Coating chalking tester Model 241

comparisondurabilityfor paint

Technical description
The first visible sign of weather-induced degradation of a paint coating is the loosening of pigment particles at the film surface, a phenomenon known as "chalking". Loose pigment can be removed by light wiping and indicates the start of film decomposition and reduced service life.

Self-cleansing paints
Some modern coatings are formulated to allow controlled chalking so that contaminants are washed away by rain, renewing the surface and maintaining colour durability and cleanliness without reducing life expectancy.

Purpose and application
The quantitative determination of chalking rate is essential for:

• Selecting suitable raw materials for a given application
• Determining optimum pigment volume concentration with regard to weather resistance or self-cleansing properties
• Evaluating natural and accelerated weathering tests
• Comparative assessment of raw materials and competitor products
• Defining maximum warrantable periods for large-scale contracts

Principle
Loose pigment particles at the film surface (due to binder decay) are pressed into the swollen gelatin layer of photographic paper under a specified pressure (standard 250 N). The pigment imprint in the photographic paper is then visually compared to a chalking scale or a comparison paint according to the selected evaluation method.

Design and operation
The Kempf Chalking Rate Tester, Model 241, is a light-alloy cylinder fitted with a 40 mm diameter rubber stamp (Shore A hardness 60 ± 5). An integral spring provides an adjustable stamping force from 50 to 250 N. Ring markings on the stamp shaft at 50 N intervals enable using lower forces than the standard 250 N. For consistent vertical pressure over the stamp area, use of the optional special stand is recommended.

Scope of delivery

• Chalking Rate Tester Kempf Model 241
• Chalking scale

Standards

• DIN 53 159

Accessories (examples)
Special stand (accessory), pressure springs, spare rubber stamps, Manufacturer's Test Certificate M (factory calibration).

Technical specifications

• Drive: Manual
• Testing force: up to 250 N (adjustable 50–250 N)
• Stamp diameter: 40 mm
• Stamp hardness: Shore A 60 ± 5
• Tester dimensions: Height 270 mm // Ø 50 mm
• Tester net weight: approx. 1.2 kg
• Special stand dimensions: H approx. 450 mm // W approx. 150 mm // D approx. 250 mm
• Special stand net weight: approx. 5.5 kg