ASTM C424-93(2020)

Standard Test Method for Crazing Resistance of Fired Glazed Whitewares by Autoclave Treatment

SIGNIFICANCE AND USE
2.1 This test method is particularly useful for porous materials that can exhibit moisture expansion.  
2.2 This test method is a primary test method that is suitable for use in specifications, quality control, and research and development. It can also serve as a referee test method in purchasing contracts or agreements.
SCOPE
1.1 This test method covers the determination of the crazing resistance of fired glazed whitewares using the autoclave treatment and under the conditions specified in this test method.  
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.  
1.3 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.  
1.4 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

• Status: Published
• Publication Date: 31-Oct-2020
• ICS: 81.060.20 - Ceramic products
• ICS: 97.040.60 - Cookware, cutlery and flatware
• Technical Committee: C21 - Ceramic Whitewares and Related Products
• Drafting Committee: C21.03 - Methods for Whitewares and Environmental Concerns

Overview

ASTM C424-93(2020), titled "Standard Test Method for Crazing Resistance of Fired Glazed Whitewares by Autoclave Treatment," establishes a test method for evaluating the resistance of glazed whiteware ceramics to crazing-fine, crack-like lines on the glazed surface-by means of an autoclave treatment under specific conditions. Developed by ASTM International, this standard ensures uniformity in assessing the durability of ceramic products when exposed to moisture expansion and high-pressure steam.

The test outlined in ASTM C424-93(2020) is especially relevant for quality assurance, specification compliance, research and development, and as a referee method in purchasing agreements for ceramic products.

Key Topics

• Crazing Resistance: Focuses on measuring the ability of fired glazed whitewares-such as tiles, tableware, and sanitary ware-to resist crack development under standardized high-pressure steam conditions.
• Autoclave Test Method: Describes preparation, testing procedure, pressure schedule, and reporting requirements using an autoclave with distilled water and controlled steam pressure increments.
• Specimen Preparation: Specifies dimensions and number of test pieces required for conformance to the standard.
• Examination Techniques: Outlines procedures for inspecting samples under oblique lighting and with suitable inks or dyes to detect any visible crazing.
• Reporting Criteria: Details all reporting requirements including specimen identification, ink or dye used, the number of failures at each pressure, and calculation of average failure pressure.

Applications

• Quality Control: Manufacturers use ASTM C424-93(2020) to verify production batches of glazed ceramics meet specified crazing resistance, reducing customer complaints and warranty claims.
• Material Specification: The method serves as a reference point in sales contracts, ensuring consistent evaluation criteria for both buyers and sellers of ceramic products.
• Research and Development: Useful for testing new ceramic formulations or glazes, allowing producers to optimize materials for maximum durability and performance.
• Product Certification: Regulatory agencies and third-party certifiers may require compliance with this standard to ensure product safety, longevity, and suitability for intended use environments.
• Dispute Resolution: Functions as a referee test when resolving disputes regarding material performance in supply agreements.

Related Standards

• ASTM C21: General standards for ceramic whitewares and related products, recommended for reference in comprehensive ceramic material evaluation.
• ISO 10545-11: International standard concerning the determination of crazing resistance for ceramic tiles, which can be cross-referenced for global trade.
• ASTM C370: Standard test method for moisture expansion of fired whiteware products, supplementing the assessment of ceramic durability.

By adhering to ASTM C424-93(2020), organizations in the ceramics industry benefit from a rigorous, repeatable, and internationally recognized method for validating the crazing resistance of glazed whitewares. This standard not only facilitates improved product quality and customer satisfaction but also streamlines procurement and compliance across domestic and international markets. For more information or to obtain the official document, visit the ASTM International website.

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: C424 − 93 (Reapproved 2020)
Standard Test Method for
Crazing Resistance of Fired Glazed Whitewares by
Autoclave Treatment
This standard is issued under the fixed designation C424; 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 racy of 65 psi (34 kPa), and a source of heat of sufficient
capacity to ensure a constant steam pressure within the
1.1 This test method covers the determination of the crazing
autoclave.
resistance of fired glazed whitewares using the autoclave
treatment and under the conditions specified in this test
4. Number of Specimens
method.
4.1 The crazing test shall be made on at least ten identical
1.2 The values stated in inch-pound units are to be regarded
uncut specimens having facial dimensions up to and including
as standard. The values given in parentheses are mathematical
6 by 6 in. (152 by 152 mm) or 6 by 8 in. (152 by 200 mm). For
conversions to SI units that are provided for information only
larger specimens, specifically tile products, five samples will
and are not considered standard.
suffice and these may be cut to facilitate entry into the
1.3 This standard does not purport to address all of the autoclave. However, all cut pieces should be as large as
safety concerns, if any, associated with its use. It is the possible and all cut pieces are to be tested.
responsibility of the user of this standard to establish appro-
5. Procedure
priate safety, health, and environmental practices and deter-
5.1 Placement of Specimens in the Autoclave—Place a
mine the applicability of regulatory limitations prior to use.
sufficientamountofdistilledwaterintheautoclavesothatafter
1.4 This international standard was developed in accor-
the test a slight excess of water will remain. Place all
dance with internationally recognized principles on standard-
specimens on a suitable support at least 2 in. (51 mm) above
ization established in the Decision on Principles for the
the water line within the autoclave at room temperature. Fasten
Development of International Standards, Guides and Recom-
the autoclave head securely in place.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
5.2 OperationofAutoclave—Gradually heat the water in the
bottom of the autoclave. Keep the blow-off valve open for
2. Significance and Use
several minutes after steam begins to escape, thereby expelling
2.1 This test method is particularly useful for porous mate-
most of the air. After closing the blow-off valve, increase the
rials that can exhibit moisture expansion.
steam pressure at a uniform rate until the desired pressure is
reached within a period of not less than 45 min nor exceeding
2.2 This test method is a primary test method that is suitable
1 h. Apply sufficient heat to maintain the indicated pressure
for use in specifications, quality control, and research and
constant (62 psi (14 kPa)) for an additional hour. Shut off the
development. It can also serve as a referee test method in
heat source and release the steam pressure immediately by
purchasing contracts or agreements.
opening the blow-off valve.
3. Apparatus
5.2.1 If it is desirable to ascertain whether failure occurs as
a result of rehydration only, the blow-off valve should be
3.1 Autoclave—An autoclave built for a steam pressure of at
cracked only and the steam released slowly over a period of
least 275 psi (1.9 MPa), and preferably with sufficient capacity
30 min. If this method of steam release is used, the report shall
to contain at least ten specimens. The apparatus shall be
so state.
equipped with a safety valve, a blow-off valve, pressure gauge
...