Dr. Buckel explained he had had numerous contacts with Taber Industries, which clarified that the last Round Robin test for the Taber test was performed in 2004, while last wheel types were delivered in 2008. Dr. Buckel was of the opinion that, according to the results of the round robin, the main influencing factors seem to be the nozzle gap and the wheel lot (tests performed with wheels coming from different wheel lots may provide different results).

The informal group held a telephone meeting with Taber Industries (TI):

The experts firstly discussed documents IGPG-03-06 (tracking card) and IGPG-03-05 (comments from TI about the round robin):

• - As all equipments passed the test, it was proposed to pay attention primarily to the ones on the “borderline”.
• - Lab 2: could be the flatness of the table, misalignment of the arm, age of the instrument (1989, bearing not replaced).
• - Lab 3: 11 year old instrument, arm alignment. Arm re-alignement can be performed by Ericsson (EU) as having good relations with Taber.
• - Lab 4, Lab 5: OK
• - Lab 6: Test 1, 1-5 O’clock: OK, 6-9 o’clock quite deviated.
• - Lab 7: TI definitely recommended improving the toe.
• - About lab 9, there was no recommendation TI could provide.

Nozzle distance: document IGPG-03-09, the table of percentage light demonstrates the influence of the nozzle distance. TI made some tests showing a clear influence of the nozzle distance on the haze values recommended 0,8 mm as the correct value.

Lab 9 used wheels from 2 different lots. TI committed to investigate the difference between the lots DY22 and DW22.

Test data verification of MPA (IGPG-03-04):

Dr. Dümmler questioned how TI would avoid future problems like that described in document IGPG-03-04. TI said they contacted their supplier, identified the root cause of the issue, dealing with the raw material. TI added additional tests on the raw materials and indicated that they are produced overseas, yet the suppliers are in the USA, making the contacts relatively easy. Other wheels of that lot, manufactured 3 years ago, were also investigated, not showing any problem. Traceability of the raw material is well maintained by TI. TI had indeed no feedback about labs using the wheels for plastic glazing.

It was questioned whether TI provides recommendations for which material the Taber test is recommended (scope of the test) i.e. is there any restriction for certain materials.

TI clarified that CS10F is relevant for haze on coating material. But certainly not for e.g. acrylic or plastic, uncoated, with 1000 cycles. Not only is the material different (physics), but the preparation of the samples as well. TI also pointed out that different wheels can address different materials. TI did not expect the type of ranges the informal group encountered and hence committed to further investigate the issue.

It was questioned how can a lab verify the wheels before testing, instead of waiting for inappropriate results.

TI recommended to test the wheels with a material whose expected results are known (method used by TI). TI has a large bank of reference material. When questioned about an example of a reference material, TI suggested as a recommendation simply using a material with known results.

The informal group however could not accept such recommendation as the order of results with the 3 different materials is not consistent (the results for the three materials have no correlation). TI committed to further investigate this point.

Document IGPG-03-07:

TI confirmed they use a brush to reface the wheels after testing. TI confirmed that this could generate static electricity and that distance, state and cleanness of the nozzle are of high importance. The Taber test is sensitive and all details must be well calibrated. TI recommended abrading right away after cleaning.

Conclusion:

• - TI welcomed any comment by email.
• - Most influencing parameters were investigated.
• - TI did not provide any indication of what material could be used as a reference, seeing the discrepancies between PC and PMMA. Dr. Dümmler and Mr. Helmich recommended continuing investigating the Taber test, at least up to the time ISO finishes its work.

A debate took place about the work ISO is currently conducting. Dr. Dümmler recalled that ISO is looking to clarify the standard for permitting any wheel supplier (Taber, Daiwa), i.e. finding a relevant abrasion (wheel) technical specification. The difficulty is to assess the wheels w/o destructing them. Yet the experts agreed that adding a new wheel supplier could add a new parameter (Taber wheel, Daiwa wheel, equipment).