This is a threaded stainless steel rod that functions as a grooved doctor blade at any part of its circumference. It produces a film with parallel ridges and valleys in simulation of brush marks. Advantages over brushout application tests are speed, reproducibility, and a regular surface pattern. The leveling of films applied in this manner correlates well with brushout leveling, thereby providing a reliable means for evaluating this property
The LTB-2 has alternating clearances of 300 and 100 µm (12 and 4 mils), to apply alternate stripes of 150 and 50 µm (6 and 2 mils) thickness. Thus the mean wet film thickness of the test drawdown will be about 100 µm (4 mils), corresponding to a spreading rate of 10 m²/L (400 ft²/gal).
The companion product for the LTB-2, LS-2 Drawdown Levelness Standards, is discontinued. These were 3-dimensional plastic replicas of drawdowns made with the LTB-2, ranging from extremely poor to good leveling. However, due to the unavailability of the material used to produce this item, we can no longer make it. We will be proposing to ASTM Subcommittee D01.42 Modifications to the existing standard, ASTM D 4062-11, which allow for the comparison of drawdowns made with the LTB-2 against retained or historical samples instead of the LS-2 plastic standards.