This practical instrument measures accurately the hiding power of paints, in relation to their thickness.
A small quantity of product is laid down on a flat opaque glass plate, black or white depending on the model, bearing a scale graduated from 0 to 50 mm.
A second transparent glass (or cursor), fitted with two very short studs, traps the film in a corner shape.
The cursor is moved forwards and backwards, and it is observed from which graduation the film fully covers the background.
Pfund cryptomer can gives estimate of coverage in square meters per liter anf is very suitable for uwe with coatings containing pigments
The Pfund cryptometer consists of a glass plate, half black half white as the base.
Each half of this base has a scale engraved from 0-50 mm along one ede starting from the division in the center.
Two glass top plates are included with each instrument and these have two metal supports at one end so that these transparent top plates rest at an angle when placed upon the black and white area of the base plate.
The top plates differ in the length of their tiny supports so that different angles are formed between the top plates and the base plate.
A wedge angle constant(K)is given to each top plate.
These range from the smallest angle K=0.002 to K= 0.0035, K= 0.004, K= 0.007 and the largest K=0 .008, the popular constants being K=0.004 and K=0.008.
Reflectance of white part 80±2
Reflectance of black part ≤2
Weight 1.0 Kg
Dimensions 100mm×170mm×20mm. (L×W×H)
The appropriate top plate for the paint to be tested is selected, usually K=.008 for light coloured paints and K= .004 for dark coloured paints. (Alternatively, K= 0.002 for higher opacity coatings and K= 0.007 for less opaque coatings).
A blob of paint, typically 3-5 ml is placed in the center of the base plate close to the black/white division.
For light colours, the top plate (e.g. K= .008) is placed over the paint with the supports on the white area of the tile.
The top plate is pressed down firmly so that the paint is spread without air bubbles to form a shallow wedge between the plates.
This wedge will move with the top plate, the position of which is adjusted until the moment that the black/white division disappears.
The scale reading is then noted from the black scale where the edge of the top plate makes contact with the base plate.
When testing a dark coloured paint the top plate (e.g. K= .004) is used and the scale reading taken on the white area.
The thickness of paint in millimeters over the black and white division is obtained by multiplying the scale reading times the wedge constant K of the top plate used.
This figure records the minimum film thickness necessary to obscure the black and white.
The coverage or spreading power for this thickness can be obtained directly from the conversion tables below for each of the top plates.
298-4500/35K----- Glass Plate(K=0.0035)
298-4500/40K----- Glass Plate(K=0.004)
298-4500/70K----- Glass Plate(K=0.007)
298-4500/80K----- Glass Plate(K=0.008)