In addition to the advice Alma gave you, the quality of your etch
may be degraded by the rather high temperature of your garage.
Eighty- five degrees versus, say, 75 degrees is a considerable
difference on the etching curve. You may want to keep a log showing
time, temperature and other variables if you plan on doing a lot of
Unfortunately, lowering the temperature will make the etch take even
longer. You could try an aquarium pump to aerate the solution
directly instead of the indirect vibration method.