I use this etchant with aluminum but it is also effective for zinc and steel. When used with aluminum, there is no need for rosin because the metal will effectively aquatint itself.
- 1 kilogram Copper Sulfate – commonly found as a root killer
- 1 kilogram pool salt or kosher salt*
- 50 grams sodium bisulfate – commonly sold as pH Down pool conditioner
- 4 gallons or about 15 liters distilled water
This etchant is based on electro-chemistry and is not corrosive in the sense of traditional etching acids like nitric or hydrochloric. Copper sulfate produces no harmful gases. You will see very small and harmless amount of hydrogen gas bubbling up. Copper sulfate can irritate the skin but brief contact shouldn’t pose a problem. A gloved hand would of course remove any risk. Do wear a particle mask such as N95 when handling the dry powder. Avoid pouring it down the drain, as it is harmful to marine life.
Notes
- It helps to have a large tray or vertical tank filled with etchant. A small tray of etchant can be depleted quickly.
- The etchant loses strength with use and can regenerate itself over time with oxygen and lowered pH by re-dissolving the elemental copper that floats during etching. Make sure this reddish sludge remains in the etching bath. Adding more copper sulfate will also strengthen the etchant.
- Use salt that does not contain calcium silicate, which will form Plaster of Paris in the bath.-link