US 3674484 A
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July 4, 1972 v. SPINSKI PHOTOGRAPHS ON CERAMIC OR CERAMIC-LIKE SURFACES Filed Jan. 28, 1971 Ash Kaolin, Carbonate Q E, A iomic Number 12 -56 Appy Prime Codi 0f V0 loaf/Lie Group Fire Appy jwio Emulsion Expose Emulsion And Process Image Heat/1 b 80E/flour To 1250 15007? P/ZOZO Enlarger INVENTOR Vic for S pinski WWW AT TOE/V1573 United States Patent O 3,674,484 PHOTOGRAPHS ON CERAMIC OR CERAMIC- LIKE SURFACES Victor Spinski, Newark, Del., assignor to University of Delaware Filed Jan. 28, 1971, Ser. No. 110,506 Int. Cl. G03c 7/00 U.S. Cl. 9634 8 Claims ABSTRACT OF THE DISCLOSURE Ceramic objects are conveniently decorated using photographic techniques by first preparing the surface of the object in any conventional manner, for example, by first firing the green object to bisque temperature, allowing the object to cool, washing it with an alkaline solvent, and drying it. To the prepared surface is then applied a priming coat which is generally a mixture of volcanic ash, kaolin, and a water-insoluble carbonate of a Group II element of atomic number 12 to 56 all uniformly dispersed in water. The priming coat is allowed to dry and the object is then fired to bisque temperature around cone 08. Upon cooling, a photographic emulsion containing an image forming component is applied to the coated object under conditions conventional to the photographic art. The object with the now photosensitive surface is then exposed by conventional photographic techniques and processed to develop the image. The entire object is thereafter placed in a furnace and heated at a rate not to exceed 40 F. per hour to 500 F., then at a rate not to exceed 80 F. per hour to from 1250 F. to 1500 F. and then allowed to cool slowly to ambient temperature. The object thus obtained has a glazed black and white silver image of lasting durability.
BACKGROUND OF THE INVENTION This invention relates to a method for applying photosensitive emulsions to refractory surfaces and vitrifying the same without the usual disadvantages that result during firing.
Many of the known methods of decorating ceramic objects require that the various designs and other decorations be applied usually by hand. While hand application is quite adequate for making one or two ceramic objects, for commercial scale production this technique is generally not useful, except for objects which command a premium price. For this reason, photographic techniques have been developed which permit mass production of decorated ceramic ware. However, such previously used methods have had limitations with respect to the physical shape of the objects with which they can be used.
The process of this invention overcomes the limitations inherent to previously used methods for producing decorated ceramic objects. For example, intricate, precise designs can be produced using photographic techniques that cannot be produced easily by hand.
It is, therefore, an object of this invention to obviate many of the difiiculties encountered which firing silver images produced from gelatine-silver halide emulsions presents.
Another object of this invention is to provide a simplified but improved method of applying designs to ceramic objects.
A further object of this invention is to provide a photographic method for decorating ceramic ware with permanent vitrified images on refractory surfaces.
The usual photographic emulsion is a gelatine-silver halide emulsion. Unfortunately, many have experienced difficulty when using such emulsions since as noted by Avery in his U.S. Pat. No. 3,341,327 issued Sept. 12, 1967,
3,674,484 Patented July 4, 1972 the silver images deteriorate to a dirty, brownish stain which is nearly indistinguishable when fired to temperatures in the range of 1400 F.
Other problems encountered when firing normal gelatine-silver halide emulsions are noted in a second Avery U.S. Pat. No. 3,406,066 issued Oct. 15, 1968. These problems include contracting, stretching, blistering, tearing and frilling of the emulsion layer. The carbonaceous ash residue formed during firing is designated as the cause of these problems by Avery who proposes to alleviate the problems by increasing the proportion of silver in the emulsion. While this often results in some improvement, little is done to improve or enhance the background or surface on which the image is formed. Further, this approach is relatively expensive particularly with the increasing prices of silver.
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT In a preferred embodiment of this invention, a design is applied to the surface of a ceramic object, such as an article of china, porcelain or pottery by first coating the object, when in bisque condition, with an engobe of volcanic ash, residual clay, and a carbonate of an element of Group II of the Periodic Table of atomic number 12 to 56. The thus coated object is fired to bisque temperature, allowed to cool to ambient temperature, a photographic emulsion containing an image forming component is applied to the coated surface and allowed to dry. Next the photographic emulsion is exposed to an image and developed and fixed by conventional photographic techniques, and the object with the image developed thereon is heated to vitrify the surface and fix the image. Generally, the heating step is effected in tWo steps: first, at a rate not to exceed 40 F. per hour to a temperature of approximately 500 F. and then at a rate not exceeding F. per hour to a temperature between 1200" F. and 1500 F. The object thus obtained has a true silver image developed thereon, which is of high quality, black color, with sharply defined edges. The image is sharp and substantially free of peeling, blistering, contraction, stretching, tearing, or frilling as encountered in the prior art as described by Avery.
BRIEF DESCRIPTION OF THE DRAW ENGS The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will be best understood from the following description when read in connection with the accompanying drawings, in which:
FIG. 1 is a process block flow diagram setting forth the steps of the process of this invention;
FIG. 2 is a typical ceramic object such as a vase in the process of having a photographic image applied thereto for subsequent vitrification; and
FIG. 3 is a fragmentary cross-sectional view of the object of FIG. 2, showing the object with coatings applied in accordance with the methods of this invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT The process or method of this invention may be most easily described with reference to FIGS. 1, 2 and 3. In order to apply the photographic emulsion, for the purpose of forming a design or other image to a ceramic object or ware 10, a base or priming coat 12 is first applied. Thereafter a gelatine-silver halide photosensitive emulsion 14 is applied to the priming coat 12, dried, exposed to an image, the image developed on the surface by conventional photographic techniques, fixed, and the object with the image thereon is fired.
Initially, if the ceramic object is in the green state, it is first fired to bisque temperature which is usually in the range of 1900 F. After the baking or firing of the ceramic object, such that it is now in bisque condition, the object 10 is allowed to cool, washed with a suitable alkaline solvent, such as washing soda, to remove any grease that may be on the surface due to handling, and allowed to dry.
Next, the clean ceramic object 10 is given the coating 12 which is an engobe consisting of from 1 to 1.2 parts by weight of volcanic ash, 1.00 to 0.80 part by weight of residual clay and 1 part by weight of a heat labile or preferably a carbonate salt of a Group II element of the Periodic Table of atomic number 12 to 56 [see General Chemistry, a Systematic Approach, Sec. Ed., page 116, The Macmillan Co., New York (1960)], dispersed in water, the parts by weight being based on the total weight of the solid components. The amount of water required is that which is compatible with the method used in producing the smooth dispersion. This coating may be applied by any of the known methods such as brushing, dipping, pouring, or spraying. The thin layer or coating thus obtained forms a suitable base for subsequent application of the photographic emulsion and since it contains both pigment and filler it functions both as a sealer and a primer coat. The preferred coating is one consisting of equal parts by weight of the three elements together uniformly dispersed in water in amounts sufiicient to produce a free flowing, smooth dispersion to permit its application to the object 10.
Volcanic ash, as is known, has relatively uniform properties regardless of its source. Its chemical composition can vary slightly, but generally it consists essentially of silica, alumina, potash, soda and iron oxide, along with smaller amounts of lime and rutile.
The residual clay component of the priming composition in its raw form is coarse and usually a diflicult material to work with. Residual clays include the so-called china clay, kaolin, and other like clays which produce upon firing a white color. These include bentonite and M & D Ball clay, or low shrinkage bentonite clay.
The preferred heat labile salts are carbonates of the Group II elements of the Periodic Table of atomic num ber 12 to 56 and strontium and calcium carbonates are preferred because of their excellent fiuxing characteristics used in the process of this invention.
The resultant coated objects, regardless of the method of coating employed, is permitted to dry at ambient temperature, and then fired preferably in an oxidizing atmosphere to bisque temperature, usually cone 08, about 1700 F. After the firing the coating is converted to a sharp, white coating which is useful in and of itself and it serves as a high quality background surface for photographic processes as will be described.
Next, a conventional photographic emulsion 14 of the gelatine-silver halide type, or one containing an image forming component such as silver nitrate, is applied to the coated object. One particularly preferred emulsion is prepared as follows:
Dissolve 10 grams of gelatine is 360 cc. warm water using a non-metallic container. Then add 32 grams of potassium bromide ad 0.8 gram of potassium iodide and dissolve. Raise temperature to 131 F. and keep it there. After this, all work must be done in a darkroom with red safe light only. Dissolve 40 grams of silver nitrate in 400 cc. of water. Add this to the potassium bromide solution and stir constantly and evenly. Mix it at about 40 cc. per minute. This process should be completed in 10 minutes. Then stir for 10 minutes more with temperature still at 131 F. Next add 40 grams gelatine to set the emulsion and then cool without stirring until it becomes jellylike. This should take around 3 to 4 hours. When jelled, shred or mash the emulsion through cheesecloth or plastic screening, and pour 3 liters of water into it at room temperature. Let mixture stand for about 3 minutes and then pour the water off. Repeat 5 or 6 times. This is to remove the soluble salts. One can Wash under running water for 15-20 minutes. Drain off all water and heat for 15 minutes at 131 F.; slowly cool to 104 F. and the emulsion is now ready to use by brushing or spraying. The product can be stored for considerable lengths of time in light-tight containers preferably kept under refrigeration.
The photosensitive emulsion used in this invention may contain any silver halide described in U.S. Pat. No. 3,406,- 066, above identified, but there is no need to use the large amounts of silver halide required by Avery. For that matter, any of the silver halides usually employed in photographic emulsions such as silver bromide, silver chloride, silver chlorobromide, silver bromoiodide, or the like, may be used for the radiation sensitive halide.
The photographic emulsion may be applied by brushing, dipping, whirling, spraying or the like. Generally, the portion to be applied is warmed and applied by brushing or spraying onto the desired area. It is allowed to dry, preferably using gentle hot air to effect faster drying. Next the emulsion is exposed to an image. Usually this is most easily accomplished using a photographic enlarger and projecting the image onto the emulsion coating. The image may be of any suitable design, landscape, or for that matter, may contain printed information or any other design which can be recorded on photographic film. A red light filter can be used between the enlarger and the emulsion to position the image so that it is exactly projected onto only the desired area. Once exposed, to actinic radiations, the emulsion is processed in a conventional manner to develop the image to which it was subjected. It is often convenient to pour or sponge the developer onto the exposed emulsion until the image is developed. Pouring or spraying on a conventional developer such as that sold under the trade name Dektol by Eastman Kodak works well, followed by a conventional stop-fix and then washing with warm water. The developed image is then allowed to dry. The coated image-containing object is placed in a furnace and fired. The furnace may be an oxygen furnace.
In the firing step, the object bearing the image is heated, preferably at a rate not to exceed 40 F. per hour until the temperature of approximately 500 F. is reached and thereafter heated at an increased rate not to exceed F. per hour until the temperature in the range of 1250 to 1500 F. is reached. After this the object is allowed to cool slowly within the furnace to ambient temperature and is removed from the furnace. The article thus produced is a silver image having good, solid, clear black features on the white, crisp, background surface provided by the coating. The vitrified image is secure, being bonded tenaciously to the surface. It is not subject to the usual problems encountered with the prior art silver images such as peeling, blistering, contraction, stretching, tearing or frilling.
Although this invention has been described with particular reference to ceramic ware, it is to be understood that the principles of this invention may be applied also to glass plates, metal plates and other similar refractory surfaces. Such surfaces may, by applying this invention, be used not only for decoration but in order to record information in a permanent form. Further, printed circuits and photographic scenes as well as many other applications will be apparent to the user.
It is obvious that many embodiments may be made of this inventive concept and that many modifications may be made in the embodiments hereinbefore described. Therefore, it is to be understood that all descriptive matter herein is to be interpreted merely as illustrative and exemplary and not in a limited sense. It is intended that various modifications which might readily suggest themselves to those skilled in the art be covered by the following claims.
What is claimed is: 1. In a method of forming a vitrified silver image on a ceramic object comprising the steps of:
applying a prime coating to said object, applying a photosensitive silver halide emulsion over said prime coating, image-wise exposing said emulsion to actinic light and developing the emulsion to produce an image, and firing said ceramic object bearing said image to provide a vitrified silver image bonded to said prime coat, the improvement wherein said prime coat is applied by the steps of:
coating said ceramic object with an engobe consisting of a mixture of volcanic ash, residual clay and a carbonate of a Group II element having an atomic number between 12 and 5 6 inclusive, and firing said coated object to bisque temperature to produce a white coating tightly adhering to said object. 2. A method according to claim 1 wherein the proportions said engobe consists of 1.00 part by weight of said carbonate, 1.00 to 0.8 part by weight of said residual clay, 1.00 to 1.2 parts by Weight of volcanic ash.
3. A method according to claim 1 wherein said residual clay is kaolin.
4. A method according to claim 1 wherein said salt is calcium carbonate.
5. A method according to claim 1 wherein said carbonate is strontium carbonote.
6. A method according to claim 1 wherein said image bearing object is fired at a first predetermined rate to a first temperature and then at a second increased rate to a second temperature.
7. A method according to claim 6 wherein said first temperature is about 500 F. and said second temperature is from 1250 F. to 1500" F.
8. A method according to claim 6 wherein said first rate is less than F. per hour and said second rate is less than F. per hour.
References Cited UNITED STATES PATENTS 3,406,066 10/1968 Avery 96-34 3,369,894 2/1968 Yu 9634 3,341,327 9/1967 Avery 96-34 3,171,742 3/1965 Yu 96-34 NORMAN G. TORCHIN, Primary Examiner I. WINKELMAN, Assistant Examiner US. Cl. X.R. 9636.2
3, 7 Dated y 97 Patent No.
Victor Spinski Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Column 3, line 64, "ad" should read and Column 5, lines 19 and 20, cancel "the proportions"; line 25, "salt" should read carbonate Signed and sealed this 7th day of November 1972.
EDWARD M.FLEICHER,JR. ROBERT GOITSCHALK Attesting Officer Commissioner of Patents ORM po'wso (10459) USCOMM-DC 60376-P69 a US. GOVERNMENT PRINTING OFFICE I969 O356-334.