Welcome to Matt’s Metalworking, in this tutorial I will be showing you a beginner’s guide on how to polish brass with a mirror finish by hand. I’m just using a piece of raw brass, so you can see it’s quite rough and it’ll definitely be more work intensive than compared to a machined piece or something that is already finished just needing to be refinished.
- bucket with water
- backing pad
- clean soft cloth
- 600 grit wet/dry sandpaper
- 1000 grit wet/dry sandpaper
- 1500 grit wet/dry sandpaper
- 2000 grit wet/dry sandpaper
- alloy polish
Step 1: Preparation Before Polishing
Start by washing the piece to using soap and water. This will help remove any contaminants which may cause damage during the polishing process. Any contaminants can impede itself in the sandpaper or polishing clothes, causing scratches in the surface.
Step 2: First Stage of Wet Sanding
Depending on the surface’s damage, this will depend on what grit of sandpaper is required. For this I am starting out with 600 grit sandpaper, this needs to be a wet/dry compatible paper. The sandpaper needs to be pre-soaked before we start the sanding process. I have a bucket of water beside me, if you wish you can mix in soap to help with lubrication that can allow for a finer finish. For this tutorial, I’m just using straight water.
The heavier surface damage, the lower the grit is required. However when you go to a lower grit, this also means more material will be removed, and as you increase to a higher grit, slightly more work is required to remove those heavier grit scratches. When starting out with that first grit of sandpaper, most of those surface imperfections should be removed. This is basically the rough in step. Rinse off the surface to remove any access sanding material and always keep the sand paper well lubricated.
Step 3: Second Stage of Wet Sanding
Moving up to 1000 grit wet/dry sandpaper. The reason I am wet sanding is so that the dust is kept down and we can achieve a finer finish. The black backing pad I have keeps even pressure on the surface with minimal distortion as what you may find when only using your fingers. For irregular shaped surfaces, you maybe able to use a foam backer instead.
Step 4: Third Stage of Wet Sanding
After a couple minutes of sanding, you’ll noticed the sanding marks are much finer and we can now move onto 1500 grit. Rinse excessive material build up and make sure the sandpaper is well lubricated. Compared to other metals I have polished in the past, I do find brass tends to be a little sticky when moving up to finer grits.
Step 5: Forth Stage of Wet Sanding
Now 2000 grit sandpaper. After this you can take it to another step using 3000 grit, but for this I am finishing with 2000 grit. The finer grits allows you to achieve a higher shine with more clarity.
Step 6: Using Abrasive Pads
For an addition example using an abrasive pad. Just like sandpaper, these too are available in various grits and is typically distinguishable by the color of pad. The maroon pad is listed at about 320 to 400 grit. These can be used with water as well which I am doing here. These pads are great for irregular shaped objects, but they don’t necessarily remove surface imperfections. Instead they smoothen or round off those imperfections. Sandpaper with a backer on the other hand can promote more of a smooth surface.
Moving up to a finer grit, this pad is green and rated at about 600 grit. Always keep the area well lubricated and rinse away excessive material. I’ll be stopping here to demonstrate what happens when you don’t use a fine enough grit before moving onto a polishing compound.
Step 7: Sandpaper Vs Abrasive Pads
This illustration helps explain the difference between using sandpaper and abrasive pads. Starting out with the existing surface and surface imperfections, each has high and low spot. With the sandpaper and a backing pad at the top, this removes all material evenly and also takes down the high spots from cratering marks. If you want those deeper marks to be completely gone, more surface material needs to be removed unfortunately. So this can result in more work, thinner surface, and changed dimensions.
Using abrasive pads, these may leave the surface uneven and won’t remove surface imperfections complexly. Instead it’ll round off those marks and cratering. Which methods you go with is really your personal preference and what type of shine you want to achieve.
Step 8: Polishing Stage
Now moving onto the polishing stage. You can use a polishing compound such as what is used on automative paint or a metal or alloy specific polish. Here I am using an aluminum wheel polish.
I typically start out with soft paper towel first as metal polishing can make clothes quite dirty and hard to clean afterwards. Paper towel can be easily thrown away and we can finish with with a soft cloth at the end. Apply the polish to the cloth and work it into the surface. I will be polishing both the areas I used sandpaper and then the abrasive pads.
Work the polish into the surface, apply more polish when needed, and wipe away if the old polish gets too excessive. The polish will turn black which is perfectly normal as it’s removing a very light amount of material.
Step 9: Finished!
Once the surface is almost finished, finish up with a light amount of polish and a soft cloth.
And this is what we’re finally left with. You may see some mild scratching, therefore more polishing would be needed. There is still some surface imperfection, but they are much less than compared to what we started with. Finishing up with the 600 grit abrasive pad, while it’s still somewhat shiny, it doesn’t have the clarity than compared to using a finer grit. You can also see the existing raw finish before we started on other parts of the brass bar.