The physical characteristics of cotton are mainly influenced by their moisture content and the air conditioning mode applied to the samples too, which must be brought to a moisture content in equilibrium with the stable environmental conditions of the laboratory and approved before and during the tests running according to the Standard.
For the air conditioning and for test analyses on cotton the reference Standard is the ASTM D-1776, "Standard Practice for Conditioning and Testing Textiles. For cotton testing" that fixes thermo-hygrometric reference values at:
- Temperature: 21 ± 1°C (70 ± 2°F);
- Relative humidity: 65 ± 2%
The permitted tolerances for R.H. are fixed at ± 2% and this is the most relevant goal, which isn't only achieving the value of the 65% of R.H., but particularly keeping it inside the limits; it is possible to add compensations for slight variations on the absolute value of humidity, if the reading value of R.H. remains constant, for example, at 62% or at 63%, but definetely it cannot be applied any compensations on continuous fluctuations of Relative humidity.
The laboratory must be conditioned to reference thermo-hygrometric parameters for 24/24 hours, 7/7 days during the entire Cotton season and when tests are carried out.
It's important that the climatic conditions in the laboratory just are kept inside tolerances, alternatively all test running with HVI equipments must cease immediately and the environmental conditions must be reached again.
It is necessary to check and record the values of temperature and humidity continuously with probes independent from those of the regulation. In addition, the sensors of the probes need to be calibrated periodically by technicians with a certified instrument as for example a certified psychrometer.
For the test on cotton fiber it is possible to calculate an average value for the records stored for a maximum period of 5 to 10 minutes. The aim is to avoid variations responsible for most of the errors of measurement on cotton fiber as well as drifts over periods of long duration.
In order to keep the laboratory conditions in the allowed ranges the optimization of laboratory construction is necessary to avoid the influence of disturbing elements as heat, radiation, solar radiations and fumes coming from the external environments and minimizing their impact through efficient thermal insulation of the walls and ceiling.
The technical team S.T.A. Branca Idealair, thanks to the contribution of the technical department for Laboratory Project Development for HVI COTTON ANALYSES, provides the installation and sealing of the walls, the insulated ceiling and of the false ceiling for the air in distribution, providing the correct sizing of the Climatic Element Branca Idealair to ensure the best close-control regulation on thermo-hygrometric parameters.
For samples relatively wet or dry, S.T.A. Branca Idealair include in the draft a pre-conditioning chamber realized for the samples set on the dry side without the use of driers and heaters. The relative humidity inside the pre-chamber will be maintained at constant values closed to those required inside the laboratory, but with wider tolerances as requested by ASTM D5867.