Cleaning Brass and Copper

Cleaning the metal parts of a lamp made of brass and copper can take some time, depending on how badly these metals have tarnished. Both copper and brass (or bronze) tarnish over time: they gradually turn dark brown to almost black (see Metals in Info Boxes). This layer may have become so thick that the metal underneath cannot even be recognised. The question inevitably arises whether the tarnished surfaces should be cleaned or not. There are very different opinions on this question. For some, tarnished areas are patina, for others they are dirt. To clarify: we are talking about metal parts that have really darkened over time, and not about intentionally applied patina paint that gives bronze statues or zinc castings a completely different colour and a beautiful appearance.

Patina: Yes or No?

There are collectors who regard the tarnished brass or copper parts of a lamp as patina and do not remove them. For these collectors, patina is a sign of antique condition, a valuable distinction that should be preserved if possible. Sometimes it is even literally advertised that the lamp on offer has a beautiful, time-honoured patina. Patina seems to have become a quality feature that increases the value of a lamp (or any other antique) and thus its attraction to those willing to buy. Some of my collector friends also share this view.

Personally, I have a different opinion. I make a very clear distinction between a beautiful, even patina, which gives the lamp a beautiful appearance, and a spotty, unevenly tarnished metal surface, which even appears downright "dirty" as a result, even if it is clean. For me, there is patina worth preserving, which in no way disturbs the appearance of the lamp, and tarnished parts, which give the lamp a dirty, unworthy appearance.

Here I give my very personal opinion about it, without wanting to present it as the only correct one. The metal parts of a lamp are not designed and made to look really brownish black later. Otherwise, one would not apply a protective lacquer to protect such surfaces from tarnishing (see also below). For me, the brass and copper parts are most beautiful when they shine in their original colour. Tarnish layers first start as a golden (brass) and reddish-brown (copper) discolouration of the metal. This discolouration does not detract from the lustre. In this initial stage, the tarnishing is not at all disturbing. Only when it progresses further and the discolouration becomes darker and duller do the metal parts lose their beauty; they become matt, dull, quite dark and look dirty. This has nothing to do with "vintage" or "antique", as it is not an ageing process, but a reaction of the metal with atmospheric oxygen and sulphur. Old objects do not need this layer to be recognised as really old; you can recognise their age even when they are completely clean. A lamp does not only become old and valuable when its metal parts only look tarnished black. I am quite consistent in my opinion and remove what I consider to be ugly tarnish layers from metal surfaces so that the lamp shines anew in all its original beauty, and - as I feel - in its dignity.

On the other hand, it is quite different if the tarnished surface has become very uniformly dark and can even be polished to a high gloss with very fine steel wool or other polishing agents. Then it is a real pity to remove such layers.

There are some lamps in my collection whose metal parts have acquired such a beautiful patina that I only needed to polish them. I have put together four of them in the next photo.

Four examples of outstanding patina
Left: A plinth part made of cast brass in dark patina (L.322)
Middle: A base and figure made of cast zinc in original bronzing (L.120)
Right, top: A hippocamp statue (possibly bronze) in light patina (L.340)
Right, bottom: A cast iron plinth in original bronzing (L.142)

Cleaning Tarnished Metal Parts

To clean such tarnished metal surfaces, the tarnish layer must be removed or abraded. Normal detergents or solvents such as acetone cannot remove this layer at all. There are two different procedures, depending on whether you want to clean smooth surfaces or parts in relief, such as pedestals made of ornamental cast brass:

a) Smooth surfaces: If possible, the original shine should be restored on smooth surfaces without large depressions and bumps. The only thing that helps here is a commercially available brass polish. I like to use the tubes of Mellerud^® polishing paste; you can buy them in DIY stores and drugstores (in Germany). The creamy polish is applied to the surface to be cleaned and rubbed intensively with a cloth until the blackened layer is removed and the metal is revealed. The agent contains chemicals that dissolve the tarnished layer and finely distributed, tiny solids that perform the function of an extremely fine emery paper. Depending on the amount of tarnish, this procedure may have to be repeated several times. In the process, the rubbed fabric turns from greenish/brownish at the beginning to deep black when the tarnish layer is already well worn away. I prefer to work on smaller areas of 4-5 cm. Adjacent areas are worked overlapping so that the cleaning can be done homogeneously and covering the whole area.

Afterwards, the entire surface is freed from cleaning agent residues with a clean, soft cloth by rubbing it vigorously several times and polished to a shine. I always prefer a terry cloth towel for this purpose, as the terry cloth loops can also reach into the fine recesses of the embossed or punched metal surface and remove cleaning agent residues completely. Otherwise, cleaning agent residues left in the recesses turn light green when they dry and do not look very nice. The metal surface cleaned and polished in this way shines with an almost flawless lustre. The welding work rewards you with a beautifully shining surface.

Another very effective tool is steel wool of the second finest grade (marked 000, available in DIY stores or on the Internet). With this steel wool, you can remove many impurities from almost all surfaces made of metal, glass, porcelain, glazed ceramics, marble, if you handle it carefully. The very finest level (0000) has hardly any rubbing properties and is used for polishing. The coarser levels 0 and 00 are more scratchy and should not be used.

Nickel-plated surfaces do not tarnish; consequently, they only need to be cleaned lightly. But here, too, it is worth cleaning and polishing with brass polish to achieve a beautifully shiny surface.

Metal parts of old lamps are often coated with a protective lacquer to protect the metal from tarnishing. This protective coating is more often found on the high quality British lamps. But these clear lacquers become porous over time due to the effects of atmospheric oxygen and UV radiation. Air can now penetrate through the resulting fine pores and cause the metal to tarnish at these points. Depending on how old the protective lacquer is or how thick it was applied, the partial tarnishing in the form of smaller and larger dark spots can be visually quite disturbing. In this case, cleaning the metal surface will be very laborious, as the protective lacquer must first be removed.

There are special solvents that can be used to dissolve and remove this lacquer; however, they are not offered in DIY stores, and as a chemist I also advise against their use, because they are hazardous to health when handled improperly by the layman. Here, too, I unflinchingly reach for the brass polish. Their fine abrasive particles first rub off the protective lacquer if you only rub diligently. You can tell that a protective lacquer was applied by the fact that the cloth you rub the surface with does not immediately turn blackish, as expected, but only slightly greyish-greenish. Only after removing the protective lacquer does the darker colouring begin; then you know that the bare metal surface has been reached.

Now the question immediately arises whether one should not protect the freshly cleaned and polished metal surface again with a protective lacquer? You can do that if you want to. There are sprays for this (for example "Zaponlack"; even better would be non-glossy "fixatives" and "varnishes" for watercolours and pastels). However, I doubt whether everyone will succeed in applying the spray varnish well and evenly in a homogeneous, thin film. That is purely a matter of practice. You tend to spray more, resulting in a thicker layer of paint that you can now even see. In the worst case, you even create drops that run down. Personally, I don't use protective lacquer. I like the open metal surface. I take it upon myself to clean the lamp again after a few years when the metal starts to tarnish more.

b) Parts in relief: In the case of strongly "modelled" parts with a lot of relief, for example the plinth parts made of ornamentally cast brass, manual rubbing with a cloth rag does not help very well; you can only remove tarnish from the outermost raised parts with it, the remaining, deeper areas are not reached, because the finger can only exert pressure on the raised parts. The result is not very satisfactory, as larger areas are still left blackened: The appearance is still quite dark. Here I often use the plastic sanding attachments and sanding brushes from Dremel^®. They come in two suitable shapes and each in three different sanding grades: fine, medium and coarse. I like to work with medium and fine attachments because they scratch the metal surface less. The thin abrasive brushes have a much longer service life, i.e. they wear out very slowly. One must know here: In contrast to the creamy cleaning agent, these abrasive attachments attack the metal somewhat; they remove the tarnished layers very effectively and quickly, but leave behind a somewhat duller metal surface due to fine and minute scratches. To remove these fine scratches, I take steel wool and rub vigorously over the cleaned surfaces. The steel wool smoothes the scratched areas so that the metal shines beautifully again. However, this shine is still somewhat duller compared to surfaces that have only been cleaned with the creamy cleaning agent. But this is not disturbing, because here you don't see large, flat surfaces, but strongly deformed, ondulated, jagged parts. These abrasive attachments are therefore not suitable for cleaning the bare, smooth surfaces of brass or copper sheet.

Grinding attachments and cut-off wheels
Top: Left: thin abrasive brushes; right: abrasive attachments with abrasive foam (each fine, medium and coarse) from Dremel^®
Below: Left: thin and wide flap discs; right: fine cut-off wheels from Proxxon^®

The advantage of this type of cleaning is that the deepest parts cannot be reached even by these sanding attachments. This is especially true for the wide abrasive foam attachments. As these attachments are quite wide, they cannot reach all the small recesses. This leaves deep, narrow "valleys" with their black colouring, and this results in a sculptured, interesting, lively appearance that you would never get if you removed everything that had become tarnished. The thin abrasive brushes, on the other hand, can reach almost every recess, if that's what you're after. In this case, you have to be careful when sanding and only clean the areas that you want to get clean and avoid other areas that should keep their darker colour. You can determine the depth of cleaning yourself by carrying out the procedure more or less carefully and with more or less pressure.

The result of this approach can be seen very well in the pictures in the next photo. These four lamps are made of brass and copper. When I bought them, they were pitifully tarnished and completely filthy. After cleaning them with the methods described above, they show their full beauty; the sculptured figures and ornamental parts stand out vividly against a dark background. Here I dared to experiment: I painted over the non-modelled background uniformly in dark shades to make the figures stand out even more. I used Revell^® paints (matt and semi-matt), which are actually used in model making (available in specialist model making shops or in paint shops).

Brass and copper lamps in detail-shots, each before and after processing
(Top row: details in original found condition; bottom row: after cleaning and processing)
From left: Former Moderator lamp, vase of embossed sheet brass (L.140)
Former Moderator lamp of embossed brass sheet (L.128)
Lamp in openwork cast brass (L.171)
Former Moderator lamp, vase of embossed copper sheet (L.157)

Removing the Tarnish Layer with Acid

A completely different way to remove tarnish from tarnished metal surfaces is to treat them with acids. The dark red copper oxides that have formed on the brass surface over time dissolve very well in acids. You can soak tarnished brass or copper pieces in very weakly concentrated acids for a few minutes. Depending on the thickness of the tarnish layer, the duration of action must be very precise, because acids dissolve not only the tarnish layers but also the brass surface underneath very well. Since the zinc atoms of the brass are first dissolved by the acids, the brass surface is depleted of zinc and the remaining copper atoms colour the surface a tidy red. Later, this red layer has to be laboriously sanded off again until the yellow brass colour appears.

The problem with acid treatment is that you cannot see in the acid bath to what extent the tarnished layer has already been dissolved, because even when dissolved, this layer still adheres to the surface. It can only be removed from the surface with a brush. This makes visual inspection quite difficult. One has to observe the progress of the procedure with constant brushing.

A second problem is caused by the nature of the acid treatment: Every acid attack on the metals leaves fine to very fine pores, which later tarnish again all the more quickly, as the metal surface now offers more surface for the air to attack.

For these reasons and also because working with acids can be quite dangerous for the inexperienced, I advise against cleaning with acids.

Cleaning the Burner

The kerosene/paraffin burner is always made of brass. There are burners that have been nickel-plated, copper-plated or even silver-plated. Nickel does not tarnish; it only becomes slightly dull or matt with time due to dirt. Silver, brass and copper, on the other hand, tarnish heavily (if they are not protected by a protective lacquer) and must be cleaned.

However, one should first separate the basket and gallery from the wick tube. Sometimes this is not possible; the kerosene/paraffin vapours have run into the thread and become really gummy there over time, so that the parts cannot be unscrewed. When this happens, I soak the whole burner in acetone overnight, as acetone is a very good solvent for resinified kerosene/paraffin.

Sometimes you get a very dirty burner with the lamp you bought. Dust has got in and settled over decades; kerosene/paraffin residues have congealed into a sticky mass so that not even the wick can be removed; the inside of the gallery has mutated into an insect graveyard; the holes of the basket are thickly smeared from previous attempts at cleaning with polishing paste, etc. Such a burner urgently needs a cleaning bath in soda. Soda ash is sodium carbonate (not to be confused with caustic soda, which is sodium hydroxide); a mildly alkaline cure-all for many kitchen and bathroom cleaning procedures, and available at any drugstore. I fill a discarded saucepan with enough water to cover the burner (or several burners if necessary) to the thickness of a finger, and I add about two tablespoons of soda. I let the whole thing boil bubbly for about 10 minutes. The dissolved dirt will turn the water brown to dark brown during this time. I then wash the burner under running water while scrubbing all accessible parts clean with a discarded toothbrush. It has even happened many times that after boiling in soda the basket could be separated from the wick tube.

In very stubborn cases, that sometimes doesn't help either. Then I resort to the last resort and heat the seized threaded part of the burner on the pointed and very hot flame of a Bunsen burner (e.g. a small hand burner for superficial caramelisation of sugar in the kitchen) for a few minutes (attention: wear thick kitchen gloves or better gardening gloves, as the metal gets very hot), and turn it constantly to achieve an even distribution of the heat within the thread. The heat makes the solid resin somewhat liquid again, and with some force you can unscrew the wick tube from the basket. Needless to say, the wick (if there was one in the burner) must be removed before this work. However, heating the thread with a Bunsen burner must be done with care. Several parts of the burner are connected to each other by soldering; by heating very strongly, the solder becomes liquid again and can drip away! If the basket cannot be unscrewed even with this measure, then it should be left on as far as possible; trying to turn it too hard always ends in twisting, denting or even tearing the basket!

The bath in acetone also has another advantage: other resinous, encrusted kerosene/paraffin residues in the remotest corners of the burner are also loosened by this.

I clean the brass surface of the burner as follows: I try to clean the flat surfaces on the wick tube and the wick knob ring with steel wool and brass polish to completely preserve the shine here. On the basket, the steel wool is the better choice; the creamy cleaning agent penetrates too much through the punched holes. The prongs of the gallery are better cleaned with the finest Dremel^® abrasive brush and then carefully polished further with fine steel wool.

The more you work on metal surfaces of different embossing with these different methods, the more you get a feel for it and can reach for the most suitable agent much more confidently.