Secrets of Cerium Oxide

Since the early fifties Cerium Oxide powders have been used in the glass industry for removing light scratches and other blemishes from vehicular and architectural glass.  Cerium Oxide powder is made from the two minerals bastanite and monazite.  Bastanite is a complex fluorocarbon, and monazite is a phosphate.  
If you venture into the caves of most any glass shop these days you will find a small bottle of cerium powder on the back shelf. Along with a circular sponge pad about an inch thick which is used on a rotary drill motor.  The cerium is usually mixed with a little water, applied to the glass, and then worked for several minutes with the drill.  This is actually somewhat effective at removing scratches that are barely visible but cannot be felt with a fingernail.  If the process takes too long it is not continued and is given up.  Simply because it is not considered cost effective.  What I want to accomplish by means of this article is to show that there are more efficient ways to remove light scratches and blemishes from glass.  That means in other words that we can do the same thing or better in less time.  Lets look first at the polishing pad itself.  I use a ring shaped pad made of hard felt.  Not a light weight foam.  The felt fibers have microscopic hooks that catch the polishing particles and help to drive them into the glass surface.  Felt is also much more efficient at holding onto said particles so they can be used over a greater time.  An optimum sized felt ring used for removing light scratches should have an outside diameter of three inches, and an inside diameter of one and a half inches.  It should also have a crack and peal backing so it can be quickly applied to a thin aluminum  or wooden disk.  The disk has a small universal joint centered between itself and the shaft of the drill motor. This makes it possible to operate the drill at speeds in excess of 1200 rpms without the problem of “bobbing”.  Which allows for perfect contact at all times.  The hard felt will more effectively drive the cerium particles into the glass surface. And since cerium is chemically reactive with glass, the higher temperatures that this more advanced process creates will accelerate that reaction.  You will notice by feeling the new dry surface with a dry fingertip, that it is much more rough than the original window glass.  This proves that the polish is cutting into the glass.  Cerium Oxide reacts with glass  to create a complex new surface of cerium, oxygen, and silicon.  This is softer than a soda lime glass matrix , and is therefore more easily removed by the abrasive action of the polishing particles.

The compound that I use is a fifty/fifty blend of pure cerium and glycerin.  It can be easily transferred to an oral syringe.  To remove light scratches you must first clean the glass well.  Then you can use the compound straight or along with some water.  You might apply some clean soapy water to the glass.  Then put several drops of compound directly onto the hard felt ring.  Next put the polishing ring against the glass and start polishing.  To check the surface just clean the cerium and inspect.  If you need to continue just apply more water and resume.  If you want you can polish with the compound alone. Although using soapy water will stretch out the compound much further.  Also water does assist with the chemical reaction and speeds up the polishing process.
The compound I have chosen and use is based on an ultrapure powder designed specifically for one step glass polishing.  It has a high purity rating with just the right shaped particles.  Which have the tendency of rubbing the glass more then cutting it as diamond does.  Cerium will always create a much smoother surface.  When the powder is suspended in just water it actually improves over time.  I have developed a Micro Wobble Wheel for small area stain and scratch removal.  Also I am working on different lapping rings made of hard felt and some other somewhat more exotic materials.

Written by Henry Grover Jr.

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