Leneta Instruments

No. LTB-2
Used in ASTM D4062 Test method for "Leveling of Paints by Drawdown Method" - This is a threaded 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. Critical dimensions are indicated in Fig. 2. Plastic arms, in conjunction with straightedge guides, assure rectilinear movement of the blade. Test advantages compared with brushout application are speed, reproducibility, and a regular surface pattern that facilitates evaluation. It has been demonstrated that the leveling of films prepared in this manner correlates very well with brushout leveling.

The diagram shows alternate clearances, in equal width, of 300 and 100 μm (12 and 4 mils). Since the wet film thickness laid down by a doctor blade is about half its clearance, it can be expected that the Leneta Leveling Test Blade will apply alternate stripes about 150 and 50 μm (6 and 2 mils) thick. Thus the amplitude of the square wave formed at the instant of application will be approximately 50 μm (2 mils) and the approximate average wet film thickness will be 100μm (4 mils). The latter value multiplied by the nonvolatile fraction by volume, gives the equivalent dry film thickness. See instructions in this section.

General Description: A glass clipboard is set firmly on a phenolic plastic panel and the whole apparatus is mounted on rubber bumpers to prevent sliding while in use. The drawdown surface is 6mm (1/4 inch) thick polished glass, equal in planarity to fine mirror glass. A steel clip holds the test chart or panel steady while the drawdown is made. These devices provide economical and convenient means for making drawdowns of uniform film thickness. In some cases they are superior to vacuum plates. They are easy to use, easy to keep clean, and will be found extremely helpful in every paint and coatings laboratory.

1. Rotary power mixer, capable of 1300 and/or 3600 rpm
2. Mixing can–Pint (500 mL) conventional paint can
3. Mixing can–175 mL

1. Stir coating thoroughly with a spatula. Strain if necessary.
2. Fill the mixing can approximately half.
3. Attach the mixing paddle to the rotary power mixer.
4. Set speed at 1300 rpm for the 175 mL can or 3600 rpm for the 500 mL (pint) can.
5. Position paddle about 1/4 inches (6mm) from bottom of can.
6. Mix 1 minute then promptly place about 8 mL of paint in front of the drawdown blade.

1. The Leneta Anti-Sag Meter.
2. The Leneta Adjustable Straight Edge.
3. The Leneta Drawdown Plate–Regular.
4. Drawdown Charts* Form 7B, black and white; for light colored paints. Form WB, plain white, for dark colored paints.
5. Catch-Papers, Form CP-1.
6. Pre-shear equipment.
   *With the Low Range Anti-Sag Meter use glass or flat metal panels.

1. Stir thoroughly and adjust to 23°C (73.5°).
2. Pre-shear in accordance with one of the methods furnished and test immediately thereafter.

1. Attach the straight-edge onto the drawdown plate in suitable position.
2. Place a test
   chart on the drawdown plate under the clip.
3. Place Anti-Sag Meter on the chart, with it's
   open side toward operator and it's shoulder against the straight edge.
4. Position Catch-Paper
5. Place a suitable quantity (8-10mL) of pre-sheared paint directly in front of the
   blade and draw down uniformly at about 6" (150mm) per second.
6. Promptly fasten the drawdown chart to a vertical surface, with stripes horizontal and left edge (thinnest stripe) at the top, and allow to dry in that position.

1. Note the notch numbers marked on the Anti-Sag Meter and Identify the corresponding
   stripes accordingly.
2. Ignore the leading and trailing edges, and observe only the central 5-1/2" (140 mm) of blade path corresponding to the black area of Form 7B.
3. The lowest (thickest) stripe that does not touch the one below itself is referred to as the index stripe, and its notch number is the Anti-Sag Index of the paint.
4. For more precise Anti-Sag Index, add to the Index stripe number the product of the post-index clearance step and a fractional degree to which it has failed to merge with the next lower stripe. The fraction is estimated in accordance with the following table:

Leneta Magnetic Spray Stand, No.SS-1,
showing a 6" x 12" steel panel in position
for spraying.