The most widely-used instrument for evaluating coatings for scratch adhesion and mar resistance is the Balanced Beam Scrape Adhesion & Mar Tester. Originally it was developed at the Bell Telephone Laboratories. It has now been completely redesigned to make it an even more useful instrument.

1. Insure that the weight beam is locked in the raised position. This is done by placing slight inward pressure on the locking pin and raising the weight beam until the locking pin slides into the recess in the cantilever support member. Also insure that the auxiliary table is in place if required by the stylus - panel thickness combination. The Balanced Beam Tester is furnished with an installed auxiliary table. It is secured to the moving table by two pins permanently attached to the auxiliary table. To remove this table lift and forceably wriggle it to disengage the pins.
   
   
2. Secure desired stylus.
   
   
3. Secure the counterweight, place one or more of the weights in the desired position on the weight beam. Each of the large weights is 500 grams and the small weight is 50 grams. To find the gram load on the stylus, multiply the weight value by the hole number on the beam into which the weight or weights have been placed. For example: If the large weight is in the #8 hole and the small weight is in the #3 hole, then (500 x 8) + (50 x 3) or 4000 + 150 = 4150 grams of weight on the stylus.
   
   
4. Withdraw the test panel support table to maximum travel. This action correctly positions the supporting steel balls between the base and the support table.
   
   
5. Place the test panel on the panel support table with one of it edges against the operating bar of the table.
   
   
6. a. Loosen the two locking screws on the pivot.

b. Adjust the jacking screw to raise the pivot block so the test panel can fit under the stylus. With tight downward pressure on the sample, adjust the jacking screw (up or down)until the bubble is in the center of the level.

c. Tighten the two locking screws on the pivot block.

7. With downward pressure on the sample and support table in the area of the stylus, move the assembly to position the test panel as desired under the stylus. This keeps contact with all of the supporting raceway balls and retains them in position, preventing them from all collecting at one end of the base plate.
   
   
8. With the left hand, lift the weight bar to take pressure off the locking pin, withdraw the locking pin to the extent of its travel with the right hand and gently lower the weight bar to bring the stylus into contact with the test panel.
   
   
9. Slowly move the support table with the test panel (0.5 to 1.0 inches per second). If the coating is removed from the panel, continue the testing, using successively higher weights on the stylus until the coating is not removed. If the coating is not removed in the initial test, continue the testing, using successively higher weights on the stylus until the coating is removed from the support panel. Use an untested area of the panel each time the test procedure is repeated.
   
   
10. At the conclusion of the test, raise the weight beam sufficiently to permit the locking pin to secure the assembly in the elevated position. Inspect the stylus to insure that it is clean and has not been damaged in any way. If any defect is noted, the stylus should be replaced. Remove the test panel from the support table.
    
    
11. Record the designation of the material tested, panel surface preparation, coating curing schedule, thickness of the coating, the stylus type and stylus load required to impose failure of the coating and other information pertinent to the particular test.