HU200618B - Process for painting plates, iccasionally embossed plates of silver-content higher than 80 % - Google Patents

Abstract

The surface of silver plates is deoxidised and degreased prior to application of coloured dye comprising 3-8 % alkaline metal sulphide (K or Na), the colour is then rinsed off with water. The wet surface is then heated till the required colour appears. A coat of clear varnish can be applied to the coloured surface.

Description

The present invention relates to a process for coloring plates with silver content greater than 80%, optionally embossed, which is preferably used in the manufacture of applied arts products. In the coloring process of the present invention, the surface to be stained on a silver-containing plate having a content greater than 80% is deoxidized and degreased, if necessary, using an aqueous solution containing an alkali metal sulfide.

A known method for the detection of sulfur is the hepar reaction, which consists of producing a black spot on a bright silver plate when the solution to be examined, when it contains a sulphide ion. The chemical composition of the black spot is silver sulfide.

It is also known that an aqueous solution of sulfur liver (hepar sulfuris) is used for dark pickling of precious metals. Sulfur liver is a mixture of potassium polysulphides, potassium sulphate and potassium thiosulphate. The surface to be picked produces the corresponding noble metal sulphide, which is a very dark black color.

It is also known that an aqueous solution of sulfur liver, which is strongly alkaline, decomposes slowly at room temperature and releases sulfur from the solution.

In addition, conventional methods of coloring silver or high silver content plates are known in which a layer of dye is applied to the surface to be colored and applied thereto. For example, a preferred coloring process is the application of an enamel layer and its anchoring. The disadvantage of these methods is that the presence of the coloring layer in addition to the silver surface in most cases disrupts the uniformity of the surface, resulting in an aesthetically unfavorable, disharmonic impression.

The need for tinting of plates with a silver content of more than 80%, optionally embossed silver plates, necessitated the development of a process which allows the production of a tinted silver surface of a color other than darkness, while harmoniously matching the tinted surface and the unpainted surface. fit.

In our experiments, it has been found that only a partial darkening of the known sulfur liver solution and the heat treatment of the plates can produce a color other than dark on the surface of the silver plates.

Thus, in the process of staining the plates of the present invention having a silver content greater than 80%, optionally embossed plates, the surface to be stained is deoxidized and degreased as necessary, using an aqueous alkali metal sulphide solution. The process consists in wetting the surface of the plate to be colored with a solution of an alkali metal sulfide, preferably potassium sulfide and / or sodium sulfide in a concentration of 0.5-30% by weight, preferably 3-8% by weight, and then wetting the alkali metal sulfide solution with The surface is removed by rinsing with water and the heat is applied locally to the wet surface, which is maintained until the desired discolouration occurs and, if desired, the discolored surface is coated with a colorless varnish.

In carrying out the process of the present invention, a variety of colored discolourations occur during the heat treatment, starting with a straw yellow discolouration, which, when expanded in concentric circles, dissipate on the surface of the disc while a new discoloration appears in the center of the circles. The discoloration changes until the moisture ceases, or the discoloration state at the time of cessation is maintained by cessation of heat treatment. The colors of the resulting dyes cover practically the entire range of colors, for example, golden yellow, green, turquoise, steel blue, magenta, tan, violet. The resulting discolored surface portions retain their color and can only be "wiped" by continuous heating at about 800 ° C.

Discoloration and discoloration of the process of the present invention is the result of the formation of compounds on the surface of the plate by the formation of a small amount of residual silver, alloying and contaminating metals, and complex reduction and oxidation processes between sulfur, sulfide, hydrogen sulfide and water. as well as the appearance of new compounds resulting from the thermal transformation of these compounds.

In a preferred embodiment, the plate is heated to a temperature of up to 50 ° C prior to wetting.

It is very advantageous to carry out the process using a solution of an alkali metal sulfide as a sulfur liver solution.

In a preferred embodiment, the wetting of the surface to be colored is performed by immersing the plate in a solution containing an alkali metal sulphide.

The local heat treatment of the sheet is preferably carried out for up to 5 minutes at each heat treatment site and / or the surface of the sheet subjected to a single local heat treatment is heated to a maximum of 100 ° C.

The main advantage of the process according to the invention is that it produces a surface with a coloration which gives the impression of a silky, glossy and aesthetically harmonious color. Furthermore, it has the great advantage that the process can be carried out extremely fast and with a high productivity compared to conventional coloring processes. A particularly preferred field of application of the process according to the invention is the production of applied arts products and alloy products.

Example I

The invention is illustrated by the following example. The 6 x 10 cm 0.1 mm thick embossed color silver plate is removed from the surface and degreased. The degreased plate was placed in 5% sulfur liver solution and moved in solution for 60 s. The plate is then removed from the solution and rinsed with running water. The plate, which has been rinsed with a wet surface, is fixed and scanned with the torch of a soldering gun, while maintaining heat transfer to the ignition flame at each site until the desired coloration appears there, in some cases for 10-20 seconds.

The resulting tinted plate has the following colors: golden yellow, green, turquoise, steel blue, magenta, rusty and violet.

The resulting colored sheet is coated with a colorless varnish, preferably an acrylic lacquer.

Claims (6)

CLAIMS 1. A process for coloring plates having a silver content of greater than 80%, optionally embossed, wherein the surface to be stained is deoxidized and degreased as necessary, wherein the solution comprises an aqueous alkali metal sulfide solution. Wetted by applying a solution of 5 to 30 wt%, preferably 2 to 8 wt% alkali metal sulphide, preferably and / or sodium sulphide, then removing the alkali metal sulphide solution from the wetted surface by rinsing with water and applying a local heat to the wet surface The heat transfer is maintained until the desired coloration appears, and if desired, the colored surface is coated with a colorless varnish. 2. The method of claim 1, wherein the plate is heated to a temperature of up to 50 ° C prior to wetting. 3. The process according to claim 1 or 2, wherein the solution containing the alkali metal sulfide is a sulfur liver solution. 4. A process according to any one of claims 1 to 4, wherein the wetting of the surface to be colored is carried out by immersing the plate in a solution containing an alkali metal sulphide. 5. A method according to any one of claims 1 to 5, wherein the local heat communication is maintained in a single location for up to 5 minutes. 6. A process according to any one of claims 1 to 4, wherein the area of the plate exposed to snow is heated to a temperature of up to 100 ° C during local heat transfer.