The theoretical composition of common pewter is 80 parts tin and 20 of lead; but as the manufacturers consider that a better alloy is formed by melting up old pewter with new ingredients, the composition is uncertain. The French legislature sanctions the use of 82 parts tin and 18 of lead, as forming an alloy which is quite harmless in vessels used for wine and vinegar. Antimony is sometimes added for hardening the tin, and for giving a more silvery colour. Zinc is also used to diminish the oxidation; a small lump of that metal being allowed to float on the fluid pewter during the casting; or the fluid is occasionally stirred with a strip composed of equal parts of zinc and tin. The finest pewter, called tin-and-tempor, consists mostly of tin, with a small proportion of copper, which makes it hard and somewhat sonorous; but the copper is apt to impart a brown colour. The temper is formed by melting the copper, and adding twice its weight of tin, and from ½ lb. to 7 lb. of this alloy is added to each block of tin, which weighs from 360 to 390 lb.

In the year 1772 the Pewters' Company made an attempt to regulate the quality of pewter-wares by establishing "A Table of the Assays of Metal, and of the Weights and Dimensions of the several sorts of Pewter Wares." The assay was directed to be made by casting a small button of the metal, to be tried in a brass mould so proportioned that such a button of pure tin should weigh 182 grains. All the metals added to the tin being heavier than tin, the buttons would be heavier in proportion as they contained less tin. On these data the following scale was founded:

| Assay of pure tin | Grains | |------------------|-------| | Fine or plate metal | 1½ grains heavier than tin, or... | 182 | | Tinning metal | 3½ grains heavier than tin, or... | 184 | | Ley metal | 1½ grains heavier than tin, or... | 186 |

Pewters formed of equal parts tin and lead are about 50 grains heavier than tin, or 232 grains. Such pewters, when cast, are black, shining, and soft; and when turned, are dull and bluish. Pewters which contain only one-fifth or one-sixth of lead, cast into wares which are white, hard, and without gloss; they form a good metal, and are but little darker than tin. The French have published a table of specific gravities for testing the quality of the alloy, the legal standard of which is 7·764. An excess of lead is detected by an increased density.

Of the three ordinary kinds of pewter distinguished in the Pewters' Scale, plate pewter is the hardest, and is used for plates and dishes. The pewter called trifle is used for beer-pots; and ley for the larger wine measures. The best plate pewter is sometimes composed of 100 parts tin, 8 antimony, 2 bismuth, and 2 copper. Trifle consists of 83 of tin, 17 of antimony, and usually a large proportion of lead.

Pewter plates and dishes are formed by hammering, and measures and spoons by casting. The parts are joined together by means of soft solder, assisted by a blast of hot air from a small charcoal furnace. Pewter is also formed into sheets for printing cheap music; the softness of the metal allowing the notes to be formed by means of punches, which is cheaper than engraving with the burin. Laps and polishers of pewter are also formed for the use of lapidaries, jewellers, watchmakers, &c.

Pewter-wares are finished by burnishing with oil, and cleaning off with a rag and whiting. Pewter vessels may be cleaned by means of silver-sand and water, or with a solution of potash or of soda, to remove grease. (c.t.)