I know it's been a month, but next time try brewing an entire can of coffee into about a Gallon of water. The etch takes a few hours but gives a much better contrast. Your silvery areas stay very bright and your dark areas go dark, but without the "Blurring" that stronger acids like ferric chloride do. The picture is not my work but Tapforge from Reddit. He is the one that told about the coffee etch.