T.O. 33B-1-11-37(3)Hold the refractometer close to a light source so that the light illuminates and enters the prism.A bright light is necessary. Overhead fluorescent lamps may not furnish sufficient illumination.(4)With the cover plate contacting the prism, look through the eyepiece. Read the Brix value(refractive index units) where the bright and dark areas meet. A clearer meeting line may becreated by adjusting the angle between the light source and the prism face or holding the prismface closer to the light source. Record the refractive index units. Using the manufacturer’sliterature, determine the concentration of the test sample from the refractive index value.(5) When the test has been completed, clean the refractometer cover plate and prism face with a softlint-free cloth. Place the refractometer in its own protective pouch, and return it to the penetranttest kit carrying case.c. When using the hydrometer, perform a water content test in accordance with the following procedure:(1)Mix a test sample of the new hydrophilic remover as recommended by the manufacturer in a500-ml graduated cylinder or similar container.(2)Using the hydrometer, check the concentration of the test sample by noting its specific gravityand recording this reading.(3)Mix the working bath to the same concentration as the test sample within 5%.1.5.5.4.1.1A quick test to determine if penetrant is present in the remover in a large enough quantity to become a possiblecontaminant can be accomplished by passing a blacklight over the surface of the remover in the tank and visuallyexamining it for signs of fluorescence.1.5.5.4.1.2NOTEThe immersion removal time cited is typical. Actual time will depend upon type ofpenetrant, type of remover, agitation and remover concentration. Actual time mustbe determined at each depot or base for each system involved. Trials must beaccomplished using fresh or uncontaminated remover. The objective is to use theminimum time necessary to produce a background-free surface on the immersionpanel when the remover is uncontaminated.Penetrant materials used in open tanks are continuously undergoing evaporationthat may increase the viscosity and also affect removability. Therefore, beforechanging the remover bath, perform the procedures in paragraph 1.5.5.4.1c.A performance check to verify the concentration of used immersion hydrophilic remover baths is required. Thepenetrant from parts disperses in the remover, causing turbidity and a change in the refractive index. The turbiditymakes a color comparison invalid and the change in refractive index is no longer a true indicator of concentration. Theshift in refractive index requires developing a compensation curve for variation with penetrant concentration.Performance testing is the easiest and most practical way of determining the adequacy of a remover bath. The testinvolves processing two roughened panels with different removal contact times and comparing the results using thefollowing procedure:a. PerformanceCheck. Use two oxide blasted, stainless steel panels as described in paragraph 1.5.5.3.2. Atypical processing procedure is as follows:
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