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Cerium Oxide Polishing Compound - Barnesite to Lindsay's and CRL

Updated on March 12, 2012

Cerium Oxide Polishing Compound Can Elimiinate Imperfections

Searching for imperfections in a telescopic mirror at nasa - photo by gsfc on flickr
Searching for imperfections in a telescopic mirror at nasa - photo by gsfc on flickr

Paste And Polish - Cerium Oxide Polishing Compound

The next element in the Rare Earths Grouping is Cerium (Ce). It is second in the lanthanide series with atomic number 58 and that puts it right after Lanthanum from which the series received its name. It is the most voluminous of the rare earth elements which, if you have read the other articles in this array you should know, are actually not that rare at all. As with the other rare earth metals, Cerium has found a diverse range of uses throughout time. One particular compound of great interest is cerium(iv) oxide which is one part Cerium and two parts Oxygen. This fascinating compound has special properties which make it an amazingly efficient and robust polishing compound - cerium oxide polishing compound. It is used by all sorts of hobbyists and professionals for everything from rock tumbling machines to lens high-end telescopes. Car detailers can use it to eliminate scratches from windows and even aquarium builders have been known to use it to restore the walls of the aquarium for their fish. Industrial grade Cerium Oxide like that from the CRL company is used in all sorts of cleaning applications like shower cleaning and more.

The chemical mysteries of the cerium oxide polishing compound and the various slurries and pastes produced from it do not appear to be completely understood at the current time. Like the other rare earths it does seem to have a peculiar ability to remove scratches and shape glass and mirrors in ways that other substances are not capable of doing. The similarity in the composition of rare earths makes them rather hard to separate into completely pure form, or more accurately more expensive, and so the cerium oxide polishing compounds are produced in varying degrees of pureness. This mixture can also tend to be slightly radioactive due to the occurrence of trace isotopes in the natural minerals but opting to buy a more purer compound can reduce this risk and even so, a less pure polishing compound should not present much more radiation than found in the natural environment.

The original cerium oxide polishing compound was called Barnesite and was manufactured by W. F. & J. Barnes Co. out of Rockford, Illinois, who specialized in foot-powered woodworking and metal working tools among other things. They had a catalog with a wide variety of interesting tools and machinery that are still valued by antique collectors and the company was granted a capacious range of patents (View the list of patents here) which in later years came to include a grinding and polishing apparatus for use with the new cerium oxide polishing compound Barnesite. It was about 45% cerium oxide and was an immediate success which led to a legal battle between Ferdinand F. Muenzer (an employee) and his employer Barnes Co. In his court case Muenzer claimed that he had entered into an oral agreement with Barnes that the secret formula would be his, but the argument did not hold up in court and Barnes Co. was free to continue selling the product. Later the Lindsay Chemical Co. developed an improved high-content cerium oxide polishing compound called Cerox which was about 90% pure. The market segment continued to grow and today there is a good deal of suppliers of the pastes and polishes creating prices that are fairly reasonable. Eventually, the original Barnesite was discontinued in part because of federal pollution regulations that the plant could not meet at the time. However, it can still be found on Ebay auctions and there is word that it is being produced again although I could not find such evidence.

Today the cerium oxide polishing products are used by faceters (those who specialize in faceting or shaping and polishing geometric shapes into gemstones and jewelery). Cerium is also known to be used by rockhounds who may spend a month or more with their rock tumbling machines running to achieve that special shine that you may have seen on rocks in souvenir stores and places like Cracker Barrel. Sometimes they use bags of grit, particularly in the latter case, which works to slowly erode portions of the end product. The grit has a mesh measurement with a larger number containing powder with a smaller particle size than a lower number mesh reading. However, the interesting thing found was a sort of grit paradox whereby a lower mesh grit at certain angles of application can actually have a more abrasive effect and remove more material than can a grit of a higher mesh rating. Therefore, it is not just the size that makes for the best abrasive product. There is still something mysterious in the rare earth Cerium. If you want to truly get at the science behind scratches and polishing compounds I would recommend reading some of the articles at this great polishing resource site.

So whether you are an amateur astronomer looking to perfect that mirror while building your first telescope or just looking to remove that pesky scratch from your car windshield, cerium oxide polishing compound will help you leave things clearer than they were before.


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    • john000 profile image

      John R Wilsdon 5 years ago from Superior, Arizona

      This is one fantastic hub about polishing compound with Cerium Oxide. Once you start to read the article it is hard to stop! I polish rocks and never looked into what the contents were. I live in Arizona and have collected a lot of Apache Tears which are obsidian. If you let the tumbler go long enough, the tears can shine like a mirror! I usually wait until they are VERY smooth and shiney and then stop the tumbler.

      Haven't yet read all the Hubs on rare earths, but will now! Thanks.