ASTM D1640 Standard Test Methods for Drying, Curing, or Film Formation of Organic Coatings
What is ASTM D1640/D1640M?
ASTM D1640/D1640M is a set of standard test methods for the stages and rates of drying, curing, and film formation of organic coatings. The methods are performed under laboratory-controlled conditions of air temperature (low, ambient, or elevated) and humidity. The standard also describes procedures for assessing drying under shop and field conditions. Therefore, laboratories can compare coatings and how changes in composition affect drying time. In addition, the test methods apply to coatings on smooth, non-absorbent substrates. The standard treats SI units and inch-pound units as separate standards. As a result, users must not combine values from the two systems.
Get Certified ASTM D1640 for Coating Performance Assurance
ASTM D1640 testing helps determine how fast an organic coating dries, cures, and forms a film. As a result, manufacturers can compare coatings and see how formulation changes affect drying time. Moreover, the shop and field procedures help assess drying time under actual conditions. Experienced analysts follow the standard and report clear results. Therefore, users can make confident decisions about coating performance.
What is the Scope of ASTM D1640/D1640M Testing?
ASTM D1640/D1640M standard test methods cover determining the stages and rates of film formation during the drying or curing of organic coatings. They apply under laboratory-controlled conditions and under shop and field conditions. Specifically, the scope includes the following points.
Material type: Organic coatings, such as paints, applied to smooth, non-absorbent substrates. The coating is the material under test. The methods do not reflect absorption of the coating vehicle into the substrate.
Purpose: Determining the stages and rates of drying, curing, and film formation. Users compare coating types and assess the impact of composition changes on drying time. The methods also assess drying and curing time in the shop or field.
Property evaluated: The drying, curing, and film formation of the coating over time. ASTM uses the terms dry, cure, and film formation interchangeably. The test follows how these stages progress under set conditions.
Method: Test Methods A, B, and C cover different temperature and humidity conditions. Method B evaluates cooler temperatures and low-temperature curing agents, catalysts, or accelerators. Method C evaluates elevated temperature and relative humidity.
Typical test surface: A smooth, non-absorbent substrate. ASTM limits Methods A, B, and C to coatings applied to such substrates. ASTM refers to Practice D823 for producing films of uniform thickness on test panels.
Limitations: Methods A, B, and C compare coatings only on smooth, non-absorbent substrates, so they do not show absorption into the substrate. SI units and inch-pound units are separate standards, and users must not combine them. The standard does not address every safety concern, so users set their own safety, health, and environmental practices.
Applications: Comparing types of coatings and developing coatings for various uses. Assessing how compositional changes affect drying time. Assessing drying and curing time in the shop or field.
What are the Uses of ASTM D1640 Testing?
These test methods give laboratories and manufacturers a standard way to track how a coating dries and cures. ASTM provides three methods for different temperature and humidity conditions. Therefore, the standard supports several practical uses. The main uses include the following.
Determines the stages and rates of drying, curing, and film formation
Compares different types of coatings
Assesses how compositional changes affect drying time
Assesses drying and curing time in the shop or field
Evaluates the effect of cooler temperatures on drying rates with Method B
Evaluates low-temperature curing agents, catalysts, and accelerators with Method B
Evaluates the effect of elevated temperature and relative humidity with Method C
Why is ASTM D1640 Important?
A coating must dry and cure properly to form a usable film, and low temperature can slow drying significantly. Elevated humidity can speed up drying for some coatings and harm others. These test methods give a consistent way to measure the stages and rates under defined conditions. Therefore, manufacturers can compare coatings and assess how changes in composition affect drying time. In addition, the shop and field procedures help assess drying under actual conditions.
ASTM D1640/D1640M Equipment and Sample Preparation Guide
Drying tests need a coated panel, a controlled environment, and a way to apply the film evenly. The substrate must be smooth and non-absorbent, so the test reflects the coating itself. The table below summarizes the sample, preparation, dimension, and equipment details. It also shows what the technician and analyst do at each point.
The sample is an organic coating, such as a paint, applied to a smooth, non-absorbent substrate. The coating and the substrate together form the test specimen. ASTM limits Methods A, B, and C to this type of substrate.
Specimen Preparation
The technician applies the coating as a uniform film on the test panel. The technician then places the panel under the selected temperature and humidity conditions.
Specimen Dimensions
The technician measures and records the film thickness for each panel.
Instrumentation
The tests need conditions that control air temperature and humidity, which can be low, ambient, or elevated. The analyst checks and records the conditions throughout the test.
What Are the ASTM D1640/D1640M Testing Procedure and Requirements?
The procedure moves from method selection to result reporting. Each step affects how well the test reflects the drying of the coating. The exact conditions are in the full standard. The table below lists the major steps in order.
ASTM provides Methods A, B, and C. Method B covers cooler temperatures, and Method C covers elevated temperatures and relative humidity. The analyst selects the method that matches the conditions of interest.
Panel preparation
The technician prepares a smooth, non-absorbent panel and applies the coating as a uniform film. The technician measures the film thickness.
Conditioning
The technician places the coated panel under the chosen air temperature and humidity. For shop and field assessments, the panel stays under the prevailing conditions.
Drying assessment
The analyst checks the film at intervals to follow the stages of drying, curing, and film formation. The analyst records the time at which each stage occurs.
Result reporting
The laboratory reports the stages and rates of film formation together with the test conditions. The report also names the method used.
ASTM D1640/D1640M Testing Process and Data Collection
A technician first prepares a smooth, non-absorbent panel and applies the coating as a uniform film. The technician then places the panel under the selected temperature and humidity conditions. Next, the analyst checks the film at intervals to follow the drying stages. The analyst records each observation with the elapsed time and the conditions. Finally, the laboratory reports the stages and rates of film formation. Therefore, data collection centers on the time to each drying stage and the conditions during the test.
ASTM D1640 A coated test panel drying in a controlled environment.
Common Challenges and Troubleshooting
Environmental control is the main challenge. ASTM states that low temperature can slow drying, and some coatings dry faster or slower at elevated temperatures and humidity. As a result, small changes in conditions can change the drying time.
To troubleshoot, technicians keep temperature and humidity at the selected values and record them. In addition, they use uniform films on smooth, non-absorbent panels, since absorption into the substrate affects drying. Moreover, they compare coatings only under the same method and conditions. Users also set their own safety practices, since the standard does not address every safety concern.
ASTM D1640/D1640M Analysis Results and Interpretation
The test results describe how quickly each stage of drying, curing, and film formation occurs in an organic coating. These stages help manufacturers evaluate coating behavior under different environmental conditions.
Analysts compare coatings only when they are tested using the same method, temperature, and humidity to ensure consistent results.
Method B evaluates the effects of lower temperatures and low-temperature curing agents on the drying and curing process.
Method C evaluates the effects of elevated temperature and relative humidity on coating performance.
Methods A, B, and C assess coatings on smooth, non-absorbent substrates. Therefore, the results do not account for coating absorption into the substrate.
Shop and field test results apply only to the environmental conditions present during testing.
It measures the stages and rates of drying, curing, and film formation of organic coatings. It works under laboratory-controlled conditions and under shop and field conditions.
What are Methods A, B, and C?
ASTM provides three methods for different temperature and humidity conditions. Method B evaluates cooler temperatures, and Method C evaluates elevated temperature and relative humidity.
What substrates does the method cover?
Methods A, B, and C compare coatings on smooth, non-absorbent substrates. They do not reflect absorption of the coating into the substrate.
How much does drying time testing cost?
The cost depends on the number of coatings, the method, and the reporting needs. Please request a quote.
How long does testing take?
Turnaround depends on the number of coatings, the drying time, and the laboratory schedule. Please request a timeline.
Zunaira Tehseen is a scientific content specialist who bridges interdisciplinary research across biochemistry, molecular genetics, and materials science with technical content management. Leveraging expertise in bio-interface characterization, advanced materials evaluation, and AI-driven workflows, she curates, structures, and communicates complex technical data. At Matestlab, she leads content strategy and documentation for metallographic testing, mechanical characterization, and compliance with international standards such as ASTM and ISO, delivering precise, high-impact technical assets for industrial and scientific audiences. Know More
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