We supply a range of grades of a specially produced oxide.

As inorganic products they show one great advantage over natural materials used for polishing. That being the constancy of their physical and chemical properties no matter at what temperature or under what pressure they are used.

The aluminium oxide is in the form of agglomerates that consist of numerous primary crystals. The size of these crystals depends on the degree of calcination. Generally the higher the calcination temperature the larger the primary crystals.

Grades with larger crystals can be used for grinding and lapping while smaller crystals lend themselves to equalizing and smoothing the surfaces on which they are being used without removing great amounts of material. On car and aircraft bodies for example.

The primary crystals of the aluminas are extremely hard. They rank at 9 on the Mohs scale alongside corundum, and one level below diamond.


Further Information

Polishing aluminas are used in many processes and applications.
Precision lapping, final lapping, hydro abrasion, and polishing.

The benefits of calcined alumina are

- crushing properties of  the agglomerates and primary crystals
- hardness of the primary crystals
- grain shape on both damaged and undamaged crystals
- high melting point.
- resistance to thermal shock
- oil absorbtion
- workability
- the purity of the powder

The balance of cutting and abrasion are the markers by which the decision on the most suitable grade for any application is made.

- Cutting effect is measured on a scale of 1 to 10. 1 represents a very low cut, whereas 10 represents a high degree of abrasion.

- Polishing effect works in a similar way. A level of 1 giving a highly reflective finish, whereas level 10 would give a lustrous finish.

Calcined alumina can be used alone, or in a combination with other materials in a compound.
Compound binders usually involve the use of an oil or wax. The ratio of liquid/paste to solid content is generally around 50/50 or thereabouts.

Method of delivery

- In a suspension with oil, water, or other chemicals
- Without additives
- As a paste
- Mixed with emulsions
- blended into the matrix of a solid polishing bar

The above can be applied manually, or in automated processes in car plant production lines, airless processes and other.

Other applications

- Brake linings
- Household cleaners
- Car cleaners
- Car polishes
- Stone polishes
- Vibro finishing

The Bayer process

In the late 19th Century the search was on to find a mordant, or fixer for textile dyes. In fact what was found was to revolutionize not only the metal industry, but several others too, including surface treatment.

In Russia Carl Josef Bayer discovered that aluminium hydroxide that precipitated from his alkaline solutions was crystalline in  form and so could be easily filtered and washed, as opposed that which precipitated from an acidic solution which was gelatinous, and so difficult to handle. The year was 1887.

Bauxite, in its raw form, contains only 30 – 50% aluminium oxide, the rest being in various proportions, titanium dioxide, silica and a variety of iron oxides. The aluminium oxide must therefore be refined/concentrated before it can be processed into either aluminium metal or the alumina powders used in polishing, refractory, ceramic  and other applications.

Initially the raw bauxite is washed in a solution of Sodium hydroxide at 175 degrees centigrade. The aluminium oxide in the bauxite thus becomes Sodium aluminate.

As the impurities in the bauxite do not dissolve they can be easily filtered off. The resulting red mud is highly toxic (Reference the Ajka Alumina plant disaster in 2010 when huge quantities of red mud were discharged into the Danube).

Next the alkaline solution is cooled and aluminium hydroxide precipitates out. This precipitant is then calcined and hydroxide decomposes to oxide giving off water in the process.

Thereafter there is a divergence as the alumina to be used for aluminium metal production, and that destined to become the alumina powders such as those that we supply begin to take very different routes.