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Polishing out Glass Scratches with Cerium Oxide


While we supply cerium oxide mainly as a rock polishing compound, it is also used in the glass industry as a polishing agent.

One great use for cerium oxide is polishing out glass scratches and the process is quite simple.  First you need to determine how deep the scratches are - if you can feel the scratch when you run your fingernail over the area, it is likely to be too deep to polish out easily.  In these cases, you will need to grind it down before polishing.  If the area feels smooth, you can go straight to polishing.

You will need:

  • some cerium oxide powder for the polishing
  • a polishing pad (suggest lambs wool, felt or leather) mounted on a backing disc
  • low speed drill (1500 rpm or less) to use with the polishing pad - polishing too fast will generate excessive heat and may crack the glass.
  • a marking crayon to mark the inside of the glass (use this to guide you when polishing)
  • a cleaning cloth to wipe and allow inspection of the work area
  • small spray bottle - use to spray water to glass to keep damp and prevent overheating

How to Polish

  1. Mix some polish into water to a form a thin slurry (eg.cream-like consistency) - we suggest mixing in a small container so you can easily apply to polishing pad
  2. Clean glass thoroughly to remove all traces of dirt and grease
  3. Apply polish mixture to the polishing pad
  4. Mark the inside of the glass with the crayon to identify the area to be worked
  5. Mount pad in the drill and apply to work area.
  6. Move pad up and down, left and right in work area.
  7. Keep the surface wet to prevent glass getting hot - if sufficient polish has already been applied, then just spray a fine mist of water to keep the area cool.
  8. Wipe off residue and inspect repair - keep working until polish is satisfactory
  9. Wash and store pad for later use

IMPORTANT - do NOT let the glass get too hot while buffing - it should be warm to touch but not extremely hot.  Prevent overheating by spraying with water occasionally and keep the buffing pad moving continuously.
 
Deep Scratches
If the scratch can be felt with a fingernail, it is probably too deep to remove by polishing alone.  You will need to grind out the scratch with progressively finer grit.  This is a more specialised (and tedious!) job and it may be best to seek the advice of professionals in these cases.

For valuable pieces, please seek professional advice before attempting a DIY repair. 

NOTE:  we sell cerium oxide in 250g packs with discounts applying for larger quantities.  For small jobs, 250g should be plenty.  See the link below:

CERIUM OXIDE POLISH

Some glaziers will call this product "jewellers rouge" - this is a misleading name as jewellers rouge is actually iron oxide and bright red in colour.  Usually they will actually be referring to cerium oxide - a "peach" coloured powder which is particularly well suited to glass work.  If you want to clean or polish glass - you will normally need to use cerium oxide, NOT iron oxide.