METALS and their OXIDES

As a basis for establishing the relative effectivenesses of subsequent additives, dusts of various metals and their oxides were tested at timed intervals. The ends of small tubular pastic applicators were dipped in shellac, varnish or polyurethane varnish (Fig. 1). While still "wet" these were dusted with the various dusts, and then allowed to "dry" on a peg board (Fig.2). These were then dabbed with silty water to provide a wide variety of microbes (Fig. 3), excess water was flung off, and at timed intervals these were printed onto nutrient agar.

Fig. 1: Clara Watkins, WW2 photographer, coating the ends of PVC applicators with different concentrations of cupric chloride, these were then set in a peg board (see Fig. 2) to dry. Fig. 2: A peg board made of nails upon which an array of applicators can be dried. Fig. 3: Frank Gerdin, Purple Heart (Iwo Jima), dabbing silty water onto the applicators prior to printing them at timed intervals onto nutrient agar plates.

In order to increase the relative surface area of one coinage metal - silver, it was tried in its colloidal form and mixed with small amounts of paint.

RESULTS: As expected from previous tests on coinage metals, some metals were not effective and, with the exception of colloidal silver, those used in coinage were slowly effective taking up to 24 hours to become sterile. Copper chloride was effective in both polyurethane (Fig. 4) and regular varnish (Fig. 5). Paint dosed with colloidal silver became sterile within 15 minutes. As could be seen on the painted, touchable sample at the display (Fig. 7, not shown here), copper chloride had marked contributions to both color and texture.

Fig. 4: A Time/Concentration Study of Copper Chloride in Polyurethane. Applicators coated with polyurethane doped with an amount of copper chloride were dirtied with a slurry of garden soil and then printed onto the nutrient agar surface either immediately after handling or 24 hrs later. Concentration "a" was a slurry of 80 %al with each subsequent concentration (b-f) half that of the previous. "Zero" contained no dopant. As seen here on the plate of printings made immediately after handling, "a" has no growth, and "b" only a small amount. Thereonafter, growth was accessive and deemed ineffective Fig. 5: A Time/Concentration Study of Copper Chloride in Varnish. This is similar to the previous except that oil-based varnish replaced polyurethane. As shown here, the effectiveness of copper ion was somewhat more potent in varnish than in polyurethane - both short-term and especially long-term. .


Fig. 1: Clara Watkins, WW2 photographer, coating the ends of PVC applicators with different concentrations of cupric chloride, these were then set in a peg board (see Fig. 2) to dry.	Fig. 2: A peg board made of nails upon which an array of applicators can be dried.	Fig. 3: Frank Gerdin, Purple Heart (Iwo Jima), dabbing silty water onto the applicators prior to printing them at timed intervals onto nutrient agar plates.