AATCC 183-2020 Test Method for Transmittance or Blocking of Erythemally Weighted Ultraviolet Radiation through Fabrics.
8. Instrument Verification and Calibration
8.1 Calibration. Calibrate the spectro- photometer or spectroradiometer according to manufacturer instructions. The use of physical standards is recommended for validating the measurement of spectral transmittance.
8.1.1 When running a wet sample place the plastic wrap over the port and repeat calibration.
8.2 Wavelength scale. Calibrate the wavelength scale of the spectrophotometer or spectroradiometer using the spectral emission lines of an electrical discharge in mercury vapor. The wavelength calibration of a spectrophotometer can be performed using the absorption spectra of a holmium oxide glass filter. Reference wavelengths for both mercury arc emission and holmium oxide absorption are provided in ASTM E275.
8.2.1 Transmittance scale. Set the transmittance scale to a 100% value by operating the instrument without a sample in the optical path; therefore, referenced to air. The 0% value can be subse- quently verified by fully obstructing the sample beam path with an opaque material. Validate the linearity of the transmittance scale by means of either calibrated neutral density filters or calibrated perfo- rated screens supplied by the instrument manufacturer or standardizing laboratories.
8.3 Verification checks on the operation of the test and the apparatus should be made and kept in a log. The use of a verification fabric is recommended at least once a month unless no testing is to be performed that month.
9. Specimens
9.1 Test a minimum of two (2) speci- mens from each sample, one each for the wet and the dry testing. Cut each specimen at least 50 × 50 mm (2.0 × 2.0 in.) or 50 mm (2.0 in.) in diameter. Avoid dis- torting the specimen during preparation and handling.
9.1.1 Should the fabric have areas of different colors or structure, test each color or structure if its size is sufficient to cover the measuring port.
9.2 See Appendix A5 for specimens exhibiting fluorescence.
10. Conditioning
10.1 For dry specimens, bring to mois- ture equilibrium in a standard atmosphere according to ASTM D1776. Use conditions listed for Textiles, General in Table I of the standard.
11. Procedure
11.1 Dry Evaluation.
11.1.1 Place the specimen flush against the sample transmission port opening in the sphere.
11.1.2 Make one UV transmission measurement with the specimen oriented in one direction, a second measurement at 0.79 rad (45°) to the first and a third at 0.79 rad (45°) to the second. Record the individual measurements.
11.1.3 On multicolored specimens, de- termine the area of highest UV transmis- sion and make the three measurements at 0.79-rad (45°) rotation intervals in that area.
11.2 Wet Evaluation
11.2.1 Weigh the test specimen. Thor- oughly wet out the specimen in distilled water by placing it flat in the bottom of a beaker and then pour distilled water into the beaker until the specimen is covered. Allow the specimen to remain submerged for 30 minutes. Press and move the specimen from time to time to ensure a good and uniform penetration. Prepare only one specimen at a time. 11.2.2 Bring the wet pickup to 140 ± 5% by squeezing the wet specimen be- tween blotting paper through a hand wringer or similar convenient means (such as squeezing between two glass rods). If the fabric has low moisture absorption, repeat the soaking and wringing steps. Note, some samples may not be capable of achieving the specified wet pick- up such as tightly woven synthetic fabrics.AATCC 183 pdf download.