A-A-105A
1. Abrasive Content: Accurately weigh 10-12 grams of polish in a tared centrifuge tube. Dilute and dispense polish to 100 ml with hot alcohol or hot distilled water, and then centrifuge at approximately 2000 rpm, for 5 minutes: Decant liquid carefully so as to avoid losing solid matter. Repeat this procedure of diluting, dispensing, centrifuging, and decanting two more times. After the third treatment, place residual solids in an oven maintained at 105o + 2oC for 4 hours. Cool in a desiccators, and weigh residue. Repeat drying process until weight mass is constant. Calculate percent abrasive matter as follows:
% abrasives = (residue weight X 100) /(polish weight)
2. Sieve Test: Weigh approximately 50 grams of polish and place into an 800 ml beaker. Dilute polish to 500 ml with hot alcohol or hot distilled water, cover with a watch glass, and digest on a steam bath for 1 hour. Vigorously stir to dispense solid matter through a tared No. 200 sieve, and then wash with distilled water. Weigh the sieve after drying for 4 hours at 105o + 2oC. retention of any material on the 200 mesh sieve screen shall constitute failure of the test.
3. Tarnish Removal: Materials and Equipment:
(a) Smooth, half-hard, Copper Alloy UNS No. C26000, unleaded, yellow brass panels, each 4”X 6” (10.2 cm X 15.24 cm.)and 1/8” (0.32 cm) thick. The hardness shall be 72-78 on the Rockwell B scale.
(b) A gardener Washability Machine.
(c) Polishing head, rectangular frame fitted with brackets and pins at each end, so constructed to fit the Gardener Washability Machine.
(d) Wool billiard cloth.
(e) A 60” specular gloss meter.
(f) Solution for tarnishing brass, 20 grams of ammonium chloride and 80 grams of cupric sulphate pertahydrate dissolved in 1,000 ml of distilled water at 38oC and cooled to 25oC. for use.
(g) A 7-8 percent aqueous ammonia solution. (by wt.)
Preparation of Panels: A minimum brass of 5 brass panels shall be cleaned and hand polished until etchings or other marks have been removed. Measure the 60o specular gloss of each panel in accordance with ASTM D 523.
Tarnish the 5 prepared panels by immersing for 5 minutes in the beaker of tarnishing solution of ammonium chloride and cupric sulphate. Rinse the panels with tap water and wiped dry with a clean, soft cloth or industrial wiping tissue.
Removal of Tarnish. Each brass panel shall be centered on the pan of the Gardener Washability machine by means of two metal inserts. Fit a clean wool cloth to the polishing head whose weight has been adjusted to 1 pound (454 grams) total weight, and apply 8 ml of liquid or 10 grams of paste polish uniformly to the cloth. Start the machine and continue through 200 cycles. Stop the machine; remove the test panel; rinse under tap water, wipe dry with a clean soft cloth in the direction of the polishing strokes. Determine the specular gloss of each brass panel in accordance with ASTM D 523, and average the results.
Percent Tarnish Removal – (average gloss after polishing X 100)/(original average gloss)
4. Gloss Retention test: Place the five tarnish-removed panels in a desiccator containing 10 ml of 7-8 % ammonium hydroxide solution in an evaporating dish for 30 minutes at room temperature. Remove the five brass panels, and measure the gloss of each. Average the results.
Percent Gloss Retention = (average gloss after 30 min. exposure X 100)/ average gloss before exposure
Percent Weight Loss = (tarnished wt.- cleaned wt.)X(100)/(tarnished wt.)
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