ASTM D660-93(2019)

Standard Test Method for Evaluating Degree of Checking of Exterior Paints

SIGNIFICANCE AND USE
3.1 Since checking is not easily recognizable, this test method is intended to provide, through definition and illustrations, a means of evaluating the degree of this film failure.
SCOPE
1.1 The illustrated reference standards included in this test method are representative of degrees and types of checking of exterior paint films. These standards are primarily intended for comparative evaluation.  
1.2 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: 30-Sep-2019
• ICS: 87.040 - Paints and varnishes
• Technical Committee: D01 - Paint and Related Coatings, Materials, and Applications
• Drafting Committee: D01.25 - Evaluation of Weathering Effects

Relations

• Replaces: ASTM D660-93(2011) - Standard Test Method for Evaluating Degree of Checking of Exterior Paints
• Effective Date: 01-Oct-2019
• Referred By: ASTM D5722-20 - Standard Practice for Performing Accelerated Outdoor Weathering of Factory-Coated Embossed Hardboard Using Concentrated Natural Sunlight and a Soak-Freeze-Thaw Procedure
• Effective Date: 01-Oct-2019
• Referred By: ASTM D5031/D5031M-13(2018) - Standard Practice for Enclosed Carbon-Arc Exposure Tests of Paint and Related Coatings
• Effective Date: 01-Oct-2019
• Referred By: ASTM D661-93(2019) - Standard Test Method for Evaluating Degree of Cracking of Exterior Paints
• Effective Date: 01-Oct-2019
• Referred By: ASTM D4141/D4141M-22 - Standard Practice for Conducting Black Box and Solar Concentrating Exposures of Coatings
• Effective Date: 01-Oct-2019
• Referred By: ASTM D5146-10(2019) - Standard Guide to Testing Solvent-Borne Architectural Coatings
• Effective Date: 01-Oct-2019
• Referred By: ASTM D6763-16(2022) - Standard Guide for Testing Exterior Wood Stains and Clear Water Repellents
• Effective Date: 01-Oct-2019
• Referred By: ASTM D6577-15(2019) - Standard Guide for Testing Industrial Protective Coatings
• Effective Date: 01-Oct-2019
• Referred By: ASTM D3451-06(2017) - Standard Guide for Testing Coating Powders and Powder Coatings
• Effective Date: 01-Oct-2019
• Referred By: ASTM D1006/D1006M-21 - Standard Practice for Conducting Exterior Exposure Tests of Hand and Factory Applied Paints on Wood and Wood Composite Materials
• Effective Date: 01-Oct-2019
• Referred By: ASTM D4587-23 - Standard Practice for Fluorescent UV-Condensation Exposures of Paint and Related Coatings
• Effective Date: 01-Oct-2019
• Referred By: ASTM D6944-15(2020) - Standard Practice for Determining the Resistance of Cured Coatings to Thermal Cycling
• Effective Date: 01-Oct-2019
• Referred By: ASTM D4082-10(2023) - Standard Test Method for Effects of Gamma Radiation on Coatings for Use in Nuclear Power Plants
• Effective Date: 01-Oct-2019
• Referred By: ASTM G210-13(2023) - Standard Practice for Operating the Severe Wastewater Analysis Testing Apparatus
• Effective Date: 01-Oct-2019
• Referred By: ASTM D3322-23 - Standard Practice for Testing Primers and Primer Surfacers Over Preformed Metal
• Effective Date: 01-Oct-2019

Overview

ASTM D660-93(2019) - Standard Test Method for Evaluating Degree of Checking of Exterior Paints establishes a consistent method for identifying and grading the degree of checking in exterior paint films. Checking is characterized by slight breaks in a paint film that do not penetrate through the last applied coating. Since these surface failures can be difficult to recognize and evaluate, this standard uses clear definitions and illustrated reference standards for comparative assessment. Developed in accordance with internationally recognized principles, ASTM D660-93(2019) helps ensure reliability and comparability of results worldwide, supporting quality evaluation in the paint and coatings industry.

Key Topics

• Checking Definition: Checking refers to the appearance of minor cracks or breaks in the film of exterior paints. This phenomenon does not extend through the most recently applied coating, and can be either visible to the naked eye or detectable under magnification.
• Types of Checking: Several types of checking are recognized within this standard, including:
  • Irregular Pattern: No specific arrangement of breaks.
  • Line and Short Parallel: Breaks are generally parallel short lines.
  • Switch Type: Crossing lines resembling a wire-brushed pattern.
  • Crow Foot Type: Three-pronged cracks forming about 120° angles.
  • Mosaic Type: Geometric, interconnected cracks.
  • Shrinkage Type: Short irregular breaks, often at right angles.
  • Short, Random Type: Isolated short cracks in no specific pattern.
  • Sigmoid Type: Oval-shaped interruptions rarely forming complete circles.
• Use of Illustrated Reference Standards: The standard features visual references for each degree and type of checking, aiding objective evaluations.
• Instructions for Use: The method recommends rating multiple representative portions to account for variable failure patterns, cleaning the paint film gently before evaluation, and recording findings on agreed forms.

Applications

• Quality Assurance in Manufacturing: Paint and coating manufacturers use ASTM D660-93(2019) to ensure products meet durability and weathering resistance standards before distribution.
• Field Evaluations and Maintenance: Facility managers, inspectors, and maintenance teams apply this standard to classify and monitor the extent of film failure on painted exteriors, helping to schedule repairs and prevent more extensive damage.
• Specification Compliance: Contractors and architects reference ASTM D660-93(2019) in project specifications to guide selection and acceptance of exterior paint systems based on standardized failure tolerances.
• Product Development and Research: R&D departments utilize this method to compare performance data of new formulations or treatments under real-world weathering conditions.

Related Standards

• ASTM D714 - Standard Test Method for Evaluating Degree of Blistering of Paints
• ASTM D610 - Standard Test Method for Evaluating Degree of Rusting on Painted Steel Surfaces
• ASTM D661 - Standard Test Method for Evaluating Degree of Cracking of Exterior Paints
• ISO 4628 - Paints and varnishes-Evaluation of degradation of coatings

Practical Value

Employing ASTM D660-93(2019) ensures consistent, objective, and internationally accepted methods for assessing surface failures in exterior paints. By following this standard, organizations can:

• Improve product reliability and longevity
• Reduce maintenance costs by early detection of potential failures
• Establish clear communication regarding coating condition among stakeholders
• Maintain compliance with project documentation and international trade requirements

Keywords: evaluating checking, exterior paints, ASTM D660, paint failure, illustrated reference standards, comparative evaluation, paint coatings durability, paint inspection.

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: D660 − 93 (Reapproved 2019)
Standard Test Method for
Evaluating Degree of Checking of Exterior Paints
This standard is issued under the fixed designation D660; 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.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope 4.1.3 Switch Type—Checking in which the breaks in the
surface of the film form short and long irregular lines crossing
1.1 The illustrated reference standards included in this test
each other in a wire brushed pattern.
method are representative of degrees and types of checking of
4.1.4 Crow Foot Type—Checking in which the breaks in the
exterior paint films. These standards are primarily intended for
surface of the film form in a definite three-pronged pattern with
comparative evaluation.
the breaks running from a center and forming an angle of about
1.2 This international standard was developed in accor-
120° between the prongs.
dance with internationally recognized principles on standard-
4.1.5 Mosaic Type—Checking in which the breaks in the
ization established in the Decision on Principles for the
surface of the film form straight sided, geometric patterns
Development of International Standards, Guides and Recom-
which join on all sides.
mendations issued by the World Trade Organization Technical
4.1.6 Shrinkage Type—Checking in which the breaks in the
Barriers to Trade (TBT) Committee.
surface of the film usually form individual short breaks with
shorter irregular breaks progressing at right angles.
2. Terminology
4.1.7 Short, Random Type—Checking in which breaks in the
2.1 Definitions of Terms Specific to This Standard:
surface of the film form short, irregular patterns. These breaks
2.1.1 checking, n—that phenomenon manifested in paint
are usually individual and do not join.
films by slight breaks in the film that do not penetrate through
4.1.8 Sigmoid Type—Checking in which the breaks in the
the last applied coating.
surface of the film form oval patterns. These oval shapes rarely
2.1.1.1 Discussion—Where precision is necessary in evalu-
complete their circle.
ating a paint film, checking may be described as visible (as
seen with the naked eye) or as microscopic (as observed under 5. Use of Illustrated Reference Standards
a magnification up to ten diameters).
5.1 The use of the reference standards shown in Fig. 1
requires the following precautions:
3. Significance and Use
5.1.1 Since the type and degree of failure may vary over any
3.1 Since checking is not easily recognizable, this test
given area, a representative portion should be rated. It is
method is intended to provide, through definition and
recommended that ratings be made at several locations, noting
illustrations, a means of evaluating the degree of this film
types and degree of failure.
failure.
5.1.2 Care must be taken to recognize that several types of
checking may be present on the same surface.
4. Types of Checking
5.1.3 Paint films may collect excessive quantities of dirt,
4.1 Many types of checking are recognized, of which some
which may mask the type and degree of failure. If necessary,
are:
dirt should be removed by careful and gentle brushing with
...