How to polish out glass scratches with cerium oxide

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 (and we recommend professional help in these cases).  If the area feels smooth, you can go straight to polishing.

You will need:

  • some cerium oxide powder for the polishing (mix with water to make a slurry)
  • a polishing pad (suggest soft calico, lambswool, felt or leather) mounted on a backing disc or wheel
  • 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 or masking tape 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 apply mixture to glass and keep moist while polishing

How to Polish

  1. Mix some polish into water to a form a thin slurry (eg. milk-like consistency) - we suggest mixing in a small spray bottle which can be used to apply to polishing pad.  Some people prefer a thin paste. Test which consistency you prefer. The pad can be dampened to help the slurry soak into the 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/tape to identify the area to be worked
  5. Mount pad/wheel in the drill and apply to work area.
  6. Move pad up and down, left and right in work area.
  7. NB:  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. Inspect regularly.
  8. Wipe off residue and inspect repair - keep working until polish is satisfactory
  9. Wash and store pad for later use when it is dry.

IMPORTANT - do NOT let the glass get too hot while buffing - the glass should get warm to the touch for best results but not too hot - control excessive temperature by spraying with water 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. Aussie Sapphire will not be responsible for damage caused by untrained users.

QUANTITY REQUIRED:  we sell cerium oxide in quantities ranging from 100 grams up to 25 kilograms. If you have just a small scratch in an isolated area, then 100 grams will be sufficient.  For a bit bigger job such as a car windscreen, we would suggest 250 grams.  For larger areas, then you will need more but it really depends on the particular job.


NOTE:  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.