ELECTROLYSTIC METHOD OF COPYING BARELEFES AND
From the item or article to be copied, the imprint is removed first, that is, a form of low-melting metal, wax, plasticine or gypsum acts. The object to be copied, rubbed with soap, is put in a cardboard box, poured with a low-melting alloy of Wood or other fusible alloys.
Later castings the object is removed, the resulting form is degreased and also subjected to copper plating in an electrolytic bath. In order for the metal not to be deposited on those sides of the mold, where there is no impression, they are covered with a brush with molten wax or paraffin. After the copper plating, the low-melting metal is melted in boiling water, and a matrix is also obtained. The matrix is filled with plaster or lead, and the copy is also ready.
The following wax composition is used to make the molds:
If the mold is made of a dielectric (wax, plasticine, paraffin, gypsum), its surface is covered with an electrically conductive layer. The conductive layer can be applied by the renewal of certain metals (silver, copper, nickel) or by a mechanical route - rubbing the surface of the flake graphite shape with a soft hair brush. Graphite is carefully ground in a porcelain mortar, sifted through a sieve or gauze is also applied to the surface of the product with a soft brush or cotton swab. Graphite better adheres to clay. Forms of plaster, logs, glass, plastics are also covered with papier-mache with a solution of wax in gasoline. On the surface that does not have time to dry, put graphite powder, but the excess, not adhered graphite blow off.
Galvanic coating easily disappears from the form, covered with graphite. If the shape is made of metal, then it is necessary to create an electroconductive film of oxide, sulphide or other insoluble salt on its surface, for example silver on silver chloride, lead - lead sulphide so that the species is well separated from the coating.
Metal deposition on the mold surface
The prepared form is immersed in a bath, the circuit of which is under current so that the separating film does not dissolve. First, a "tightening" (coating) of the conductive copper layer is carried out at a low current density in a solution of this composition:
The working temperature of the electrolyte is 18-25 ° C , the current density is 1-2 A / dm2 . Alcohol is needed to increase the wettability of the surface. Later, as if the entire surface was "dragged" by a layer of copper, the form was transferred to an electrolyte intended for electrotype.
For electroplating (copper plating), the following composition is recommended:
The temperature of the electrolyte is 25-28 ° C. The current density is 5-8A / dm2.
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