Hi, A Keris is a Indonesian blade made of several metals, mostly iron and nickle. To bring out the pamor (contrast in metals) the Empu will clean in fruit acids and then bath in a arsenic solution. Collectors in the US will use arsenic trioxide in a paste made with limes and then rinse with water. I assume this in not environmentally sound to rinse into Metropolitan sewers. A. Is there a way to safely treat this waste? B. Is there other safer chemicals to cause the iron to turn black & the nickle shine? Thanks