Test methods usually have a standard form, regardless of which organization developed them.  The sections of a test method include the following.

1. Test number and name – This usually also includes the year that the method was accepted or revised by the organization.

2.  Scope and purpose – This states what types of materials are covered by the test method and for what purpose the method was originally intended.

3. Definition of terms – Any terms that are not generally understood or that have definitions that are specific to the test method is defined.

4. Safety precautions – These are now required for most methods.  They prescribe special handling precautions for chemicals or equipment to be used during performance of the test.

5. Apparatus and materials – This section describes the instruments, devices, and materials that are required to conduct the test.

6. Test specimens – The size, number, and preparation of test specimens are explained.

7. Procedure – This section outlines in detail the steps to follow in performing the test, and any related factors that need to be controlled as the test is performed.

8. Evaluation or calculation of results – This explains how to acquire the data or result.  It includes explanation of any factors, such as ratings or formulas, needed to determine the results.

9. Report – This section indicates what information should be given in the report describing the test results.

10. Precision and bias – The precision to be expected from the test is outlined and may know biases in the test are identified.

11. Notes – Footnotes of additional information, including suppliers of instruments and material, as well as literature reference, are included in this section.

 

Test Criteria: Throughout this text and during your course in textile testing and analysis, you will learn the principles of numerous textile tests that are used to evaluate the performance of textile materials, and you will likely have the opportunity to conduct many of these tests yourself.  You will find that some standard textile test methods are easier that others to understand and interpret, and that some seem to be very applicable to end-use situations, while others do not.  In evaluating a textile material, you may be faced with a choice between two or more test methods that could be used to test a particular performance characteristic.  Textile test methods should meet three criteria, which can also be used when selecting among several standard methods.  These criteria are simplicity, reproducibility, and validity.

Simplicity: The criterion of simplicity means that a textile test method should be easy to read and understand.  It should provide enough information so as to leave no doubt as to how to perform the test, the procedure should be easily mastered with a minimum of practice, and the results should be easily obtained and interpreted.

Reproducibility: The results of a textile test should be reproducible with respect to user, time, and location.  Two individuals who perform the same test on the same specimen should obtain the same results.  Using the same test specimen, you should be able to obtain similar results from one day to the next.  It should be noted that a lack of reproducibility with respect to user to time may be associated with a lack of simplicity.  When a test is difficult to understand or perform or when it involves several steps or extensive handling of specimens, the results may also be difficult to reproduce.

Textile tests should also be reproducible with respect to location.  Using identical specimens, a student working in a laboratory in Athens, Georgia, should obtain the same results as a student performing the same test in Delhi, India, provided that the two students are correctly following the test procedure.

The ideal textile test method specifies how to control factors that could influence reproducibility.  In the wrinkling example presented, we noted the viewing distance, angle, lighting, and other such factors that could influence reproducibility in the determination of SA ratings.  In addition to these factors that are method-specific, environmental factors, (e.g., humidity and temperature) directly influence certain textile properties.  When not carefully controlled, these environmental factors can reduce the reproducibility of textile tests.  These factors are addressed.

 

Validity: The procedure followed in a textile test method should duplicate or closely simulate the actual end-use situation.  In other words, the test method should be applicable to the end use.

In selecting an appropriate test method, the criteria of simplicity, reproducibility, and validity should be considered in conjunction with the goal of a particular test.  For example, there are more sophisticated methods of evaluating fabric wrinkling than our example of SA ratings.  Highly accurate methods exist for counting the number of wrinkles, their depth, and angles. Such procedures can be useful in certain types of research, but for the shirt manufacturer whose goal is to provide a product with a wrinkle-free appearance that will be acceptable to consumers, the use of SA ratings represents a valid, and certainly a simpler approach that can be used in selecting shirting fabrics.

 

All three test criteria are rarely met simultaneously in one textile test.  Sometimes validity is partly compromised in order to achieve reproducibility, as in the case of weathering tests. Instrumental weathering tests cannot actually duplicate exposure to sun and changeable weather conditions, but they do offer reproducibility by allowing the user to control light exposure, temperature, and moisture, factors which would be impossible to control in actual outdoor exposure.  Most instrumental tests also enhance simplicity by providing accelerated conditions, and shorter test cycles than would be possible under real-life conditions.

 

In selecting and conducting any textile test, the basic goal of textile testing and analysis is to aid manufacturers, designers, and merchandisers in providing quality products that meet consumers’ performance expectations.

 

Several validity criterion problems are often associated with standard test methods.  Because they are ‘standard’ (i.e., uniform and controlled), the methods may not actually simulate realistic end-use conditions.  It is usually impossible for a standard test method to simulate the synergistic or antagonistic effects that may occur in actual use.  In the laboratory, we can usually test only one property at a time, for example, strength or abrasion resistance.  However, in actual use, a textile product is subjected to many forces at the same time.  It is difficult to simulate this combination of effects in one standard laboratory test.

 

Further, laboratory tests are continuous, and usually accelerated, whereas actual wear is intermittent and characterized by low degree of stress.  This makes it difficult to simulate wear in a single laboratory test.  For example, fabric abrasion over the life of a shirt may be due to a combination of bending and rubbing at the elbows, occasional low-stress rubbing against the fabric of a jacket worn over the shirt, gradual abrasion at the cuffs and collar, and contact with other fabrics and surfaces during laundering; however, most laboratory tests are not designed to simulate all of these components of the abrasion process.  Lastly, because people are different, they will subject products to different kinds and degrees of wear, and will care for them differently.  These factors present further problems in testing for performance in end-use conditions.

 

In testing, the term, validity may imply that a valid test gives the true value of a property.  However, this is rarely the case. Most textile tests do not purport to give the absolute or true value of a property; rather, they are most often used to compare the performance of different products.