What is ISO 7783 about?
ISO 7783 discusses paints and varnishes. Water vapor transmission is a measure of the passage of water vapor through a substance. It is a measure of the permeability of vapor barriers. It generally decreases with the increasing thickness of the film/barrier and increases with increasing temperature.
ISO 7783 specifies a method for determining the water-vapour transmission properties of coatings of paints, varnishes, and related products. It supplements ISO 12572. As far as possible, the procedure, the definitions, and the calculations have been taken over from ISO 12572.
Note: Water-vapour transmission rates of more than 680 g/(m2â‹…d) (i.e., water-vapour diffusion-equivalent air layer thicknesses, sd, of less than 0,03 m) are not accurately quantified by the test method described in ISO 7783.
Who is ISO 7783 for?
ISO 7783 on paints and varnishes (determination of water-vapor transmission properties) is useful for:
- Paint manufacturers
- Quality control personnel
- Painters
Why should you use ISO 7783?
The water-vapour transmission rate is not necessarily a linear function of film thickness, temperature, or relative-humidity difference. A determination carried out under one set of conditions will not necessarily be comparable with one carried out under other conditions. Therefore, it is essential that the conditions of the test are chosen to be as close as possible to the conditions of use.
ISO 7783 is one of a series of standards dealing with the sampling and testing of paints, varnishes, and related products. ISO 7783 describes a method for determining the water-vapour transmission rate of self-supporting and non-self-supporting coatings.
Water-vapour transmission is of greatest interest under conditions of high humidity. For this reason, the wet-cup method has been adopted as the reference method.
What’s changed since the last update?
BS EN ISO 7783:2018 supersedes BS EN ISO 7783:2011, which is withdrawn. BS EN ISO 7783:2018 includes a technical change with respect to BS EN ISO 7783:2011:
- Correct the conversion factor in Formula (3) and add a reference to ISO 4618 on paints and varnishes terminology in Clause 3.
