Polishing 101

I find polishing things somewhat meditative, it's somewhat laborious but satisfying. I thought I'd start with the process of polishing some brake calipers. These are intended for my commuting bike. The process of polishing involves removing a tiny amount of surface material of the object to make it very smooth which gives it a shiny appearance. This is achieved by from a coarse to a fine sandpaper finishing with a polishing compound.

This guide is intended for polishing alloy parts - you can polish chrome plated objects in a similar way but it is easy to overpolish through the chrome plated layer, so bear that in mind.

You will need the following materials:
- wet & dry sandpaper in 400, 800 and 1200 grit
- you may want a slightly coarser grit like 200 if the object has lots of scratches or an anodised finish to be removed
- metal polish such as Autosol
- cotton or wool cloth for the metal polish
- latex or rubber gloves (the aluminium will stain underneath your nails otherwise)

This is the caliper as it was with the factory silver anodising.

These are the Shimano 600 "arabesque" single pivot brake calipers with forged alloy arms. They are silver anodised so this had to be removed with some coarse paper. I used 180 grit dry, generally you would use wet sandpaper as it creates less mess and means the sandpaper won't clog as quickly but this is what I had at hand.

A quicker less laborious alternative to remove anodising is to use oven cleaner, make sure it is the type with Sodium Hydroxide. Be very careful with this stuff as it is caustic, so wear eye and hand protection. Spray the item making sure to cover it completely and leave for 3mins, rinse off and see if it has had any effect, if not repeat the process and double the time. Repeat this procedure until you start to see some results, I had to wait about 15mins to get the silver anodisation off the Shimano 600 derailleurs. If you leave it too long it can etch into the aluminium itself, this is a nasty chemical!

Below is after removing the anodisation with a raw alloy finish. With smaller pieces like this, be sure to get inside every nook and cranny.

From this use the 400 grit wet and dry sandpaper, keep a bucket of water or a tap running and wet the sandpaper. You'll probably want to rip off a small bit of the sandpaper depending on how intricate the piece your sanding is. Sand the object constantly wetting the object and the paper, making sure the aluminium doesn't clog up the paper. Soon enough the paper will wear out and you will need to rip off a fresh piece and continue.

Once the piece is completely sanded with 400 grit like the picture above, repeat the process with 800 grit...

...and then 1200 grit. You will notice that less and less material is being removed and that the surface will start to get a bit of a lustre.

Dry the piece off with a rag and apply the polishing compound with a clean dry rag. Start to rub in the polishing compound.

After one pass you will get a nice shine, to get a nice mirror finish repeat this again with some more polish.

Rub it down with a clean part of the rag to remove the residue and you should have a mirror finish. Over time it will slowly dull with oxidisation and dirt. This will just require a re-polish to bring back its shine. Remember to make the most effort in the early stages, if you can remove all the irregularities with the coarser grades you will get a much better final polish.

Happy polishing.


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