ASTM D2210 Mullen Test for Leather Grain Stretching Crack & Extension

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ASTM D2210 Standard | Mullen Test Machine for Leather Grain Crack & Extension Measurement | UnitedTest

UnitedTest manufactures ASTM D2210-compliant Mullen burst testers for leather factories, footwear labs and furniture leather inspection facilities worldwide.

ASTM D2210 Standard Test Method for Grain Crack and Extension of Leather by the Mullen Test measures two core leather mechanical metrics: grain crack resistance (burst pressure when leather surface cracks under biaxial stretch) and extension stretch percentage at grain failure.

This standard applies exclusively to thin finished light leathers including shoe uppers, garment leather, glove leather and upholstery leather, and excludes wet blue chrome-tanned crust leather. Our Mullen tester fully meets ASTM D2210 biaxial stretching test rules to generate accurate grain crack pressure and stretch data for leather product quality control.

Core Test Principle

A 3 × 3 in (76 × 76 mm) leather square is clamped between two annular rings so the flesh side contacts a rubber diaphragm. Hydraulic pressure (glycerin) is applied under the diaphragm, pushing it—and the leather—upward into a spherical bulge. As pressure rises:

The leather grain elongates multi-directionally (simulating lastingover a shoe last).

At a critical pressure, first cracks appear on the grain surface → recorded as cracking pressure.

The bulging height his measured independently to compute percent extension.

Grain cracking is a failure-under-elongation mode, distinct from full-thickness burst. Cuts, scratches, and defects concentrate stress and cause large scatter.

Test Specimen (Test Piece) Specifications

Specimen geometry: Square leather piece 3 in × 3 in (76 mm × 76 mm), cut from representative production leather batches.

Defect prohibition: No mechanical damage, scratches, grain blemishes, scars, or uneven finishing on the central test area.

Pre-test conditioning: All specimens conditioned fully per ASTM D1610 environmental conditioning practice before testing.

Test Equipment of ASTM D2210 Mullen Test for Leather Grain Stretching Crack & Extension

Mullen Testing Machine	Recommend UnitedTest Hydraulic Burst Tester, Mullen Testing Machine, Mullen Tester, motor-driven hydraulic tester with dual matte annular clamping plates. Upper clamping ring circular opening: 1.240 ±0.010 in (31.50 ±0.25 mm) diameter; Lower diaphragm plate thickness: 0.219 ±0.003 in (5.56 ±0.08 mm), identical opening diameter as upper ring; All contact edges with leather/diaphragm rounded to radius ≤0.025 in (0.64 mm) to avoid cutting specimens.
Gage for Extension Measurement	Mounted via screw shaft or side platform, flat anvil and presser foot contacting the leather grain surface. Resolution reads directly to 0.001 in (0.03 mm) for precise deflection height recording.
Rubber Diaphragm	Thickness: 0.034 ±0.002 in (0.86 ±0.05 mm). Mounted beneath the lower plate so its top surface sits below the clamping plane before hydraulic pressurization.
Bourdon Tube Pressure Gauge	Full-scale accuracy within 1% of maximum capacity. Test readings must fall between 25%–75% of the gauge’s full range to eliminate measurement error.
Hydraulic Pressure Generation System	Piston pump delivering glycerin fluid to the pressure chamber, two standardized pressurization rates based on tester configuration: Tester only measuring cracking pressure: Pump flow rate 170 ±10 mL/min; handwheel crank speed ~30 rpm Tester measuring both crack pressure + extension: Pump flow rate 15 ±2 mL/min; handwheel crank speed ~3 rpm Pumping/cranking speed must be documented in final test reports.

Test Parameters & Stipulations

Parameter	Requirement
Clamping opening	1.240 ± 0.010 in (31.50 ± 0.25 mm)
Diaphragm thickness	0.034 ± 0.002 in
Pumping rate	170 ± 10 mL/min (crack only) / 15 ± 2 mL/min (crack + extension)
Pressure gauge use range	25–75 % of full scale
Cracking pressure reporting	Nearest 5 psi (35 kPa)
Extension reporting	Nearest 0.001 in, then converted to % via 2.56 h² × 100 (valid for h = 0.2–0.5 in / 5.08–12.70 mm, Tables A1.1–A1.2)
Pump-speed log	To nearest 10 %; hand-crank rpm also recorded
Precision (same operator, same skin, duplicate adjacent specimens)	Not suspect unless CV exceeds values in §10.1.1; two-lab duplicate: averages should not differ > 5 %

Step-by-Step Standard Test Procedures of ISO 2758 Paper bursting strength test

Measure specimen thickness at three positions within the central test circle, calculate average thickness.

Mount the leather specimen with its flesh side fully contacting the rubber diaphragm.

Clamp the specimen tightly between upper and lower rings without crushing or damaging the leather grain.

Lower the dial gage presser foot onto the flat grain surface and zero the dial reading.

Activate the hydraulic pump to steadily increase fluid pressure at the specified flow rate.

Immediately stop the machine the moment the first visible crack appears on the leather grain surface.

Record the maximum cracking pressure value from the Bourdon gauge and the deflection height h from the dial gage.

Convert h to percentage stretch using the mathematical formula or Annex A1 lookup tables.

Applicable Industry Fields

ASTM D2210 is the primary quality control standard for light finished leather across these sectors:

Footwear manufacturing: Shoe upper leather quality inspection, verifying lasting performance during shoe assembly

Apparel & fashion leather: Garment leather, leather jacket, skirt, and fashion accessory material qualification

Glove production: Dress leather gloves, fashion glove raw material batch acceptance

Furniture & automotive upholstery: Sofa, chair, car interior leather durability assessment

Leather laboratory & third-party inspection: Batch incoming material acceptance, finished product service-life evaluation, supplier specification compliance verification

Leather tanneries: In-process production control for finishing and retanning formulation validation

The test predicts real-world failure risk: leather that cracks at low pressure or low stretch will split, tear, or show surface damage during stretching, sewing, and shaping in manufacturing or end use.

Related standard:

ISO 3379	Leather – Determination of distension and strength of surface (ball burst test) Global counterpart to ASTM D2210, identical spherical biaxial stretching principle for grain crack resistance
QB/T 2712	Leather-Physical and mechanical tests-Determination of distension and strength of grain-Ball burst test
DIN 53325	German standard for leather spherical distension test
ASTM D3786	(textile Mullen burst test): Same Mullen hydraulic burst mechanism, but formulated for woven fabrics, not leather grain performance
ASTM D2209	Standard Test Method for Tensile Strength of Leather
ASTM D2211	Standard Test Method for Elongation of Leather
ASTM D2212	Standard Test Method for Slit Tear Resistance of Leather
ASTM D4704	Standard Test Method for Tearing Strength, Tongue Tear of Leather
ISO 2758	Applies to thin paper only, burst range 70–1400 kPa, smaller clamping hardware;
ASTM D2210	Standard Test Method for Grain Crack and Extension of Leather by the Mullen Test
ISO 2759	Board - Determination of bursting strength
ISO 3036	Board — Determination of puncture resistance using a pendulum device

Importance of ASTM D2210 Testing for Leather Materials

Predict manufacturing failure risk: Shoe lasting, upholstery stretching, and garment tailoring apply biaxial tension to leather grain. The test identifies low-quality leather prone to surface cracking during production, reducing scrap, rework, and production cost loss.

Standardized supplier specification acceptance: Creates universal quantitative metrics (crack psi, stretch %) for tanneries, brands, and factories to align material quality requirements, eliminating subjective visual inspection bias.

End-user service performance evaluation: Low grain crack resistance leads to premature surface splitting on shoes, furniture, and clothing during daily wear/use. Test data forecasts product service life and customer complaint risks.

Keywords: UnitedTest ASTM D2210 leather tester, ASTM D2210 Mullen test grain crack extension machine, light finished leather biaxial stretch burst testing equipment, shoe upper garment upholstery leather grain crack resistance tester, ASTM D2210 leather stretch percentage inspection bench, Mullen burst tester excluding wet blue crust leather

Cardboard Puncture Resistance Tester used to measure the puncture resistance strength of corrugated cardboard. A wide range of applications and is an essential everyday tool for cardboard, carton production, research, and inspection in enterprises and departments.

Q1: What is the core purpose of ASTM D2210 test?

A: This standard Mullen test measures two key leather properties: grain cracking resistance (burst pressure when leather surface cracks under biaxial stretch) and percentage extension (stretch rate before grain failure). It only applies to light finished leather like shoe uppers, garment, glove and upholstery leather, and excludes wet blue leather. It simulates biaxial stretching stress leather receives during shoe lasting, furniture forming and garment processing.

Q2: Why is ASTM D2210 critical for leather manufacturers and brands?

A: It predicts production defects: Leather with low crack pressure will crack or split during shoe lasting, upholstery stretching, cutting and sewing, reducing scrap rate and rework cost.

Provides objective numerical indicators (cracking pressure in psi, stretch %) instead of subjective visual judgment for raw material incoming inspection and supplier quality agreements.

Evaluates end-use durability: Low grain ductility leads to premature surface cracking on footwear, leather clothes and sofas in daily use, helping brands reduce customer complaints.

Supports tannery R&D: Tests how retanning, fatliquor and surface finishing change leather flexibility, guiding chemical formula adjustment.

Meets North American market quality certification requirements for leather goods export.

Q3: What types of leather cannot be tested with ASTM D2210?

A: Wet blue leather is explicitly excluded. Thick heavy leather, full crust leather without finishing, and leather with obvious scars, deep scratches or mechanical damage on the test area are also unsuitable, as defects will concentrate stress and cause severely distorted test data.

Q4: What specimen size is required for ASTM D2210?

A: Test specimens must be cut into 3 × 3 inch (76 × 76 mm) square pieces, free of surface blemishes, cuts and damage in the central circular test zone.

Q5: What is the difference between ASTM D2210 and ISO 3379?

A: Both use spherical biaxial bulging to test grain crack and stretch performance, which makes them equivalent core test methods. Key differences:

ASTM D2210 uses imperial psi as standard unit, ISO 3379 fully adopts metric units;

Hydraulic pressurization flow rates and clamping ring dimensional tolerances have slight numerical gaps;

ASTM D2210 is the mandatory standard for North American leather market inspection, while ISO 3379 is widely used in EU, Asia and most global markets.

Q6: What is the difference between the two hydraulic pressurization rates in the standard?

A: Two pump speeds are specified based on tester model:

Basic Mullen tester (only record cracking pressure): Liquid pumping rate 170±10 mL/min or handwheel 30 rpm.

Advanced tester (measures both crack pressure and extension): Pump rate 15±2 mL/min or handwheel 3 rpm.

Testing speed must be recorded in the final report; results from different speeds cannot be cross-compared directly.

Q7: How to calculate percentage stretch from measured deflection height h?

A: The mandatory formula from Annex A1: Stretch (%) = 100 × 2.56 × h². The standard also provides two conversion tables for quick lookup: one for inch h values (0.2–0.5 in) and one for mm h values (5.08–12.70 mm), eliminating manual calculation errors.

Q8: Why place the leather flesh side against the rubber diaphragm instead of grain side?

A: Hydraulic pressure pushes the diaphragm upward to bulge the leather outward. Flesh side contact ensures uniform force transfer from the flexible rubber base to the whole leather layer, so tensile stress evenly distributes on the outer grain surface. If grain touches the diaphragm, local friction and uneven stretching will trigger premature false cracking and invalid test results.

Q9: When should we stop the machine during testing?

A: Immediately shut down the hydraulic pump the moment the first tiny visible crack appears on the leather grain surface. If testing continues after initial cracking, the recorded pressure and deflection height will be higher than real grain failure value and fail to reflect genuine leather surface ductility.

Q10: Can this test data replace uniaxial tensile test (ASTM D4944) results?

A: No, they are complementary rather than interchangeable. ASTM D2210 simulates biaxial stretching (real lasting/upholstery forming stress), focusing on surface grain cracking. ASTM D4944 uniaxial tensile test only pulls leather in one direction, mainly measuring overall breaking strength of the leather body, without evaluating grain surface failure risk. Both tests are often required together for full leather mechanical performance assessment.

Q11: What causes large deviation between replicate test specimens from the same leather batch?

A: Common root causes:

Specimens contain hidden scars, insect bites or uneven finishing coatings;

Inconsistent clamping tightness leading to partial slippage during pressurization;

Aged, deformed rubber diaphragm causing uneven bulging;

Specimens not fully conditioned per ASTM D1610;

Different pumping speeds used between replicates;

Uneven thickness distribution across the leather hide.

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