OK so I finally found my book The Now and Zen of Metal Polishing and this is the info on different types of polishes. I thought I would post this part up.
There are so many abrasives out there too. Some better in one application than another. The ability of any abrasive to cut is dependent on three things.
1) Its general size and coarseness or grit.
2) The shape of the abrasive crystal.
3) The hardness of that particular crystal.
The size and coarseness determines how deep the scratch is that any one crystal can make.
How well that crystal can actually achieve its maximum cut is determined by the angles between the edges.
In other words a thin crystal will slice, and a cuboid or round crystal will turn over. If the crystal is relatively soft it will not hold a good cutting edge particularly long. The same applies if the crystal is very brittle. It may cut like nothing in this world, but not for long.
The industry actually develops abrasives with crystals of perfected shapes for various cutting operations. Aluminum oxides make very good general purpose abrasives and come in various grades, but they fail very quickly on harder metals like Chrome and Stainless.
Ferrous oxides used in Jewelers Rouge (which is red and used on gold) are also quick to loose their abrasion next to a chromium oxide.
Chrome oxide is the preferred abrasive for finishing stainless and nickel.
By the same token, while the general stainless compounds are awesome cutters with great mirror qualities, theyused fused aluminas which leave a deep scratch compared to good chrome oxides and calcined aluminates.
So for our finish we go for the softer and less enduring alumina compounds, which have great colouring characteristics but less aggression.
Colouring is the term given to forming a mirror finish, and denotes the ability of the finish to reflect light and colour. Image.
The term actually comes from jewelers using rouge to “Colour” gold, with ferric oxide, because it stains the gold as it polishes.
EMERY is a coarse hard cutting abrasive that is normally the first buffing stage of a polishing job. Leaves a satin finish when applied with sisal wheels.
STAINLESS STEEL compounds, or at least compounds blended to cut stainless, is what I should really say, tend to be good cutting compounds, and give a reasonable start to your mirror. Very necessary when working on stainless and other hard metals.
FERRIC OXIDE is the foundation of jewelers rouge. It peeves me to hear all other abrasives in bar form called jewelers rouge, very often by the industry itself, I might add. Jewelers rouge is made of a synthetic rust, basically. That’s why it’s red. Rouge is french for red. If it is yellow, blue, green, white or any other colour but red, if it is made of any other abrasive than Ferric oxide. IT AIN’T ROUGE!
ZIRCONIUM compounds tend to be quite soft cutting, but cut they will, and very good for finishing chrome, stainless and other metals. These compounds have good colouring characteristics. Very slow cut. Some abrasives using zirconium cut quite well and become progressively finer with use as the crystals break down. This is actually intended, and can in the right situation save going from grit to grit.
Cubic Zirconium on the other hand is quite a hard cutter and will fracture to expose new cutting edges and will progressively cut until the abrasive is exhausted.
TRIPOLI is a fairly good and hard cutting compound, which breaks down very quickly, available in various grades for use on softer metals like aluminum, copper, brass, etc. and also has quite good colouring characteristics.
Infact, tripoli comes from missouri and is a combination of a particular silica and clay which happens to occur only in that area.
CHROMIUM OXIDE tends to be a finer, yet harder cut than tripoli, but comes in some quite fine grades making it suitable for finishing chrome, and stainless. ( It is chrome and nickel that gives stainless its brightness.) it is also very good on nickel, titanium and cadmium. Because it can be of super fine quality it is often used in the dental and jewelry industry, it is replacing jewelers rouge in many quarters. It is also quite expensive as abrasives go.
ALUMINUM OXIDE, the hardest ( Naturally occurring) compound on the planet, only pure carbon (diamond) is harder.
It is a good cutter for aluminum and removes the blueing that you get on overheated chrome.
It will give a nice finish on copper, brass, bronze and soft alloys.
Finer grades have very good colouring abilities. Aluminum oxide is probably the most popular abrasive in industry today.
The crystals are grown in many wondrous shapes and sizes and are available in a wide variety of grades.
ALUMINUM SILICATE gives a beautiful lustre to about everything that you put it on but it is a soft cutter and takes time on harder metals like stainless, nickel, titanium and chrome.
CALCINED ALUMINUM OXIDE is superfine, expensive and gives an awesome finsh on just about anything, but it is a slow abrasive for finishing only.
SILICONE CARBIDE, mean down and dirty aggressive abrasives tend to use silicone carbide. Tough stuff! But it breaks down quite quickly.
SILICA, the most common abrasive of all is the most abundant element on the planet. Under every ocean, in just about every area of the world in some form or another you can find silica, somewhere. Very good in lower grits.
Aluminates and chromium oxides are available in very superfine grades, and can be fine enough for optical polishing, and are often used in scientific applications.
Of course some compounds cut better than others just because of the shape of the crystals they are made from, and generally they cut less as they become finer, but that is not necessarily a hard and fast rule. Some compounds can retain good cutting characteristics at very fine grades. Which means that they give quality finishes quicker.
These are not all of the compounds and abrasives on the market but constitute the most common.
