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ASTM D4941-06(R2021) pdf free download

ASTM D4941-06(R2021) pdf free download.Standard Practice for Preparing Drawdowns of Artists’ Paste Paints
1. Scope
1.1 This practice covers the production of uniform films of artists’ tube paints and other nonflowing pigmented paints using paint applicators designed for less viscous paints. 1.2 Information on how to achieve opaque specimens from these paints is included. 1.3 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.5 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
4. Summary of Practice
4.1 The paint is spread over the area of the test panel to be covered by the drawdown and the bar is pulled down with pressure just sufficient to avoid lifting of the bar from the chart surface. 4.2 Test panels are allowed to dry in a dust-free environ- ment. 4.3 If complete hiding (opacity) is needed and not produced by a single paint film, a second film is applied at a 90° angle to the first. If required, additional layers may be applied using a narrower drawdown bar.
5. Significance and Use
5.1 Quality standards for artists’ paints require the evalua- tion of various appearance characteristics of paint films. Tinting strength determination (Test Method D4838) specifi- cally requires the preparation of drawdowns for colorimetric measurement. Other evaluations such as color designation, transparency, gloss, and color difference measurements also require drawdown samples. 5.2 Artists’ tube paints have a paste consistency that makes the use of traditional film application methods difficult, espe- cially for drying oil paints. 5.3 Artists’ paints vary in two properties important to the preparation of films, that is, transparency and drying time. Colorimetric determination and some other types of evaluation require paint specimens that completely hide the substrate. Very transparent paints require such a thick film to produce complete hiding that drying times is excessively long or the specimen surface is blemished. When complete hiding is necessary, this practice is designed to provide opaque films without these defects through application of a series of thin films.
7. Procedure
7.1 Attach chart to a firm, smooth, level plane surface using tape, a vacuum plate, or a clamp. Label the chart with the identity of the specimen and other data as required. 7.2 Mix paint sample thoroughly using two spatulas. Tube paints that have separated should be expelled completely and mixed. N OTE 1—The use of coated freezer wrapping paper as a mixing surface simplifies clean-up. The same paper can be used for weighing specimens when required as in the tinting strength determination (Test Method D4838). 7.3 Using a spatula, spread the paint, in a thickness exceed- ing the bar’s gap clearance, over the entire area to be covered by the drawdown. Do not cover the area to be contacted by the supporting feet of the wider of the two bars. Starting at the top of the chart and using the wider bar, draw the bar down over the paint in an even motion applying sufficient pressure to ensure that the resistance ofthe viscous paint does not raise the feet of the bar from the surface. When using oil paints the motion should be slow enough to allow for the high viscosity. Acrylic paints, which have short drying times, should be applied immediately after mixing to avoid premature film formation. 7.4 After drying in a horizontal position for 15 min, specimens may be hung in a vertical position in a dust-free area to complete the drying. Allow 24 h for acrylic and alkyd paints and 48 h or longer for oil paints until dry to touch. 7.5 Examine the specimen for surface defects and discard if unacceptable.

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