Aluminum is a temperamental metal for etching because it starts oxidizing almost immediately after being sanded and neutralized with vinegar or citric acid. To prevent the oxidizing process on aluminum you must deoxidize your plate immediately before etching. Simple deoxidizing solutions for aluminum are:
-4 ounces of citric acid to 1 quart of water or
-2 TBS vinegar to 1 quart of hot water (135 degrees F,
57 degrees C.)
I have drawn through the hard ground, come back the next day and redrawn again onto the plate. Then to etch the plate I used Semenoff’s salt etch and noticed that the prior day’s drawing took 3-4 minutes to start to etch because of the oxidation factor that occurred overnight. The same day drawing on the plate seemed to etch immediately. To make sure that your plate etches evenly, prior to etching, place your plate in a bath of citric acid and water for 3 minutes or vinegar and hot water for 3 minutes.
Then start your salt etch. When applying grounds to your plate first sand and clean with calcium carbonate and water.
Then the deoxidizing solution should be applied. The same procedure should be used for copper except you are using a salt and vinegar solution.
