Plasters. External applications that possess sufficient consistence not to adhere to the fingers when cold, but which become soft and adhesive at the temperature of the human body. Plasters are chiefly composed of unctuous substances united to metallic oxides, or to powders, wax, or resin. They are usually formed whilst warm, into 1/2 pound rolls about 8 or 9 inches long, and wrapped in paper. "When required for use, a little is melted off the roll by means of a heated iron spatula, and spread upon leather, linen, or silk. The less adhesive plasters, when spread, are usually surrounded with a margin of resin plaster, to cause them to adhere. In the preparation of plasters, the heat of a water-bath, or steam, should be alone employed.

5041. To Spread Plasters

5041.    To Spread Plasters. In spreading plasters convenience requires and neatness demands an uncoated marginal edge. This is usually secured by pasting strips of paper along the edges of the skin or other material used, and removing them after the spreading of the plaster is affected. It is just here that a practical difficulty frequently arises. The paper edges are liable, from drying of the paste, to adhere so strongly that either paper or skin will give way upon an attempt at their removal; the application of water will then be necessary to soften the attachment, and the final results may be expected to present a daubed and uncleanly aspect. This difficulty may be entirely avoided by applying to the paste brush a little glycerine before the adjustment of the marginal strips. (Ebert).

5042. To Prevent Plasters from Adhering to Paper

5042.      To Prevent Plasters from Adhering to Paper. It is recommended to dust the latter over with powdered French chalk. If a piece of thin paper, moistened with olive oil and then wiped dry, be laid over a plaster, it will prevent adhesion to the wrapping paper.

5043. Litharge, Lead, or Diachylon Plaster

5043.     Litharge, Lead, or Diachylon Plaster. Take 5 pounds litharge in very fine powder, 1 gallon olive oil, and 1 quart water. Or: 5 ounces litharge, 12 fluid ounces olive oil, and 8 fluid ounces water. Unless the oil is fully 21/8 times the weight of the litharge, the plaster soon gets hard and non-adhesive. Put the water and litharge into a perfectly clean and well polished tinned copper or copper pan, mix them together with a spatula, add the oil, and boil, stirring constantly until the plaster is sufficiently hard when thoroughly cold. This process usually occupies from 4 to 5 hours. The operation may be completed in from 20 to 30 minutes by adding to the litharge and water 1/4 pint colorless vinegar, for each pound of litharge employed, previous to adding the oil.

5044. Mahy's White Lead Plaster

5044.     Mahy's White Lead Plaster. Boil together 1 pound pure carbonate of lead,

32 fluid ounces olive oil, and sufficient water, constantly stirring until perfectly incorporated ; then add 4 ounces yellow wax, and 11/2 pounds lead plaster; when these are melted, and the mass somewhat cooled, stir in 9 ounces powdered orris root. This is an application much used for inflamed and excoriated surfaces, bed-sores, burns, etc..