Current Information on Reported Issues on Tint Testing

Numerous industry laboratories have reported to ASTM Committee D24 on Carbon Black that they have encountered issues while performing the tint test (D3265). The issues appear to be related to the use of specific lots of Paraplex G-62 oil and/or zinc oxide used in the preparation of the tint pastes. These issues have been reported to result in measurement bias and/or difficulty with paste preparation. The D24.21 subcommittee has confirmed these issues are valid and can cause test bias as large as 10 units or more. The subcommittee is actively working with a task group to resolve these issues.

The task group met on November 11, 2015 and made the following decisions:

•Balentine Enterprises purchased an estimated 5 year stock of zinc oxide from Zinc Oxide LLC, lot 5099. This material is designated as ASTM Lot 11; and it provided the closest match to ASTM lot 8 with several standard grades of carbon black.

NOTE - Some labs reported significant differences in Tint Strength of specialty blacks for lot 11 compared with lot 8. Although significant differences were observed for specialty grades only it will be reviewed if some Tint Strength specification changes may be needed for grades defined in ASTM D1765. This information will be obtained overtime and reflected in the standard on a case-by-case basis.

•Balentine Enterprises purchased an estimated 10 year stock of Epoxidized Soybean Oil (ESO) from GreenChem Industries LLC. This material provided equivalent data as HallStarParaplex G-62 materials produced prior to 2012.

•The D24.21 task group will initiate a new ITP program to retest the Industry Tint Reference Black (1 & 2) and ASTM Standard Reference Blacks (SRB series-8). The new precision data (r & R) will be published as soon as possible.

Until new precision statistics have been generated with the SRB series-8, ITRB/ITRB2, and the above new raw materials, any discrepancies with tint strength arising between suppliers and users of carbon black should base referee testing on the following raw materials:

•Paraplex G-62 produced prior to June 2012

•ASTM Zinc Oxide Lot 8

When tint testing discrepancies are observed and confirmed within a laboratory, and the raw materials identified above are not available for use, tint testing within that lab is considered unreliable.

The committee encourages anyone experiencing unexpected issues with tint strength to report this to your D24 representative or the subcommittee chair (Dirk Roller; ).