Tin

Tin is a soft white metal found in essentially pure form in some objects such as ingots but is more commonly encountered as plating on food cans. Tin is also a constituent of pewter when alloyed with lead.

In the 19th and 20th centuries tin was combined with a number of other elements to produce a range of alloys used principally for utensils and ornamental ware. Typical examples are Britannia metal (93% tin, 5% antimony, 2% copper) and leadless pewter (alloyed tin).

Britannia metal was developed in England during the mid-1700s in response to the threat to the pewter utensil industry from cheap porcelain. Old pewter was dull and undesirable as a food container because of its lead content. Although the new alloy was brighter and stronger it eventually lost favour as a metal for the production of household utensils.

Deterioration

Although it is normally quite stable, tin reacts slowly with the atmosphere to form grey stannous oxide and finally, stable white stannic oxide.

Many objects made of tin or its alloys are found covered with a dull grey coating of corrosion products. These form a protective patina and unless the corrosion is very pronounced or unsightly, retain this patina where possible.

Preventive Conservation

Observe the general guidelines mentioned at the beginning of this chapter.

Treatments

Cleaning

Although tin objects are quite strong, careless handling will still damage their surfaces. If an object has to be cleaned, try the following regime:

• use a pure soap in warm water to remove dirt and grime;
• rinse with fresh water;
• wipe with methylated spirits; and
• polish with a soft cloth.

For badly deteriorated objects, seek the advice of a conservator.