Mexico. The Ministry of Economy, through the General Directorate of Standards, issued the declaration of validity of the Mexican Standard NMX-U-118-SCFI-2013, of coatings, paints, varnishes and related products-test methods to determine the covering power and the contrast ratio of paints and coatings by reflectrometry.
The standard that was developed and approved by the Technical Committee for National Standardization of Paints, Varnishes, Coatings and Inks for Printing (Cotennarec) is aimed at producers, distributors, consumers and the general public related to the sector.
The following are some objectives and fields of application:
- Determine the contrast or opacity ratio of water-based or solvent-based paints and coatings, at a specific thickness, by measuring their reflectance on a white and a black substrate.
- Determine the covering power by reflectometry of water-based or solvent-based paints and coatings, using the tristimular values of "Y" and the Kubelka-Munk equations; without a reference material.
- The two procedures of this Mexican standard apply to both water-based and solvent-based coatings and paints that dry into the air. They can also be used to evaluate chemically curing finishes, applying appropriate modifications.
- Procedure A applies to paints and coatings of any color, only the appropriate thickness for each color should be specified.
- Procedure B applies to paints and coatings of white and light colors; however, very approximate results can be obtained for color paints, with tristimular values of "Y" greater than 15%.
The full text can be obtained from the electronic catalogue of the Directorate-General for Standards: http://www.economia-nmx.gob.mx/normasmx/index.nmx
