Of course, there are plenty of high-end brewing kettles that you can purchase that include the volume markings already. However, if you already own a nice 2.5 or 5 gallon setup, you can use a process known as Brush electroplating to etch the volume markings into the metal kettle. Essentially, it will use an electrical current to remove some metal, but only where the stencil is. It sounds a little scary, but you can do it pretty easily and with stuff lying around the house!
The first step is to gather supplies.
The products used in this demonstration are listed at the bottom of the page.
Mark your water levels
Make sure your kettle is level.
Using masking tape, mark each increment where you want your levels to be. I reccomend 1 gallon at a time.
Add Stencils to Measured Levels
Sticker stencils of letters or numerals are best for this venture, since they will stay put and do the best job of controlling the vinegar while the engraving occurs. These ought to be accessible at your closest specialty store. Stick the stencils down precisely where you need them. Getting the stencils perfectly before you start drawing makes the job considerably less demanding.
Mix your vinegar/salt 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 1 tsp salt in 1 cup of vinegar.
Bayou Classic Bayou Stainless Brew Kettle, 40 quart, Stainless Steel
40 Quart/10 Gallon Max Capacity Brew Kettle
Use for Malt Extract Home Brewing or "Brew in a Bag"
Stainless construction enables easier sterilization prior to brewing
1 X Letter and Number Stencil Sets – Sizes 8, 10, 20, 30mm – Assorted Colors
Great for making signs and art projects
Sets include both uppercase and lowercase alphabet and numbers
Smooth die-cut edges provide a sharp outline for tracing
Hook up Your Kettle
Hook the Nine Volt battery positive (+) lead to your kettle. Simply tape it.
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.)
Attach battery to swab
Attach the battery connector’s negative end to the cotton swab. This wire should be in direct contact with the vinegar. Ensure it’s wound firmly around the head of the Q-tip so it stays on while you draw.
Soak the Q-tip in your vinegar solution and touch it to the kettle. If you hear some sizzle sounds 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.
Remember, anywhere you touch the etching tool to the brew kettle will be permanently modified, so be sure to take your time.