Cleaning Glass, Ceramics and Porcelain

The glass and ceramic parts (incl. porcelain) should be cleaned with household dishwashing detergents and rinsed clear with water. Immediate drying is advisable, especially in areas with "hard" water, to avoid ugly limescale stains.

Sometimes you get majolica lamps whose majolica lid of the font has a noticeably darker colour than the rest of the vase. This is not dirt, but glaze of the majolica that has darkened over time due to the effect of the kerosene/paraffin. Glazes are sometimes - depending on the chemical composition and firing temperature - quite porous, or covered with hairline cracks that can hardly be seen with the naked eye. Kerosene/paraffin vapours penetrate these pores and cause the colours to darken. This is not a reduction in quality.

Majolica lids darkly tinted with kerosene/paraffin

With some lamps made of glass, ceramics or porcelain, one discovers slightly dull, somewhat dirty-looking surfaces, which are caused by frequently touching the lamp with hands (skin grease!) and other air pollution. These surfaces can be cleaned very well by rubbing them properly with a cloth rag moistened with acetone (available in DIY stores and online shops). Instead of cloth, you can also use paper from a kitchen roll. This will restore the perfect shine to glazed majolica and porcelain surfaces. Before cleaning painted parts of a lamp with acetone, you should test a hidden spot to see if acetone dissolves or smears the colours, because some paintings are not burnt in, but painted with "cold colours" (which, however, is quite rare). See the subchapter Glass at Infoboxes.

Sometimes in the small depressions or along the thickly applied brush strokes of a pasty painting on glass fonts, or in the depressions of strongly reliefed majolica, there is a dark brown, almost blackened and dried-out soiling, which comes about through the mixing of the kerosene/paraffin vapours with the usual air pollution (e.g. dust particles). While in normal cleaning by dusting etc. the raised parts of the painting are continually wiped and cleaned, this soiling remains in the fine recesses and gums up with time, thus becoming solid. This blackish soiling can also be easily dissolved and removed with acetone. For this purpose, I recommend using normal cotton swabs (to wet the depressions generously with acetone) and pointed wooden toothpicks (to remove the softened dirt from the depressions), but never knife tips or other sharp, metal objects. These encrustations may be so stubborn that you have to repeat the cleaning procedure until the recesses are really clean. If you love your lamps, you have to work on them patiently.

Sometimes there is a thin film of dirt on the smooth glass parts of a lamp or on its shade that cannot be removed by normal washing-up liquid. This could be the remains of a sticky label, for example, or some sticky liquid that has dried up. In these cases, you can use acetone as a solvent as well as a silver or brass polish to thoroughly clean such surfaces.

Often glass fonts have stubborn, dark, reddish-brown dirt on the inside from decades of using low-quality, impure kerosene/paraffin that left a resinous residue. This dirt can be easily removed with a few squirts of scrubbing milk (available in drugstores and supermarkets) and an oblong cylindrical brush bent slightly in the middle to reach all corners of the font. Larger incrustations can also be removed with acetone. Cylinder brushes can be bought either in well-stocked DIY stores or from brush dealers. The mail-order company Stuga-Cabaña (see Literature and Sources) also offers them in several sizes. If you don't have a cylindrical brush at hand, you can help yourself with a normal dishwashing brush with an oval head (just fits through the 39.5 mm font collar) or with old toothbrushes for smaller openings. However, you cannot reach all angles with such brushes; you cannot bend them at will.

Cleaning the glass chimneys from the inside also requires a cylinder brush of a suitable size that has been properly wetted and 2-3 squirts of a common dishwashing detergent spread on it. Care should be taken when cleaning the chimneys; especially the older ones are made of thin glass and break easily if you apply strong pressure or use the brush in a tilted manner. The outer surface of the chimney can easily be cleaned with a dishwashing sponge and a few squirts of washing-up liquid. If the chimney has a printed mark, you should not rub vigorously on this mark; the printed white ink will be rubbed off more and more.

Cleaning the Stones

In addition to their glass, ceramic and metal parts, many lamps also have sections made of natural stones such as marble, alabaster, slate or serpentine. These are often column and base parts. Cleaning them is relatively easy, provided they are not made of slate or alabaster. All stones except alabaster are completely resistant to water, commercial washing-up liquids and organic solvents such as acetone. They can be easily cleaned with soapy water and washing-up liquid. Heavier stains should be soaked overnight in soapy water. After cleaning, drying and polishing, marble and serpentine pieces will shine again if there is no external damage. Areas that have become somewhat dull or scratched can even be gently polished with very fine steel wool and then treated with brass polishing cream.

Slate was often used as a stone base for high-end lamps in the past. It is relatively easy to recognise slate when the surface of the stone base is covered with a glossy black lacquer. Slate is relatively soft by nature (therefore easy to grind), grey to anthracite in colour depending on its occurrence and matt to greasy-glossy. Therefore, the slate bases of kerosene/paraffin lamps are always additionally lacquered glossy black. If this surface has become dirty, dull or even damaged, it may be necessary to sand down the entire damaged surface and then paint it again with a suitable black paint (to avoid brush strokes, it is better to use a spray paint). Finely sanded surfaces of slate can also be waxed. I have successfully used the following method for this: I dyed a commercially available furniture wax (e.g. antique wax from Clou^®) black with very fine coal dust and rubbed the slate surface thoroughly with it. Very fine coal dust for artists is available from Boesner GmbH, a rapidly expanding chain of shops for high-quality artists' supplies, now represented by many branches in Germany, Switzerland, Austria and France. The advantage of furniture wax is the possibility of subsequent polishing with a cloth rag, so that a silky glossy surface is created.

With alabaster, on the other hand, I would advise against water-based agents. Alabaster is a naturally occurring calcium sulphate (= gypsum) and is therefore slightly soluble in water. Any treatment with water-based agents will remove a wafer-thin layer from the alabaster surface, leaving a matt appearance. Alabaster is relatively soft and very easy to sand. If the surface of the alabaster is very dirty, I recommend sanding these areas very carefully until the dirty layer has been removed. The abrasive can be very fine sandpaper (600's or even higher in fineness) or finest steel wool. After sanding, the sanded area (or the entire surface that has become dull) should be rubbed with a brass polish (e.g. Centralin^® or Mellerud^®) and then rubbed vigorously dry with a medium-soft cloth. The result is surprisingly good: the alabaster surface shines again!

Acidic cleaning agents such as vinegar cleaner, lemon dishwashing detergent, etc., must not come into contact with marble and alabaster surfaces, because these stones react with every acid (they dissolve in it). What remains are matt-rough surfaces that can only be polished again with difficulty.