Darkening Brass (Patina)
There are many chemicals and just as many methods available for changing the color of brass. Some chemicals will turn brass black, while others will create a greenish finish. For telegraph instruments, if you choose to artificially color your brass, it is best to go with a brownish color that will yield the "old penny" look because in real life, this is the way brass naturally patinates.
I mentioned in the section on Cleaning Brass that when you are scraping the dirt and crud off the brass, a surface irregularity such as a small dent or pre-existing deep scratch might cause you to accidentally create a tiny scratch in the brass. This can be fixed by wiping the shiny scratch with the tip of a toothpick dipped in Brass Black brass darkener.
Although Brass Black is good for darkening very small spots or scratches, I have found that it does not work so well on large areas because the resulting finish has a very uneven color, with different areas looking either brownish, orange or bluish. Essentially it produces a bit of a rainbow finish, which is not what you want.
Over the years I tried many different suggestions on how to patinate brass but none of them really gave me satisfactory results. I finally discovered a recipe for a patination chemical that gives fairly decent results. The finish is not as dark as an "old penny" but at least it has a nice even brownish color.
To make this patination chemical, you will need the following:
- 1 Cup Distilled Water
- 2 Tablespoons Miracle Gro Plant Fertilizer
- 3 Teaspoons of Novacan Black Patina (used by people making stained glass windows to darken solder)
Mix the ingredients thoroughly in a cup, making sure the Miracle Gro completely dissolves.
Next, polish the part with Flitz Metal Polish, remove all residue and wipe thoroughly with Denatured Alcohol to de-grease the part.
Now, in order to darken the part, you will need to suspend the part in the patination solution with a piece of sewing thread. The thread is then tied to a pencil which is placed across the top of the cup holding the solution. This can be a bit tricky because you don't want the thread touching the part or it will not darken in that spot.
For a knurled thumbscrew, I like to tie the thread around the threaded part of the screw at a point where the knurled thumbnut will be located. This will hide the light spot. If you like, you can darken that small spot later with Brass Black.
For a nut, you need to find another screw to put into the threaded hole then tie the sewing thread to that screw. Just use an off the shelf screw of the same thread pitch that you can find at a hardware store. If the nut mates with a non-standard screw (which often is the case with very early landline instruments), then find a screw of similar size but different thread pitch and screw it part way into the threaded hole. This will allow the screw to grab onto the nut and stay in place during the process.
For other types of parts, you will have to devise a way to attach some kind of "handle" to the part for which to attach the sewing thread, keeping in mind that you want every area of the part to be exposed to the patination solution to prevent any light spots from occuring.
Last, put a piece of aluminum foil on the stove, place the part on it (with the thread and pencil attached but not on the hot part of the stove) and heat it to low-medium temperature. Lift the pencil to remove the part from the stove and immerse the part in the solution, placing the pencil across the top of the cup. Leave the part immersed for 15-30 minutes, depending on how dark you want the part. Check it every 5 minutes or so to monitor the progress.
When the part reaches desired darkness, remove from the solution and rinse in water. Sometimes you might find that some of the new patina will rinse off. If this happens, you might need to repeat the process to increase the level of darkness.