ASTM C474-15 pdf download.Standard Test Methods for Joint Treatment Materials for Gypsum Board Construction.
5.5 Procedure: 5.5.1 Fill the viscosity container with the mixed specimen until level with the top of the container. 5.5.1.1 Remove all air bubbles by puddling the sample container with a spatula and sharply rapping the bottom of the container on a hard flat surface. 5.5.2 Secure the filled container in the center of the viscom- eter spindle platform. Position the spindle so that the sample comes up to the immersion mark on the pin (spindle). 5.5.3 Start the viscometer and record the viscosity reading on the digital display after 30 s. If the viscometer readout goes to a strip chart recorder, read the viscosity after the pen starts to trace a straight line (usually within 1 min); if the tracing remains inconsistent, estimate the average viscosity reading. 5.6 Report: 5.6.1 Report the viscosity of the joint compound specimen in Brabender units. 5.7 Precision and Bias: 5.7.1 The precision of this test method is based on an interlaboratory study conducted in 2011. Seven laboratories using Brookfield equipment and eight laboratories using Bra- bender equipment tested two different materials, by alternative methods. Every test result represents an individual determination, and each lab was asked to report five replicate results for each material / instrument combination. Except for the limited amount of data reported for several of the material / instrument combinations, Practice E691 was followed for the design and analysis of the data. 5.7.1.1 Repeatability Limit (r)—Two test results obtained within one laboratory shall be judged not equivalent if they differ by more than the “r” value for that material; “r” is the interval representing the critical difference between two test results for the same material, obtained by the same operator using the same equipment on the same day in the same laboratory. Repeatability limits are listed in Tables 1 and 2 below. 5.7.1.2 Reproducibility limit (R)—Two test results shall be judged not equivalent if they differ by more than the “R” value for that material; “R” is the interval representing the critical difference between two test results for the same material, obtained by different operators using different equipment in different laboratories. Reproducibility limits are listed in Tables 1 and 2 below. 5.7.1.3 The above terms (repeatability limit and reproduc- ibility limit) are used as specified in Practice E177. 5.7.1.4 Any judgment in accordance with statements 9.1.1 and 9.2 would have an approximate 95 % probability of being correct. 5.7.2 Bias—At the time of the study, there was no accepted reference material suitable for determining the bias for this test method, therefore no statement on bias is being made. 5.7.3 The precision statement was determined through sta- tistical examination of 296 results, by alternative methods, on two materials (described below). 5.7.3.1 Sample A: A representative conventional weight ready-mixed all-purpose joint compound prepared specifically for the round-robin test and distributed to all testing laborato- ries. 5.7.3.2 Sample B: A representative low-viscosity wall tex- ture compound prepared specifically for the round-robin test and distributed to all testing laboratories. 6. Shrinkage 6.1 Significance and Use: 6.1.1 This test is used to measure the amount ofshrinkage in joint compound. The degree of correlation between this test and service performance has not been determined. 6.2 Sampling: 6.2.1 Sampling shall be in accordance with Specification C475/C475M. 6.3 Specimen Preparation: 6.3.1 Specimen preparation shall be in accordance with Section 4. 6.4 Apparatus: 6.4.1 Plastic or Rubber Film, approximately 5 by 5 in. [130 by 130 mm]. Any thin, flexible film that peels clean from a partially dried patty may be used. 6 6.4.2 Balance, having a sensitivity of 10 mg (Figs. 1 and 2). 6.4.3 Beaker, Ring Stand, and Wire Cradle (see Fig. 1).ASTM C474 pdf download.