Blackening not only protects bare steel from rusting, but the process also yields a relatively attractive finish. You can achieve this finish with some pretty common household items. You will need:
- clean rags
- motor oil
- handheld torch
- heavy leather gloves, jacket (welding attire works great), and safety glasses
- fire extinguisher (just in case)
- metal or glass bowl (preferably one you don't care about)
- outdoor space conducive to mischief
must be outdoors
clear area of all flammable items
you will spill oil and sometimes that oil will be on fire. asphalt or concrete are ideal--a tarp probably won't cut it
Step 1: Prepare Metal
Using acetone and a clean rag, wipe off excess oil, rust, etc off of your metal parts. You might also use steel wool or a scotch brite if you need a little more abrasion. This would probably have been a good time to be wearing gloves. If you don't have any or choose not to wear gloves, be sure to thoroughly wash hands after this process.
Step 2: Douse, Quench, Douse, Quench
This is where the process needs to move outside for sure. Hopefully you can get an idea of the setup from the photos in this step. I have annotated them for clarification.
Here is the process:
1. set up workspace. lay out rags to place your parts. I laid out two so that I could separate finished from unfinished.
2. wear safety gear and bring fire extinguisher outside with you...just in case
3. pour motor oil into bowl, about 2 cups were more than enough for me. It really depends on your bowl and your part. Make sure that you pour enough oil so that your part(s) can be completely submerged
4. light torch and adjust flame to something manageable
5. submerse a part completely in the oil and retrieve with pliers
6. hold part over flame, moving slowly as to evenly burn off the oil. The oil coating your part will ignite but will burn out soon. note that during this part you will drip oil on/around the torch. it may light on fire but should also quickly burn out. do not be alarmed unless flames grow
7. when oil has burned off and your part is a reddish color, drop it in the bowl of oil, or "quench" it in oil.
8. retrieve the part once again with the pliers. dropping the part and retrieving with pliers may seem unnecessary, but if you hold onto the part the whole time with the pliers, you will end up not blackening the bit clamped between the pliers. If you want an even finish, you should drop and retrieve each time
9. repeat process 2 or three times per part to achieve desired finish
10. place finished parts on rag and let cool
11. wipe off with clean dry rag
check out this great ehow article--which is where I learned a lot of this process!