What is good metal polishing practice?
Is it true that the metal polishing industry deliberately perpetuates some of the myths and bad practices? In some cases perhaps, whilst in other cases, it may just be common errors of judgement.
It is now possible to discover why brass and copper crack and why some polishes will deteriorate by themselves in good environments.
All will be explained so be ready to see some interesting facts.
Myths, Half-Truths & Lies
Many of the statements you are about to encounter are controversial and fly in the face of what is considered by many as good metal polishing practice. Some of these myths are perpetuated by the industry deliberately whilst others are just errors of judgement. You will discover why brass and copper crack, and why some polishes will deteriorate by themselves in good environments. All will be explained so be ready to see some interesting facts. What follows is the inside story that the manufacturers do not want you to know.
All Metal Polishes Are The Same
Anti-oxidants, enhancers, grime removers, inhibitors, slip agents etc vary enormously from brand to brand.
All Metal Polishes Will Protect
Polishing will normally protect any surface to some degree. However many metal polishes contain ammonia or what is termed anhydrous derivatives. These often appear in new and many old trusted and established products including household names. They are the industry standard and have recently been proven to cause premature ageing of many alloys especially brass and other copper alloys. Minute cracks and fissures appear after excessive use of ammoniates or anhydrous products. Also, these chemicals will increase the tarnishing of the piece in the long run and cause the item to lose its lustre fairly quickly. This means that even in a perfect, stable environment the items will need re-polishing. Manufacturers sell more products which are good for business but bad news for your precious antique heirloom.
Polishing with the correct product will increase the life span of any piece if it is done correctly whereas the use of ammonia and anhydrous products has been proven to do the opposite. A few manufacturers use mild acids instead of ammoniates or anhydrous, the result being that the acids etch into the metal instead. One of the main things that make anhydrous chemicals so bad is that they will dissolve zinc, a major component of brass, and nearly always present on aluminium castings. Zinc is also often used to stop steel from corroding. Anhydrous chemicals can destroy these materials.
The manufacturers that use acids are no better than the others, they still damage your pieces.
All General Purpose Metal Polishes Are Good On Any Surface
A polish that is good on stainless steel or chromium should be kept away from most soft metals, especially gold, silver, platinum, pewter, copper and precious pieces. If it is hard enough to cut stainless steel it will gouge soft metals easily and remove unnecessary material.
If it is good for finishing aluminium it probably will not touch chromium, bronze or stainless steel. That is not to say that polish for fine or precious metals will not work on harder metals, it will simply cut slower. But a polish suitable for cutting hard metals from rough finishes will tear gold and silver apart.
Rapid Acting Liquid Polishes Are Not As Good As Pastes
Generally speaking yes they are, and more often than not, they are better.
The downside with pastes is that they tend to be harder to remove, especially if they get to dry out on your piece. They also tend to leave masses of dried polish in any small grooves or cracks leaving those ugly white lines. While liquid metal polishes tend to dry out to just a powdery residue, they are much easier to remove than pastes.
All Polished Finishes Have The Same Endurance
Unfortunately not because some fade quickly especially when metal polishes that contain ammoniates or anhydrous are used. The ones that use acids are not generally far behind them. But there are also many others too.
Lack of endurance can be caused by all manner of reasons. Lack of inhibitors, lack of protective waxes, or even the wrong waxes for the environment the finish has to endure. A bad pH balance caused by the use of acids or alkalis or even the protective wax, which is normally acidic, is another reason metal polish will fade.
All Polished Surfaces Should Be Waxed Or Lacquered For It To Really Last
Not true, this depends on the environment.
Pieces subjected to ocean environments need protection with lacquers or clear coats.
Show vehicles want their brightwork to be waxed where it counts. Aluminium is normally waxed to improve the lustre, but with stainless steel, it depends on the quality of the finish. Show chromium should never need more than ultra-fine wax-free maintenance polishing.
Areas subject to heat should be wax and lacquer free.
Antiques and museum pieces should be waxed with pH-neutral wax to protect them.
Lacquers and clear coats discolour with age most of them detract from the finish immediately. They also tend to crack and become porous, thus allowing oxidation to start again.
All Metal Polishes Can Be Used On Components Subjected To Heat
Most metal polishes cannot be used on turbochargers, manifolds, cam casings and similar components. They go grey once they get hot, especially on exhaust pipes.
Only use a polish formulated for this type of application that contains a high melting point wax.
Surface Protection With Carnauba Wax Last Longer
Sorry, Carnauba is acidic so it will attack whatever is underneath. It is also porous which means it will get oxidation going too. Just as a bonus, it will probably increase pitting on-road vehicles as well. This is because by putting a soft surface over your wheels, tanks or whatever – you are helping to guide the missiles in.
Carnauba is great for show vehicles that are subject to regular re-polishing, and useful for protection from road salt in northern climates, otherwise, leave it off.
Antiques Should Never Be Polished
Not true, an old piece does not necessarily have to be dull and dirty.
Most antique brass, copper and silver came from homes where servants were paid to polish these pieces. Should an item not be polished to a high lustre shine it would inevitably have led to the dismissal of the servant responsible.
So how can one prevent or remove oxidation? Antiques need to be restored and preserved. The aim is to maintain the original or factory-delivered condition. Therefore where applicable they need to be polished carefully, then protected by a museum-quality wax and placed into a clean environment where they will not be handled.
Over-polishing is another issue altogether.
A little grime should always be left in the cracks to show antiquity and allow for accurate dating. Always use the finest metal polish possible when dealing with antiques and where cleaning is sufficient that is all that needs to be done. Not too many people will be interested in an old piece of sterling silver or brass if it is blackened with age and tarnished. Polish it with a quality metal polish and finish it with a good wax, it is as simple as that.
If a piece is going to be restored to its original condition, there is nothing wrong with that, because you are adding to its beauty, but there are items that should never be polished. Old tools in particular, normally do better in a used condition and so are not generally restored. Black pewter is not normally restored. However with copper, if it is left to go green, it will slowly erode. Polish it, wax it, and it will virtually last forever.
Gold Metal Polish Can Be Used On Chromium
Sorry – it will not touch it.
If the polish is a true jeweller´s rouge, it will not touch chromium, stainless steel or any hard metal unless you are prepared to sit there for many an hour. Finishing with it is another matter entirely.
Green Rouge & White Rouge Are Similar To Jeweller´s Rouge
Irrespective of what other people tell you, there is no such thing as green or white rouge. Many manufacturers in the industry do not appreciate this, they call anything in a bar jeweller´s rouge – but rouge is French for red and jeweller´s rouge is red because it contains ferric oxide. If it does not contain ferric oxide, it is not rouge. Jeweller´s rouge was developed not just because of how fine it can be, but also because it stains the gold and gives it a sunny glow. Green and white rouge, as many people call them, are abrasive compounds, which are in most cases far too coarse to be used on gold or anything else of value. A good quality jeweller´s rouge is around three times the price of any other compound. Some abrasives are as fine as jeweller´s rouge and finer, but they do not behave like jeweller´s rouge, and jeweller´s rouge they are not.
Because of this generalisation, we have seen very aggressive abrasive compounds being sold as products suitable for jewellery and precious metals. Not good!
All Abrasives Are Aluminium Oxide
Not true, but many people within the trade believe this to be true.
Aluminium oxide is the most popular abrasive around today, next to silica. Still, abrasives can be and are made from just about anything that will scratch and shine metals or plastics. They are made from chromium oxide, aluminium silicate, zirconium silicate, carbides, diamonds, garnets, plastics and all sorts of exciting and sometimes oddball materials.
Regular Polishing Is The Best Way To Protect
Not true, occasional and rare polishing is the best way to protect.
A museum-quality polish is not only very tame as an abrasive, but it also gives a long enduring finish. This keeps polishing to a minimum, so if dusting or cleaning is sufficient to maintain a finish, then that is all that is necessary. A museum polish should contain a pH-neutral wax if it contains any wax at all. After polishing, maintaining the finish should be achievable by occasional cleaning with museum wax.
The use of abrasives in a museum or on antiques needs to be rare and minimal.
Polishing In The Sun Is Fun
Polishing in the sun is certainly fun, but it is also hard work. Everything sets so fast it is just plain old-fashioned hard work, slower, but it is a fine way to get a sun tan.
Lacquered Or Clear Coated Surfaces Are Easier To Maintain
For the short term, the answer is most definitely yes but in the long term, lacquered and clear-coated surfaces are a devil of a job to re-polish and can get quite ugly.
In the marine environment, lacquer or a clear coat is a must on anything but stainless steel. However, in an antique or museum environment clear coats are problematic. Using a museum-quality product keeps re-polishing down to a minimum. When re-polishing becomes necessary, even then it is a very easy process that involves minimal material removal.
Fine Polishes Do Not Cut
Yes and no, because the ability for a compound or polish or cut depends on the shape of its crystals or particles.
What is governed by its size is how deep it can gouge.
Coarse grit may be fairly round and spiky, which will tumble rather than cut. Many abrasives have wedge-shaped edges protruding from triangular-looking crystals. These slice easily, but they can also dig into the surface. However, a big round crystal that tumbles will not have a deep scratch. So the size of the crystal can be as important as the shape.
Coarse grit using one type of abrasive may be a finer cut than many finer grades even if it is the same type of abrasive. The manufacture and how the crystals that form the abrasive are cultivated define its shape and cutting ability or scratch.
A Hard Compound Cuts Better Than A Soft Compound
Yes and no, because the shape of the abrasive crystal also determines how it will cut.
A hard compound or abrasive may also be brittle. It will cut once, lose its edge and will not then cut at all, while a softer abrasive may hold its edge and keeps on cutting.
A Polish That Is Good On Chromium Will Be Good On Stainless Steel And Vice Versa
This will depend on what is in the polish.
There are ways of highlighting the components of metal and chromium is an ingredient of stainless steel It is the chromium that gives stainless steel its shine. Some polishes are great on both, but many only excel on one or the other.
Brass, Bronze & Copper Polishes Are All The Same
Copper is relatively soft compared to bronze and brass, so it should be treated more gently.
Some bronzes can be very hard, and the oxidation that settles on bronze most definitely is very hard.
Stainless Steel Does Not Rust, Oxidize or Stain
A complete misconception is that stainless steel will not tarnish, stain or discolour easily. Austenitic stainless steel will stain, especially if it is overheated or allowed to come into contact with ordinary carbon steel. All stainless steel takes on bleed marks and stains from other metals easily.
All Metals Can Be Polished
Yes, but not to make them shine.
Some manufacturers claim they have a magnesium and aluminium polish. Well, magnesium does not shine, not bright anyway. Because magnesium is a white metal you can clean it and remove oxidation, but you cannot polish it. In magnesium alloys, it depends on the amount of magnesium content determines how well it shines.
Is It Safe To Be Exposed To Environmentally Safe & Low Toxicity Polishes
Yes, no and maybe.
Environmentally safe polishes may use mild acids that occur naturally as active anti-oxidants. However, large quantities of fine metal particulates are not environmentally or physically good, especially soft and heavy metals. Large quantities in the body system through skin absorption and inhalation can have some very serious and long-term effects. Alzheimer´s disease, brittle bones, loss of teeth and skin disorders are just the beginning of a very long list of disorders associated with metals.
Always use barrier creams, face masks and whatever other protection that is necessary to avoid contamination. One of the main problems with environmentally safe polishes is that they are poor performers. For the acids to be of any real use they have to be quite concentrated, then they become not so-environmentally good and often quite harsh skin irritants, so the same rules should be applied to all metal polishes. Another drawback of acid-based polish is that they normally etch into the metal and cause re-oxidation.
Using More Polish Is Best
Many people over-use and flood metal surfaces with polishes believing that they are better protecting the surface. The assumption being the more polish the better the shine and protection, but this assumption is wrong. It is not true that the more polish you use gives a better shine the opposite is true. Using the least amount of polish and allowing the polish to do the work does give better results. It is the grade, size, shape and hardness of the particles that determine how smooth the surface will become and not the volume of the polish used.
More polish creates a smudging problem since fingerprints from human body oils, “dissolve” the solvency of the metal polish. Additionally, too much polish may discolour the surface. Only a trace amount of polish creating a thin film should be applied, rubbing in overlapping circles using only light pressure. Remove the residue in straight lines using a soft clean cloth and buff to obtain a high lustre shine. Repeat until the required surface finish is obtained, and finish by applying one or more layers of microcrystalline wax.
Using more polish does not increase the shine, it only wastes polish and your money. Using less polish gives better results.