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SECTION SEVENTH.

OF MASTICS.

91. Mastics for stopping up holes, leakages, or cracks in Marbles, must not be confounded with those which serve to cement them together, or to consolidate them perfectly; these are used for veneering or pavements. The first is made with gum lac, colored, as nearly as possible, to imitate the Marble upon which it is used. Sometimes the gum is mixed with Marble dust passed through a silken sieve; in other cases, little pieces are used, which are cut and adjusted in the hole or fissure to be repaired, and glued there with the gum mastic-the precaution being first taken to heat the Marble and the pieces, and to take measures for producing a perfect cohesion. The cementing mastics merit the attention of proprietors as well as workmen, because it is often on account of the use of those of inferior quality, that works in cemented pieces deteriorate and lose their value.

92. In the first rank should be placed the thick mastic, composed of two parts wax, three of Burgundy pitch, and eight of resin; melt this, and then throw it into spring water to solidify the paste, then roll it into sticks, and, in using it, melt only such a portion as is needed for your work; this precaution will preserve its strength, as the remainder becomes more brittle by heating it anew.

93. The Corbel mastic, which is used in the seams of the flagging of stairways and terraces, is easily compounded.

Take six parts of the cement of good Burgundy tile without any other mixture, pass it through a silken sieve, add one part of pure white lead, and as much litharge, steep the whole in three parts of linseed oil and one of lard oil, and preserve it in cakes or rolls as the preceding. All the materials used should be thoroughly dry, in order that they may perfectly mix with the oil which unites them.

94. Fountain mastic is compounded of the rubbish of stone ware or of Burgundy tile, amalgamated with thick mastic in such a manner as to form a paste proportioned to the use for which it is required; this is one of the easiest to prepare.

Mastic filings is employed in the same uses as the preceding, as well as in places which are usually damp, or which constantly receive water, as curb-stones, flaggings of kitchens, bath-rooms and water-closets, and stone troughs composed of several pieces, either separate or clasped. This mastic, which is very good when properly used, is composed of a mixture of twenty-six and a half pounds of iron filings, or of iron and copper, such as are found among spur makers, but which must not be rusty, four and a half pounds of salt, and four garlics; this is infused for twenty-four hours into three and a half pints of good vinegar and urine; it is then poured off, and the thick paste which is found at the bottom of the vessel is the mastic, which should be immediately used.

These mastics should be used upon materials which are perfectly dry, otherwise they do not incorporate well, roll up, and are repelled by the moisture. Therefore, in executing this kind of work, the precaution should be taken to choose dry weather, and to open the seams well with a curved, sharp instrument, finally polishing them with a chisel.

Before laying down the mastic, the dust must be removed from the seam by blowing into it with a common bellows; a long, straight, iron chafing dish, closed at the bottom, with the grate elevated about an inch to obtain a current of air, is then passed over the seam; this chafing dish is filled with burning charcoal, the caloric of which draws out the moisture from the stone or Marble.

The slightest dust or the least dampness, hinders the adherence of every mastic; water infiltrates, and, when it does not immediately affect it, it will glide through after the least frost, after which it is impossible to remedy it. It is these infiltrations which cause so many proprietors to object to flaggings and other works of this kind.

95. Dilh mastic is, undoubtedly, the best that is known, but its composition is yet a secret; it is very costly, and its uniform color of a dirty white, renders it unsuitable for many works in Marble, for which reasons it is not much used by Marble workers.

There are others which we do not strongly recommend, because we do not consider them sufficiently tested; we shall point them out, however, that they may be experimented on.

 

MASTIC FOR CEMENTING MARBLES.

96. The Mastic used by Marble workers for gluing and consolidating Marbles is of gum lac, colored. But this mastic, which is applied hot, only produces a strong cohesion when the Marble is also heated, which it is not always easy to do.

No good cold mastic is known to Marble workers, and the discovery of one would render a very great service to their art. The following recipe claims this merit:

 To compound this mastic, take-
 Hydrochlorate of ammonia, 2 parts.
 Flour of sulphur, 1 part.
 Iron filings, 16 parts.

Reduce these substances to a powder, and preserve the mixture in closely stopped vessels. When the cement is used, take twenty-parts of very fine iron filings, add one part of the above powder, mix them together, adding sufficient water to form a manageable paste; this paste, which is used for cementing, solidifies in fifteen days or three weeks, in such a manner as to become as hard as iron.

MASONS' MASTIC FOR COATING THE INSIDE OF
CISTERNS, BASINS, ETC.

97. Pulverized baked bricks, 2 parts.
  Quick lime, 2 parts.
  Wood ashes, 2 parts.

Mix these three substances thoroughly, and dilute them with olive oil. This mastic hardens immediately in the air, and never cracks beneath the water.



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