Drawdown card
From Wikipedia, the free encyclopedia
Drawdown cards are used for testing paints and coatings through wet film preparation. Reliable and accurate testing of coatings and films such as those in the paint and coatings industry, requires rigid control of their actual (not assumed) wet and dry film thickness. Hiding power, opaqueness, scrub resistance, and many other quality tests require a uniform, repeatable film for routine quality control and research and development testing. Many ASTM, ISO, Federal, and other specifications specify films of predetermined and uniform thickness.
The most common method of spreading a sample is with a film applicator, also called a drawdown bar or doctor blade. A typical blade type applicator consists of a metal bar containing a gap of known depth or clearance on one or more faces. It is then placed at one end of the drawdown card and a sufficient volume of sample is placed in front of the applicator. The applicator is then "drawn down" the chart, leaving a uniform film behind it. The card is available in different black and white patterns for different applications and tests.
