These tumblers are stainless steel and from Walmart for about $10.

First use adhesive stencils. This is personal use and not for sale so I used a image off the internet.

Attach to your cup. Then get some supplies ready:
9v battery
Low voltage wire (old telephone or speaker wire works )
electrical tape
Vinegar
Salt
Q-tips
Container
Scissors

Tape your positive end to the battery and the cup.

Tape negative end to the battery negative post and wrap around q-tip.

Mix up tablespoon of salt and about a 1/2 cup vinegar.

Dip the q-tip in vinegar mix and start etching! Keep it moving, it will bubble or sizzle when it's working. It stinks so this is why you should be outside.
**This is a battery and electric, even though the current is very minimal I still stress to be careful and not let children do this project.**

The longer you stay in one spot the more it removes and the whiter the etching will be. It was 105 degrees outside and I just wanted to be done.

Rinse and clean by hand with soap and water, then double check any spots before removing the stencil.

All done!

We also did the bottom with a joke between my daughter and husband.