A surgical handbook : for the use of students, practitioners, house-surgeons, and dressers / by Francis M. Caird and Charles W. Cathcart.

  • Caird, Francis Mitchell, 1853-1926
Date:
1889
Catalogue details

Licence: Public Domain Mark

Credit: A surgical handbook : for the use of students, practitioners, house-surgeons, and dressers / by Francis M. Caird and Charles W. Cathcart. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

    252/290 (page 240)
    The only way to prevent air bubhles from loniiinj^ Ijulwcen the mould and Ihc cast is lo pour the phistcr slowly and by inslalinenls into the mould, and to keep constantly shaking and turning the mould round and round all the time. Sometimes it is an advantage to pour the lluid plaster into and out of the mould once or twice, in addition to turning it round and round. If plaster Ije ptnired in without these precautions, air-bells will certainly disfigure thecasi. When the mould is nearly full, a loop of string should be pushed into the plaster to hang the cast by afterwards. (4) Removing the Cast from the Mould.—inalmost llatcasi-., this must be done at the expense of the mould. In all ordinary cast',, only one copy can be made from the original mould. Additional copies can be taken from this by making either an elastic gelatine mould or a plaster piece-mould. The plaster-cast, which has been fdled into the mould, should be set aside for twelve hours. With a chisel and liammer the mould must then be chipped away piece-meal, care being taken not to let the chisel cut into the cast. The advantage of staining the plaster of the mould will now be apparent. It will be found an advantage to begin at the edges, and special care must lie taken of any ]irojecting or thin piece of the cast lest it be broken off with the mould. If the cast is to be painted, one or two coats of boiled linseed oil or of size, as a preliminary, will prevent the paint from being absorbed too quickly by the porous plaster. (a.) A Gelatine Mould is made by suspending the cast, bone, or other object to be copied, in a wooden bo.x large enough to give an interval of at least an inch between the object and all sides of the box. Into this is poured very strong gelatine, or glycerine and gelatine, while hot and lluid. When the moidd is cold, the sides of the box are taken off, and a cut made in the gelatine all round, half way u[) the most prominent parts of the object. After lifting ofl'the top half of the mould, the object can be pulled out of the lower half. The two halves should then be laid together, and a hole cut out of the upper one, opposite its highest point. The sides of the box are now replaced and bound in position, and, in addition, the top of the mould must be held down to prevent the plaster from escaping, leaving, of course, the to]) aperture free. A ]5laster-cast can then be run into this gelatine mould, which, from its flexibility, can be lifted off from the rigid cast without injuring it. {h.) A Picce-MouhV is made of plaster of Paris, and being rigid as well as the cast, must be made of many pieces, each of which can be lifted off without going round a corner. The object to be copieil is first mapped out into areas where casts will lift off; the first area is banked round with clay, the second and succeeding pieces are ranged round the first—blank sides being banked up, and already made pieces being smeared with vaseline lo prevent succeeding ones from sticking to them. When the whole is complete, the inner surface is covered with boiled linseed oil; and the ])ieces having been fitted together are bound with string, and the cast is made through a hole left for the purpose.