From Rough Cast to Mirror Shine: The Art of Polishing Brass by Hand and Machine
How to Polish Cast Brass to a Mirror Finish: A Step-by-Step Guide
Step 1: Plane and Shape With a Table Belt Sander
The first goal is to flatten the surface and remove any casting marks or rough texture. Cast brass typically comes out of the mold uneven or pitted, so you’ll need to plane it smooth before you can even think about polishing.
I start with a table-style belt sander, working through these grits in order:
120 grit – Removes major imperfections and high spots.
240 grit – Smooths out the deep scratches from the first pass.
400 grit – Starts refining the surface texture.
600 grit – Leaves a consistent, pre-polish surface.
⚙️ Tip: Spend extra time at this stage. The smoother and flatter your brass is now, the easier it will be to bring out a flawless reflection later. Deep scratches you ignore here will come back to haunt you.
Step 2: Refine the Surface With an Orbital Sander
Next, move to an orbital sander to eliminate directional marks and further refine the surface. This step transforms the dull sanded brass into a satin sheen that’s ready for polishing.
Progress through these finer grits:
800 grit – Blends the 600-grit marks and evens the tone.
1200 grit – Starts revealing a soft, subtle shine.
2500 grit – Leaves a near-glossy surface that’s ready for buffing.
🧽 Pro tip: Wipe the brass clean between grits to avoid dragging coarse particles forward. Cross-sanding (changing direction slightly between grits) helps catch leftover marks.
By the end of this step, the brass should already start catching the light — a preview of the mirror to come.
Step 3: Apply a Cutting Polish on the Bench Buffer
Now comes the transformation stage: machine polishing.
Start with a cutting compound on your bench buffing machine.
Use a stitched cotton wheel for firmness and control.
Apply a generous layer of cutting polish to the wheel.
Keep the brass moving across the wheel to prevent heat buildup.
This step removes the ultra-fine scratches from sanding and begins revealing real reflectivity. You’ll see the brass “wake up” here that first burst of shine is always rewarding.
Step 4: Medium Polish for Clarity and Depth
After cutting polish, switch to a fresh buffing wheel and load it with a medium compound.
This stage refines the surface even further, enhancing clarity and depth in the reflection.
The brass will now start taking on that glassy look, where reflections appear sharp but still slightly soft-edged. This is where the surface starts feeling alive almost liquid in appearance.
Step 5: Fine Polish for a True Mirror Finish
For the final machine stage, use a fine polishing compound on a soft, unstitched wheel.
This removes micro-marring and haze from previous compounds, producing a deep, flawless mirror finish.
Use light pressure and steady, even movement. The reflection should now be crisp, clear, and highly luminous.
💡 Tip: Avoid overloading your wheel with compound a little goes a long way. Too much can actually dull the finish.
Step 6: Final Hand Polish With Microfiber
Finish the process with a clean microfiber cloth, using no compound at all.
This last hand polish wipes away residue and gives the brass that unmistakable final gleam.
If you can see your own face clearly reflected you nailed it.
The Reward: A Mirror That Lasts
Polishing cast brass to a mirror finish is equal parts technique and patience.
Each step builds on the last skip one, and you’ll never reach that perfect shine. But when you get it right, the result is more than just polished metal it’s craftsmanship you can see and feel.
Whether you’re restoring antique hardware, finishing a custom part, or just love the satisfaction of a flawless shine, this workflow delivers professional, repeatable results.
🔧 Quick Recap
Plane with belt sander: 120 → 240 → 400 → 600
Orbital sanding: 800 → 1200 → 2500
Buffing sequence: Cutting → Medium → Fine compounds
Final step: Hand polish with microfiber
