Copper is a very elegant ductile metal that was used to make furnishing objects, jewelry, vases, pots, stills and cauldrons.
Currently it still finds enormous use for the construction of gutters and profiles around the houses; the characteristic color and resistance over time make it particularly suitable for these external elements of embellishment.
Copper is quite reactive with air and, consequently, tends to change color in a short time. This can be seen more drastically for the copper exposed to the outside, where it will create a brownish oxide layer that will replace the elegance of the polished metal. However, it is precisely the presence of this oxide that keeps the metal intact over time, so there is no problem in leaving the metal "abandoned" as its functionality will not be affected. Depending on the environmental conditions, copper can acquire different oxidative states (cupric oxide, cuprous oxide) or react to form salts (carbonate and copper sulphate) with a typical greenish color.
For those who want to try their hand at cleaning copper, you can use different techniques. Some home procedures are widespread, where the copper object (pans, teapots, vases, etc.) is washed using products easily available in the kitchen. Usually, wine vinegar or lemon juice is used, concentrated or diluted, or mixed with table salt. The salt helps to create friction on the surface and increase the solubility of the copper ions detached from the acid. This process is effective in synergy with mechanical action or if the oxidation is not too advanced, otherwise it would require time and several applications.
external artifacts such as gutters it is necessary to use stronger products,
first of all is muriatic acid (or hydrochloric), available on the market
even at rather high percentages. It is a strong acid and therefore care must be
taken, however it is very fast and allows the removal of heavy oxides. In the
following photos you can see the effectiveness of a single application of
muriatic acid (by spray or soaked rag). It is advisable not to work in the sun
and to rinse after application. Subsequent applications may be necessary to
make the metal more and more shiny. In any case, the surface cleaning of the
gutters is complex, dangerous and not recommended for the private sector.
At the end of the pickling, it would be advisable to treat the copper with special products for the preservation of the surface and to slow down future and inevitable reoxidations. Some well-known commercial products for copper cleaning already contain brightening and polishing raw materials (such as some silica earths) and protectives against oxidation (such as fatty acids, waxes, oils).
Below is a copper cleaning formulation from a famous household cleaning company:
• Sodium alkylbenzenesulphonate: 5-7%
• Sodium hydrogen sulphate: 3-5%
• C9-C11 ethoxylated alcohol: 3-5%
• Sulfamic acid: 2-3%