Calcium Chloride Method / Potassium Acetate Method
The Calcium Chloride Method / Potassium Acetate Method is a test method that uses a desiccant or saline solution to measure the amount of water vapor passing through fabric and evaluate moisture permeability.
Contents6 sections
Definition and Overview
The calcium chloride method and potassium acetate method are test methods that quantify moisture permeability related to stuffiness inside clothing under fixed conditions. A specimen is attached to a container, and the amount of water vapor movement caused by the difference in water vapor pressure inside and outside the container is measured.
In the calcium chloride method, the calcium chloride inside the container absorbs water vapor. In the potassium acetate method, an aqueous potassium acetate solution is used to create humidity conditions, and the amount of water vapor passing through the specimen is evaluated.
Characteristics of the Evaluation Value
The measurement result is generally treated as moisture permeability, and a higher value indicates that water vapor passes through more easily under the test conditions. However, values obtained with different test methods, temperatures and humidity levels, test times, and specimen conditions cannot be compared simply.
Moisture permeability is an index that shows the function of fabric alone or laminated materials, and it does not directly evaluate texture, thickness, or appearance. Even with the same moisture permeability, the feeling of stuffiness during wear varies depending on the material, weave, coating or membrane, and whether there is a lining.
Main Applications
It is used for development and quality verification of materials that should suppress water penetration while allowing water vapor inside clothing to escape, such as waterproof breathable materials, coated fabric, and laminated fabric. It is often used to check outerwear, rainwear, sportswear, and outdoor wear.
It is also useful as a reference when considering comfort during perspiration in lightweight spring and summer clothing and uniforms. However, since air permeability, water absorption, moisture absorption, and skin release also affect wearing comfort, it is important not to judge suitability for applications based on moisture permeability alone.
Selection and Handling Notes
When selecting fabric, confirm not only the moisture permeability value but also the test method and test conditions used. For products that require waterproofing, also confirm water pressure resistance; for products that emphasize resistance to stuffiness, also check air permeability, and evaluate according to the product specifications.
This test does not directly indicate shrinkage, wash durability, or ease of sewing. When changes in function due to washing or abrasion are anticipated, check the test results after washing and the durability of the processing. In products, seams, zippers, and linings also affect the movement of water vapor.
Differences from Similar Terms
Moisture permeability is a performance value that indicates how easily water vapor passes through, and the calcium chloride method and potassium acetate method are test methods used to measure that value. Waterproof breathable refers to materials or functions that combine waterproofing, which suppresses water penetration, and moisture permeability, which allows water vapor to pass through.
Air permeability is a property that evaluates how easily air passes through and differs from moisture permeability, which evaluates the movement of water vapor. Even materials with low air permeability may allow water vapor to pass through depending on their structure and membrane properties.
Frequently Asked Questions
Can the values of the calcium chloride method and potassium acetate method be compared?
Basically, compare values obtained with the same test method, test conditions, and specimen condition. Since the humidity conditions created inside the container and the measurement concept differ between the two methods, it is not appropriate to compare the moisture permeability values of different test methods on the same basis.
If moisture permeability is high, will it always feel cool?
Not necessarily. Coolness and stuffiness are also affected by air permeability, water absorption, moisture absorption, cool to the touch, the looseness inside the clothing, and the structure of the lining or layering. Evaluate with multiple test values and actual wear tests according to the application.
