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How to polish stainless steel to a mirror finish

Posted by Julian Prestidge on 23 April 2019
Julian Prestidge
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A mirror finish on stainless steel is not just aesthetically pleasing, but it has a few other benefits depending on exactly what you're fabricating.  Keep reading to see if a mirror finish is what you really want, and find the processes and products that will get you a great end result!

stainless-steel-finishes-2B-3-4-8What's a mirror finish?

A mirror finish on stainless steel is a highly reflective, smooth finish with a scratch free appearance, achieved through polishing the stainless steel.  Also known as a #8 finish, a mirror finish can be achieved mechanically, using a progressive series of abrasives and polishing compounds. 

Why choose a mirror finish?

Mirror finishes are often chosen for stainless steel products that need to look attractive, like balustrades, architecture, kitchen/bathroom tap-wear, or artworks.  The benefit to a mirror finish, is not just that it looks great, but that it is highly corrosion resistant.  This is due to the polishing procedure which removes deep scratches which can harbor corrosive particles.  This is where mirror finishes are particularly useful in coastal architectural projects which can be exposed to salt air.

How to get a mirror finish on stainless steel

To get to a mirror finish, you'll work your way through leveling the weld, then sanding, progressively using finer abrasives, before polishing for that truly reflective finish.  Here's a step-by-step guide: 

What you'll need:

Deerfos Bora9 SA331 Disc Green Rouge Bar Swansdown Dolly Mop
Deerfos Bora9 Fibre Disc, 60 grit+ Deerfos SA331 Velcro Sanding Discs, P120, P240, P400, P600, P1200 & P2000 grit  3B Green Rouge Polishing Compound Swansdown Dolly Polishing Mop

 

Step 1: Level/remove the weld

If you're aiming for a mirror finish, you're probably wanting your fabrication to look its best, so will want to remove the weld.  If you're not needing to remove the weld, skip to step 2.

Using a Deerfos Bora9 Fibre Disc, P120,  set your sander to 5,000-7,000 RPM and carefully level the weld without gauging or distorting the work

Bora9 Fibre Discs use a new generation ceramic grain for aggressive, cool cutting and long life caused by the sharp crystal shaped grain.  They also utilise a specialised top coating to reduce clogging, friction and heat build up, maintaining the sharpness of the grain.

 

Grinding SS Weld

Deerfos Bora9

Deerfos Bora9 Fibre Disc, 60 grit+

 

Steps  2 : Sanding

Now you've leveled the weld and removed any heavy fabrication marks, it's time to bring these areas up to the base product finish, it's time to sand the whole piece and get it ready for polishing.

  1. Start with a Deerfos SA331 Velcro Sanding Disc, P120 grit and sand over the area you've used the fibre disc on in Step 1, or where you've marked the steel in the fabrication process. Setting your sander to 4,000-6,500 RPM, move at a 90° angle to the scratches made in the previous step so make sure the previous scratches are removed.

The original finish of the stainless steel you are fabricating with will determine how soon you will need to start sanding the whole piece. Sand the fabricated areas until you have them to about the finish of the original sheet, and after you have done this you will then need to start sanding the whole surface.  Repeat each next step:

The higher the mirror finish you want, the more you will need to sand. From this point, the higher you sand, the better mirror finish you will get. These next steps take longer to sand each grit out, to get the prefect finish.


Sanding

SA331 Disc

Deerfos SA331 Velcro Sanding Discs

 

Step 3: Polishing

Wahoo!  Now you should be finished with all that sanding and ready to polish!

Grab your sander with a clean Swansdown Dolly Polishing Mop, and on a slow setting apply some 3B Green Rouge Polishing Compound to the mop (or for a super jewelry like polish use Blue Hubble

Set the sander to 2,000-3,000 RPM, and polish away!

polishing-compound-green-rouge

Swansdown Dolly Mop

Swansdown Dolly Polishing Mop

 

For best results 

  • Clean the surface before sanding - this will reduce the chances of particles getting embedded in the metal, and will also make your abrasives last longer, and with a faster removal rate.
  • After removing the weld, the first sanding should be in the direction of the original metal grain to blend in the weld.
  • At each subsequent stage of sanding, move in a direction 90° from the previous sanding direction.  This will ensure all scratches are removed.
  • Always use a clean polishing mop.  If applying more than one type of polish, clean the fabrication with cleaner and a clean rag in between polishes, and use a clean mop for each type of polish (do not mix) 

 

Need Products?

No worries - shop online for overnight delivery!

Deerfos Bora9 SA331 Disc Green Rouge Bar Swansdown Dolly Mop
Deerfos Bora9 Fibre Disc, 60 grit+ Deerfos SA331 Velcro Sanding Discs, P120, P240, P400, P600, P1200 & P2000 grit  3B Green Rouge Polishing Compound Swansdown Dolly Polishing Mop

 

Topics: Metal Finishing