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Designation: D7540 − 26Standard Practice forDispersion of Chromatic Pigments with a MechanicalMuller 1This standard is issued under the f i xed designation D7540; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (´) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This practice is intended to be used to disperse achromatic pigment for subsequent testing.1.2 This practice does not apply to white pigments.N OTE 1—The dispersion portion of Test Method D3022 is similar to thispractice, but it utilizes a miniature sandmill rather than a mechanicalmuller, to disperse the chromatic pigment.N OTE 2—The dispersion portions of Test Methods D332 and D2745 aresimilar to this practice, but they are intended for use with white pigments,rather than chromatic pigments.1.3 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.4 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.Specif i c hazard statements are given in Section 8.1.5 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards: 2D332 Test Method for Relative Tinting Strength of WhitePigments by Visual ObservationD2745 Test Method for Relative Tinting Strength of WhitePigments by Ref l ectance MeasurementsD3022 Test Method for Color and Strength of Color Pig-ments by Use of a Miniature Sandmill (Withdrawn 2020) 3E284 Terminology of Appearance3. Terminology3.1 Def i nitions—Def i nitions of appearance terms used inthis practice may be found in Terminology E284.4. Summary of Practice4.1 Pigments are dispersed in a suitable vehicle with amechanical muller. Test and standard pigments are treatedidentically. Opaque drawdowns may be made from the disper-sions and compared for color and strength differences eithervisually or instrumentally.5. Signif i cance and Use5.1 The results obtained with a mechanical muller do notnecessarily correlate directly with an industrial situation wheredifferent dispersing conditions exist. However, dispersion witha mechanical muller is a quick and inexpensive way to preparespecimens for testing the color and strength of a pigment forroutine quality control.5.2 By following the procedure described in Annex A1, theconditions for achieving the maximum practical degree ofdispersion with a mechanical muller shall be determined. Anycolor and strength tests done with the dispersions shall becarried out under these conditions.6. Apparatus6.1 Balances—(1) A balance sensitive to 10 mg, and (2) ananalytical balance sensitive to 1.0 mg.6.2 Muller, Mechanical, equipped with ground-glass platesto which a variable but known force may be added in 220 N(50 lbf) increments. The driven glass plate shall have a speedof rotation of between 70 r ⁄min and 120 r/min and theapparatus shall have an arrangement for pre-setting the numberof revolutions in multiples of 50. See Fig. 1 for an example ofsuch a device.1 This practice is under the jurisdiction of ASTM Committee D01 on Paint andRelated Coatings, Materials, and Applications and is the direct responsibility ofSubcommittee D01.24 on Physical Properties of Liquid Paints & Paint Materials.Current edition approved June 1, 2026. Published July 2026. Originally approvedin 2009. Last previous edition approved in 2019 as D7540 – 09 (2019). DOI:10.1520/D7540-26.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at www.astm.org/contact. For Annual Book ofASTM Standards volume information, refer to the standard’s Document Summarypage on the ASTM website.3 The last approved version of this historical standard is referenced onwww.astm.org.Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1