This article appeared in Make: Vol. 40.
This article appeared in Make: Vol. 40.

As a homebrewer I often need to measure my kettle volumes at various stages during the brew day — to figure out my brewing efficiency, or monitor evaporation rates, or compare boil volumes to what my recipe estimated. Unfortunately, a lot of brew kettle manufacturers don’t put volume markers on their wares.

Some brewers install an expensive sight glass into their brew kettle to monitor volumes. Some brewers dip a homemade measuring stick into the wort. I used to use a measuring stick, but I got sick of relying on an extra tool during brew day, and I didn’t like the added risk of contamination from dipping the stick into my cooled wort. I wanted a permanent solution built right into the kettle that would always be reliable.

While researching metal etching, I came across a technique commonly used by knife makers to leave their brand on their knives. This technique involves electrolytic acid etching. It sounds complicated, but I’ve adapted it to require nothing but cheap household materials.

The basics of the process are very simple. It etches a mark on the surface of the metal by passing a very low-voltage current through the metal in the presence of acid.

In this technique, you’ll use vinegar for the acid. To facilitate this process, the vinegar must be conductive, so you’ll simply add an electrolyte, in this case, salt.

The power source should be around 9 to 12 volts DC, to leave a frosty white mark that’s permanent. I recommend a 9V battery.

To apply the acid and the current, you’ll construct an etching tool out of a Q-tip. The cotton head of the swab will hold the vinegar solution, and the wire will receive the current from the vinegar-soaked cotton.

This method is not limited to kettles or volume markings. You could add a logo to nearly any piece of metal equipment (in either aluminum or stainless steel). Imagine your custom logo all over your homebrewery!

How It Works

Here’s the science behind it: In the vinegar, the salt dissolves into positively charged sodium ions and negatively charged chloride ions. This allows current to travel through the solution. In the presence of acid (vinegar), the electrical current causes the ions in the metal to dissolve so they can travel in the direction of the current, which, in this case, is away from the metal. This permanently removes metal from the surface, which changes its texture. The different texture reflects light differently — making the markings permanently visible. The reaction also produces carbon dioxide, which causes the fizzing. This is the opposite process to electroplating, which would be the result of reversing the polarity.

What about corrosion risks? Stainless steel and aluminum both naturally form oxidized coatings on their surfaces when exposed to oxygen. This oxidized layer is what protects them from rust and corrosion. A few seconds after etching, the surface of the etched area will oxidize again and will be the same as the rest of the brew kettle, thereby protecting it. Still, before etching your expensive brew kettle, I strongly recommend testing this process on another piece of metal that you don’t care as much about, or a very inconspicuous area of your kettle such as the inside of the lid. You don’t want any surprises.

CAUTION: Some stainless steel alloys include chromium and may produce trace amounts of hexavalent chromium , a known carcinogen, when electro-etched. Wear disposable gloves when etching, and rinse the etched metal object thoroughly under running water before using it.

Project Steps

Mark the water levels.

Make sure your kettle is level. An uneven surface will cause the water levels to be off.

Fill the kettle with water, in the increments that you wish to have marked on your kettle, and mark each water level with tape as you go. You’ll want to use tape that won’t lift off while underwater. I poured 1 gallon (3.8L) of water at a time (make sure you trust the container you’re basing your measurements on).

TIP:If your container has straight walls, you can measure the gap between 2 water levels and repeat the measurement up the wall of the kettle.

Apply more tape to create stencils around each bar-shaped area that you’ll etch as a level marker. (You can see this in Step 6 below.)

Alternatively, you could use a wax pencil or grease pencil, but I liked the sharp lines I got from using the tape as a stencil.

Apply stencils.

Adhesive stencils of letters or numerals are best for this project, since they will stay put and do the best job of controlling the vinegar during the etch. These should be available at your nearest craft store.

Stick the stencils down very firmly in place, exactly where you want them. Getting the stencils just right before you begin etching makes the project much easier.

Mix your acid/electrolyte solution.

Combine your vinegar and salt, then give the solution a good shake or stir to dissolve the salt.

The ratio isn’t that important — you just need enough salt to allow current to pass through. I used ¼ tsp salt in ¼ cup of vinegar.

Hook up the kettle.

Hook the 9V battery snap connector’s positive (+) lead to your kettle. There’s nothing fancy about this connection. You can simply tape the bare wire directly to any part of the kettle.

This connection will essentially electrify your entire kettle with a very low voltage, preparing it to be etched at any location on its surface. (Don’t worry, the current is so low that you can safely handle the kettle without danger, exactly the same as touching both ends of the battery itself.)

Prepare your etching tool.

Attach the battery connector’s negative (–) lead to the head of the cotton swab. This wire will need to be in direct contact with the vinegar solution. Make sure it’s twisted tightly around the head of the Q-tip so it will stay connected while you etch.

I found that the wire will actually dig into the cotton, so I didn’t need any tape for this step, but you can use tape if needed.


CAUTION: Some stainless steel alloys include chromium and may produce trace amounts of hexavalent chromium, a known carcinogen, when etched. Wear disposable gloves when etching, and rinse the etched object thoroughly under running water before using it.

Dip the Q-tip in your vinegar solution and touch it to the kettle. If you hear some sizzling or see some bubbling, it’s working. It only takes a few seconds of contact to permanently dissolve some metal. Keep the Q-tip moving. If it stays in one spot too long, it will make uneven marks.

NOTE: As you etch, your Q-tip will absorb by-products of the reaction and start to change color. In my experience, this did not affect the etching.

Remember, anywhere you touch the etching tool to the brew kettle will be permanently modified, so be sure to take your time.

Once you etch the first couple of hash marks, rinse them off and check your work. Are they etched enough? Etched equally to one another? Check now to get a good sense of how much etching is needed for each mark, and check again as needed.

When all your markings are etched to your satisfaction, disconnect the battery, pull your stencils off, and rinse under running water. Your kettle is etched!


This method is not limited to kettles or volume markings. You could add a logo to nearly any piece of metal equipment (in aluminum or stainless steel). Imagine your custom logo all over your homebrewery or workshop!

Share your build using #makeprojects!