This article is an introduction to one of the methods utilizing specific types of mass  finishing equipment, compounds and media.

I hope this information will assist you with some guidelines to make your platinum processing easier and more profitable.

WHY IS PLATINUM SO DIFFICULT TO MASS FINISH?

Platinum is a heavy metal, and it is difficult for many manuals as well as mechanical polishing operations to process because very few understand the characteristics or properties of the metal. Many try to use the same process with platinum as they would with gold or silver and then wonder why the results were not as impressive.

In short, platinum is a rather soft metal in its pure form and needs to be alloyed with another metal. Most of the time it hardens and can be less forgiving than other precious metals.

Certain influences can affect the results of the smoothing and polishing of platinum. Some of these would include the alloy used in the metal, the purity of the platinum, the process being used to smooth and polish it, as well as if the proper equipment and media are being used for a specific application.

Note: It is also extremely important to not let the platinum surface get contaminated. 

We recommend that you keep a clean work area while working with platinum, its own separate media to avoid this problem. If contaminated, it would need to be reclaimed through refining, which is costly.

WHAT ARE SOME OF THE ALLOYS USED WITH PLATINUM AND WHICH ONES WORK BEST?                                                                                              

From a mass-finishing point of view, we have found the following platinum alloys work best in mechanical mass-finishing equipment:

• Tungsten
• Cobalt
• Copper

Other types of platinum alloys studied with less favourable results:

• Iridium
• Ruthenium

Note: Results with the above alloys proved to be less positive after the final polish. Platinum with iridium alloy gave a light greyish tone after mass-finishing. Parts, which were hand, prepared (lightly sanded) came out far better than parts with no preparation.

IT'S IN THE PREPARATION

The quality of the mass-finish depends greatly upon the steps preceding it. Mass-finishing is, or close to, the final-step in many cases and is not a cure for all process. If the alloy, the quality of metal, the casting and preparation (removing the sprue and a light sanding if need be) are not properly performed, chances are that a high luster or quality finish will also not be achieved.

More times than not some initial hand preparation (depending on the condition of the platinum part) can lead to very favourable high luster results. This is especially true if the surface is porous. Manual labour can be largely reduced by using mechanical mass finishing equipment; however, it may not be completely eliminated and there should be some sort of a synergy between hand labour and mechanical equipment.

PROCESSING (CAST VS. HANDMADE):

The process used for cast parts compared to handmade is relatively the same except for the time needed to process cast parts is longer. In some cases, handmade parts were processed using strictly a dry cut and dry polish in the CBF and drag-finishing machines. This was accomplished where the milling machine was able to cut the platinum so fine it was difficult to detect the turn lines.

 MAGNETIC FINISHING:

There is some misunderstanding in the industry as to what magnetic finishing can accomplish. This equipment is not capable of producing a high-end polish. Its purpose is to have the fine pins reach areas where standard media cannot reach such as the inside of prongs. It is also ideal for removing casting powder found inside of concave or pronged areas. Again, the finish in these areas will never be a mirror bright polish, but it will have some lustre and the area will be clean.

It should be noted; however, that the inside of the parts cannot be processed to the same extent or quality as the outside but in most cases the in­ side does achieve a finish about 75% as good as the outside.

IN CONCLUSION:

With the growth of platinum in recent years along with rising costs of manually manufacturing quality products in a timely fashion, we are at an important juncture where the mechanical means of finishing products should be considered. Machinery can assist or, in some applications, completely finish platinum jewellery saving time and money. Basically, it is hard to find, train, and keep good hand polishers today, and the growing costs to keep such help is also escalating. The benefits of machines, although needing some maintenance, is that they do not require a salary (except the initial purchase), they do not have good and bad days, nor do they quit, take vacation, steal or call in sick.

They do not require a costly benefit package, and machines can be a tax write-off over the years. They can even work at night or overtime and will not require time and a half pay. It is even proven that less metal is lost utilizing these machines compared to hand workers.

The processes for finishing platinum are now available, and it is important to ponder if your product can benefit by one of these mechanical means of mass finishing in order for you to be more competitive and profitable.

Author : Parin Waghwala (Dhruvi Creations)