US2639226A - Method of staining embossing plates - Google Patents

Description

Patented May 19, 1953 METHOD OF STAINING EMBOSSING PLATES Howard M. Gadbcrry' and Erik Peterson, Kansas City, Mo.,. rated, Kansas Gity, souri.

assignors to Hall Brothers Incorpo- Mo., a. corporation of Mis:-.

N Drawing. Application August 27,, 1951, Serial No. 243,926

3' Claims.

This invention relates. to a metal stain and method of using same in the preparation of em,- bossing plates and more particularly to a solution and its use for staining brass in the wax trans,-

fer of designs in the preparation for-engraving of brass. The transfer is currently made as follows:

The design is scribed on either gelatin or transparent plastic sheeting and dusted and rubbed with tale. The brass plate is prepared by coating it with an asphaltum engravers ground which is essentially bituminous resist. The scribed sheeting is faced against the coated brass and rubbed to transfer the tale to the engravers ground.v The White lines left by this process are again scribed with a point and the brass electrolytically etched in a salt bath or by a, chemical etch until the required lines have been etched into the brass. The asphaltum engravers ground is then removed with thinner and the plate is ready for the engraving process.

The objects of the present invention are to provide a brass stain solution for use in wax: transfer of designs to brass plates in the preparation for engravin same to form embossing plates or dies; to. provide such a brass stain solution which is stable in storage and use; to provide a, stain which will not strike through a wax coating but will provide a stain on uncoated areas which will contrast with the brass so as to be easily visible in fine lines and suficiently durable to resist removal during handling; to provide a stain for brass which is relatively rapid in action, preferably staining the brass in less than one minute, reproducing fine lines and delicate detail; and to provide a brass stain and method of using same with a wax transfer for reduction in time required in transferring a design to a brass'plate.

We have found that salts of certain noble metals are of such character as to be particularly effective in staining uncoated areas of metal plates having surfaces in the active state such as, are. used for engraving of embossing plates or dies, and the salts of noble metals do not penetrate or strike through a transfer Wax coating on such plates. Examples of salts of noble metals having desired staining characteristics are chloroplatinic acid, bromoplatinic acid, platinum tetrachloride, platinum sulphate, chloroauric acid, bromoauric acid, gold chloride, palladium chloride, and palladium sulphate. Certain salts of gold, platinum, and palladium are not useable, notably the cyan-ides such as gold cyanide and the like, which lay down bright gold instead of finely divided black deposits or stain. While these various salts of noble metals are satisfactory, for economy and efficiency we prefer to use gold chloride in the metal stain and process.

The metal stain preferably consists ina solution of gold chloride crystals (AuCLaHClBI-IZO) and distilled water. An example of the proportions of the solution is two (2) grams of gold chloride crystals (AuCIc.I-ICl=.3HzO) and one thousand (1000) cc. distilled water. It is preferred that the proportions of the ingredients used in preparing the solution be kept within plus or minus ten percent (:10 of this example. The solution, mixed in these proportions, preferably should be stored in a tightly stoppered, amber glass bottle or other suitable container until required for use. The solution is light stable, however, andthe solution in use may be kept in a covered glass vessel on the work table without fear of decomposition.

In the actual staining process for brass engraving plates, a rectangular, flat-bottomed glass dish, fitted with a matching glass cover, has been found to be very advantageous for staining by the dipping process. Enough of the brass stain solution should be placed in the staining dish topro videa suitable depth of the solution, for example approximately one-fourth of an inch. The design is scribed on a transparent gelatin o plastic sheeting and the resulting burr around the scribed lines is removed by scraping, usually with the out edge of another plastic sheet. A suitable transfer wax is employed to deposit a wax coating on the transparent plastic sheet everywhere except onthescribed lines. Transfer wax is usually a soft, pliable wax, somewhat softer than beeswax, and in use the transfer wax is warmed between the hands until it is quite pliable and then it is rolled over the surface of the transparent plastic sheet to deposit a thick, dull coating of wax. When a suitable wax coating has been applied to the scribed sheet, the sheet is faced against a polished surface of a clean brass plate and thereverse side of the sheet rubbed with a smooth brushing tool, using considerable pressure. Theback of the scribed sheet is lubricated with a few drops of oil to prevent damage to the sheet. When the plastic sheet is removed from the brass plate, a comparatively uniform coating of wax has been transferred everywhere except where the fine lines had been scribed in the plastic sheet. This application of the wax to the brass plate provides a clean polished surface of the plate exposed in areas corresponding to the design scribed on the plastic sheet and such a clean surface is necessary to obtain the staining of sharp lines and the like on said plate. The brass plate to be stained should be protected by wax coating around the wax transfer and on the four edges. The back need not be wax coated.

To facilitate dipping, a suction cup may be affixed to the back of the brass plate. This allows easy handling of the brass plate so that it can be clipped without wetting the back of the plate and avoids holding the brass plate in the fingers while dipping. The gold chloride solution, while harmless to the hands, will stain the fingers blue near the spot at which they contact the brass, such stain consisting of purplish colloidal gold which is hard to remove.

The coated brass plate is dipped into the staining solution to a suitable depth, for example approximately one-eighth of an inch. Care should be taken not to entrap air under the surface of the brass plate and to obtain good contact with the solution. Approximately fifteen to thirty seconds is required for the deposition of a good black stain in the lines. After the brass plate is removed from the staining solution, the plate should be rinsed with water and the wax coating removed with a suitable solvent.

The concentration of approximately two grams of gold chloride per liter of water is preferred because it gives a good black stain in a reasonable time and the adherence of stain deposited more slowly from weak solutions is better than that of stains deposited quickly in more concentrated solutions. However, as more plates are stained the gold content of the solution will be progressively exhausted and eventually the staining process will require too long to be practical. If the .tip of a clean strip of polished brass does not turn black in the stain solution Within one minute, the solution should be considered exhausted and discarded as the amount of gold lost by discarding such solution will be so slight as to make recovery of it not worthwhile.

The brass plate used for engraving should have a polished surface that is clean and free from grease or dirt before the wax transfer is applied to it. The brass surface should be in the active state, that is, a surface that has been mechanically polished,

The brass stain solution is non-toxic and has no odor. The solution is stable in storage and use and is also economical despite the fact that gold is used therein. When used to stain brass it provides a black stain that reproduces fine lines and delicate detail, with such contrast to the brass surface as to be easily visible. Also the stain is very durable and is not removed by handling during the engraving process.

We have specifically described the process with reference to a metal stain having gold chloride therein, but the same process may be used with stains havin one of the other namedsalts of noble metals therein, as each is capable of use with the wax transfer process to produce sharp lines and good resolution.

What we claim and desire to secure by Letters Patent is:

1. The method of staining designs on brass plates in the preparation for engraving of embossing plates consisting of, scribing a design on a pliable plastic sheet, scraping any burrs from around the scribed lines, applying a transfer wax coating onto the surface of the plastic sheet but not on the scribed lines, placing the wax coated sheet on a polished surface of a brass plate, rubbing the other side of the plastic sheet to transfer the wax coating thereof onto the brass plate except where the design has been scribed in the plastic sheet to leave clean exposed areas of the brass plate corresponding to the design to be reproduced, contacting the wax coated brass plate with a staining solution including a salt of a noble metal selected from the group consisting of chloroplatinic acid, bromoplatinic acid, platinum tetrachloride, platinum sulphate, chloroauric acid, bromoauric acid, gold chloride, palladium chloride and palladium sulphate to stain the exposed areas of the brass plate, and removing the wax coating from the brass plate with a suitable solvent to present a clean surface with the design stained thereon.

2. The method of staining designs on brass plates in the preparation for engraving of embossing plates consisting of, scribing a design on a transparent plastic sheet, scraping any burrs from around the scribed lines, rolling a transfer wax onto the scribed surface of the plastic sheet to deposit a thick wax coating thereon, placing the wax coated sheet on a polished surface of a brass plate, rubbing the other side of the plastic sheet to transfer the wax coating thereof onto the brass plate except where the design has been scribed in the plastic sheet to leave clean exposed areas of the brass plate corresponding to the design to be reproduced, contacting the wax coated brass plate with a staining solution including gold chloride to stain the exposed areas of the brass plate, rinsing the plate with water, and removing the wax coating from the brass plate with a suitable solvent to present a clean surface with the design stained thereon.

3. The method of staining designs on metal plates in the preparation for engraving of embossing plates consisting of, applying a transfer wax coating to a polished surface of a metal plate, said wax coating having cutout portions corresponding to a design to be reproduced to expose corresponding areas of the polished surface of the metal plate, contacting the exposed areas of the polished metal surface with a gold chloride solution to stain said, exposed areas, and removing the wax coatin from the metal plate with a suitable solvent to present a clean surface with the design stained thereon.

HOWARD M. GADBERRY. ERIK PETERSON.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,988,012 Mason Jan. 15, 1935 2,221,641 Knapp Nov 12, 1940 2,448,857 Brice Sept. 7, 1948 2,516,986 Heinse Aug. 1, 1950

Claims (1)

1. THE METHOD OF STAINING DESIGNS ON BRASS PLATES IN THE PREPARATION FOR ENGRAVING OF EMBOSSING PLATES CONSISTING OF, SCRIBING A DESIGN ON A PLIABLE PLASTIC SHEET, SCRAPING ANY BURRS FROM AROUND THE SCRIBED LINES, APPLYING A TRANSFER WAX COATING ONTO THE SURFACE OF THE PLATIC SHEET BUT NOT ON THE SCRIBED LINES, PLACING THE WAX COATED SHEET ON A POLISHED SURFACE OF A BRASS PLATE, RUBBING THE OTHER SIDE OF THE PLASTIC SHEET OF TO TRANSFER THE WAX COATING THEREOF ONTO THE BRASS PLATE EXCEPT WHERE THE DESIGN HAS BEEN SCRIBED IN THE PLASTIC SHEET TO LEAVE CLEAN EXPOSED AREAS OF THE BRASS PLATE CORRESPONDING TO THE DESIGN TO BE REPRODUCED, CONTACTING WAX COATED BRASS PLATE WITH A STAINING SOLUTION INCLUDING A SALT OF A NOBLE METAL SELECTED FROM THE GROUP CONSISTING OF CHLOROPLATINIC ACID, BROMOPLATINIC ACID, PLATINUM TETRACHLORIDE, PLATINUM SULPHATE, CHLOROAURIC ACID, BROMOAURIC ACID, GOLD CHLORIDE, PALLADIUM CHLORIDE AND PALLADIUM SULPHATE TO STAIN THE EXPOSED AREAS OF THE BRASS PLATE, AND REMOVING THE WAX COATING FROM THE BRASS PLATE WITH A SUITABLE SOLVENT TO PRESENT A CLEAN SURFACE WITH THE DESIGN STAINED THEREON.