reference. Specimens need to be cut with
Alloy Stainless Steel, Schedule 10, 3 in. pipe components
the same orientation parallel or perpendicular to the backbone
welded together. These consist of two end caps (one end cap
of the hide and in a similar location such that the specimens
has a 1 in. hole in it), a 12 in. section of pipe, and a 1 in.
have similar properties. Leather should be conditioned in
National Pipe Thread (NPT) union (cut in half). These are
accordance with Test Method D1610.
welded together using inert gas welding and alloy 316 stainless
steel filler rod. 8.2 Process only one type of leather in the RPV at a time.
7.2 The RPV Valve—The valve used has ⁄8 in. NPT threads
9. Procedure
and is made of alloy 316 stainless steel. It is a positive shutoff
9.1 Assembly of the Reaction Pressure Vessel (RPV):
needle valve rated for pressures up to 1000 psi. It is used with
3 9.1.1 Make sure that no foreign materials are present in the
a1-to ⁄8-in. NPT 316 stainless steel reducer bushing.
interior of the RPV. If there are any residues present or you are
7.3 RPV Pressure Gauge—The gauge used for measure-
not sure if the vessel is clean, use cleaning methods you would
ments of pressure in the RPV and for filling measurements
ordinarily use for stainless steel laboratory ware used for
must have a range up to 125 psi, and an accuracy of 62.0 psi.
analytical chemistry purposes.
9.1.2 Make sure the interior of the RPV is dry by placing it
7.4 Die—Leather cutting punch type for test strip ⁄4 in.
in the oven (at 60 °C) for 15 min, without the valve installed.
wide by 2 in. long.
CooltheRPVtoroomtemperaturebeforeplacingspecimensin
7.5 Oven—The RPV must be kept at a constant temperature
it.
throughout the exposure period of the test. This is best
9.1.3 Place the specimens to be treated into the RPV.
accomplished by placing the RPV in an oven having mechani-
9.1.4 Using polytetrafluoroethylene (PTFE) tape sealant,
cal air circulation, and with an accurate electronic temperature
prepare the valve head threads for assembly into the RPV.
control with the capability of maintaining a temperature of
Make sure all old sealant is removed using a stainless steel
approximately 61.0 °C, and a uniformity of 64.0 °C. The
brush before applying the PTFE tape. The PTFE tape is
uniformity isn’t quite as important as the stability, as the
wrapped around the threads, several layers thick, depending on
thermal conductivity and thermal capacity of the RPV aids in
the thickness of the tape (see Fig. 2). Methods used should
providing thermal uniformity inside the RPV. The temperature
result in leak free joints (see section on leak checking).
calibration of the oven should be checked using a thermo-
couple thermometer. Many commercial laboratory ovens are
capable of this performance.
Chesire, A., “The Aging of Leather,” Journal of the International Leather
Trades Chemists, June 1946, Vol. 30, No. 6, pp. 134-166.
Frey, R. W., and Beebe, C. W., “A Proposed Standard Gas Chamber for
Accelerated Aging of Leather,” The Journal of the American Leather Chemists
Association, 1940, Vol. 35, pp. 180-192.
Piltingsrud, H. V., and Tancous, J., “The Development of a Standard Acceler-
ated Aging Test for Measuring the Durability of Leathers Used in Musical
Instruments,” The Journal of the American Leather Chemists Association, 1987,
Vol. 82 (9), pp. 277-310. FIG. 1 Specimens for Aging Test
D8137 − 18 (2023)
FIG. 2 Preparing the Valve Head Threads
9.1.4.1 Insert valve head into the RPV. Threads must be
tightened sufficiently so that there is no leakage when tested
FIG. 4 The Pressure Gauge and Filling Port
later by the soap bubble method. Normally tightening is
accomplished by applying a locking chain clamp around the
body of the RPV and a 12 in. crescent wrench on the 1 ⁄8 in.
hexheadofthevalveheadassembly(seeFig.3).Normally,the
assembly is placed on the floor and tightened as needed (as
tight as an average person can tighten).
9.1.5 Attach the pressure gauge and the filling port (see Fig.
4)tothetopoftheRPVvalveusingPTFEtapeasasealant(see
Fig. 5)
9.2 Filling the RPV with SO :
9.2.1 Remove the ⁄4 in. NPT plug from the SO tank. Insert
the mating connector into the threaded port on the SO tank
usingPTFEtapeasasealant.Insertpurgingconnector(afitting
that mates with the connector on the hose, and has a through
passage allowing gas to escape) into the opposite end of the
SO filling hose.
9.2.2 Place the RPV, SO tank, and filling apparatus in a
fume hood that has been determined to be suitable for working
FIG. 5 Attaching the Pressure Gauge and Filling Port to the RPV
with the SO used in this test. Open the SO tank valve slightly
2 2
allowing the SO to purge the air from the interior of the SO
2 2
filling hose (see Fig. 6). Close the SO tank valve and remove
the purging connector from the SO filling hose.
9.2.3 Connect the SO filling hose to the filling port on the
RPV, making sure the gauge reads zero before connecting to
the SO filling hose (See Fig. 7).
9.2.4 Open the RPV valve completely (wide open) and
slowly open the SO tank valve to the point resulting in a
pressure increase on the pressure gauge of approximately 1 psi
FIG. 6 Purging the Air from the Interior of the SO Filling Hose
every 2 s. Allow the pressure in the RPV to increase to
14.7 psi 6 0.2psi.Thenrapidlyclosethevalveonthetankand
the RPV.
9.2.5 Disconnect the RPV from the SO filling hose.
9.3 Filling the RPV with Compressed Air:
9.3.1 Briefly place a purging port in the compressed air tank
FIG. 3 Tightening of the Valve Head outlet port to allow a small amount of air to bleed out of the
D8137 − 18 (2023)
9.4.1 Use a soap water solution for leak checking. Apply
soap water solution to the exposed threads of the RPV and the
valveassembly(seeFig.9).Usealiquiddishwashingdetergent
diluted to approximately a 10 % solution with water.
9.4.2 Carefully examine the bubble size for growth, which
could indicate a leak.
9.4.3 With a drop of soap solution on your finger tip attempt
to lace a soap water film over the exposed port of the valve.
Any increase in the size of the film would indicate an internal
leak of the valve. Any detected leaks should be corrected.
Possible causes could be insufficient tread sealant, insufficient
tightening of the joints, a defective valve, etc.
9.4.4 Apply new PTFE tape to the exposed threads on the
valve and place the stainless steel cap on the valve outlet (see
Fig. 10).
9.5 Placing the RPV in the Oven:
9.5.1 Preheat the oven to the desired operating temperature
(60 °C) before placing the RPV in the oven. The oven can be
any oven with forced air circulation that can maintain the RPV
at 60 °C 6 1 °C. Shown in Fig. 11 and Fig. 12 is a special
FIG. 7 Connecting to the SO Filling Hose
purpose oven made for the task. Many laboratory ovens with
forced air circulation should be sufficient.
tank. This will allow you to see where the pressure regulator is 9.5.2 Place the RPV in the oven as shown in Fig. 11.
actually set, in case there has been leakage through the
9.6 Aging Process:
regulator building up pressure on the lower pressure side.
9.6.1 The RPV is left at the desired operating temperature
Make sure that the pressure regulator is set several psi below
for 168 h (1 week).
the 100 psi desired setting so the pressure can then be raised up
9.6.2 The RPV should be rotated 180° ever
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