Alicia:
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
this.
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.
John Walbaum