WO1999061382A1

WO1999061382A1 - A glass article with a picture of an enamel and a process for producing a glass article with a picture of enamel

Info

Publication number: WO1999061382A1
Application number: PCT/SE1999/000795
Authority: WO
Inventors: Per Sundberg
Original assignee: Orrefors Kosta Boda Ab
Priority date: 1998-05-11
Filing date: 1999-05-11
Publication date: 1999-12-02
Also published as: SE9801627D0; SE9801627L; AU4404199A

Abstract

The manufacture of glass objects that have colour pictures or images embedded in the glass wall, wherein an enamel colour decal is applied to a glass blank. The enamel colour is fused to the surface of the blank and a gather applied thereto. A glass object that has a colour picture or image embedded in the glass wall.

Description

A GLASS ARTICLE WITH A PICTURE OF AN ENAMEL AND A PROCESS FOR PRODUCING A GLASS ARTICLE WITH A PICTURE OF ENAMEL

The invention relates to glass articles or objects that have an enamel picture or image embedded within a glass wall, and a method of producing glass objects that include enamel pictures or images.

Glass objects which have colour pictures or images embedded within the wall of the object are known to the art. DE 286

770 describes a method of producing glass objects in which glass paintings are fused in the wall of the object. The outer wall of a hollow glass body hanging from a glass blowpipe is painted with a colour mixture that contains pigment (oxides) mixed with glass. The fusability of the colour mixture is roughly the same as the fusability of the molten glass used to coat the hollow glass body, or gather.

Subsequent to colouring or painting the hollow glass body, the body is dried and then heated and thereafter coated with a layer of molten glass, by dipping the body in hot, molten glass. The body, or gather, is then blown into its desired shape .

DE 2 160 952 describes a glass product which is produced by pressing or blow-shaping an intermediate body, wherein the process is terminated by press blowing or suction blowing in a final mould. Prior to the terminating press or suction blowing shaping of the intermediate body, a coloured layer is applied by, for instance, spraying metal oxide or metal powder onto the hot intermediate body, with the aid of a powder flash spraying process. The covering colour layer is oxidised immediately after being applied. The intermediate body is then dipped so as to embed the covering colour layer between two glass layers, in other words the colour layer is enclosed hermetically and no further oxidation takes place. The colour layer can become torn in the terminating shaping process, if the change in shape is large. This results in the formation of colour layer islands between the two glass layers. The embedment of the colour islands results in different degrees of cooling in the glass layers, which therewith obtain mutually different thicknesses as a result of individual stresses in the glass material. This results in light refraction effects.

Blasting or painting is used today to create patterns on glass products, for instance. A further glass layer is sometimes applied to a glass product after having blasted or painted said product. Another method of decorating glass is to produce a multi-layer glass in which the layers have different colours. The glass is then blasted to different depths, so that the colours will appear as a pattern where different colours are made prominent by the blasting process.

These methods, however, do not produce clear patterns. The object of the invention is to solve this problem. This is achieved in accordance with the invention by applying an enamel coloured decal to a glass blank that has cooled to room temperature. The enamel picture or image is fired onto the blank, whereafter the blank is allowed to cool. The glass blank is then reheated and a layer of glass is applied to said blank, for instance in the form of a gather. The blank is then brought to its final shape. The enamel colour decals can be made very rich in detail, therewith providing an enamel picture or image in fine and clear detail. The blank must not be stretched excessively, because the picture or image can then break up and become blurred. The major part of the description in this application document is concentrated on the manner of producing casing glass that includes an enamel picture or image. It will be understood, however, that many different types of glass objects that include enamel pictures or images can be produced in accordance with the invention, where an enamel colour decal is applied to a glass blank and a glass layer is applied to the blank in some way or another subsequent to having fixed the enamel picture or image by firing.

This type of .decal is used today for decorating porcelain, where the decal is applied subsequent to having glazed the porcelain. The decal is then affixed by firing. This type of decal has never been used earlier for decorating a glass product.

Another decal is today used for glass decoration, where the decal is seated outside the glass and is not enclosed within the glass. This decal withstands temperatures of about 530°C- 570°C and could not be used m the method according to the present invention. Glass decorated in this way is primarily pressed glass and the decal is fused with the glass m the last stage of manufacture.

EP,A1, describes a method for decorating glass products with enamel pictures. A glass blanket is blown, it is allowed to cool to room temperature and a colour print is applied. Then the glass blanket is heated under a short period to 560°C, whereafter it is covered with a layer of glass. By this method of decoration is the enamel not fired. A decor carrying layer, for instance paper which is coated with a sliding layer, is used. The enamel picture or image is placed thereon and on the top is a lacquer layer situated. Especially pictures with large subjects are used. An advantage with the method of decoration is mentioned to be that the enamel does not have to be fired and hereby is energy saved. The risk with waste of toxic colour pigments is also avoided since the decor picture is situated between two glass layers. A picture full of details may indeed be achieved, but the method is a different one than according to the invention and the firing of the enamel is avoided. According to the inventive method several pictures may be superimposed. This can not be achieved according to the method in EP 086 242.

In DE 204 899 is an example of firing enamel given. There is an enamel picture fired on a glass article, no further glass layer is gathered thereon.

There is obtained in accordance with the inventive method a detail-rich picture or image in a glass wall of a glass object. The invention provides a novel and unique possibility of decorating glass products in very fine detail. It is also possible to transfer a photographic picture onto the glass blank. Besides, several pictures may be superimposed if the film is burned away and the enamel is fired before the next enamel decal is applied. This is not possible according to the method in EP 086 242. According to the invention it is also possible to retouch pictures which have been damaged.

The invention will now be described in more detail with reference to the accompanying drawings which depict the manufacture of casing glass by way of example.

Figure 1 is a sectional view of a glass blank gathered on a glass blowpipe.

Figure 2 is a sectioned view showing the application of a decal to said glass blank.

Figure 3 is a sectioned view of the glass blank on the blowpipe, and shows the decal and gather.

The decal used is an enamel image placed between a film and a coated paper sheet. The paper is coated, e.g., with bone glue and the colour/colours then applied to the coated paper. This can be effected by screen printing or offset printing, for instance. The clearest images are obtained with offset printing. A layer which fastens to the colour/colours is then applied. This layer constitutes the film and may for example consist of collodium of lacquer.

The colour used is an enamel colour, which is a pigment of metal oxides mixed with glass paste or fusing agent. Cobalt oxide, chromium oxide and iron oxide are examples of such metal oxides, although the number of colours that can be used is very large. Enamel colours are used to colour porcelain, ceramics and glass, for instance. They are fused onto respective surfaces at different temperatures. Typical temperatures are 750-850°C. The colours boil when heated above certain temperatures, due to the properties of each colour .

The decal used is known to the art and is available commercially. It is intended for decoration of porcelain or ceramics. It is then fired at about 750-850°C. No further layer of any material is placed onto the decal.

When the decal is to be used and applied to the glass blank, the decal is first placed in water so as to dissolve the bone glue and release the paper from the colour layer, which is now fastened solely to the film. The colour picture or image is then applied to the glass blank, with the enamel proximal to the glass and the film distal therefrom.

The invention relates to a method of producing glass objects 5 with colour pictures or images 3 enclosed within a glass wall. A glass blank 1 is first blown on a glass blowpipe 2. The glass blank 1 is cooled and a decal 3, which is normally intended for porcelain decoration, then applied to the blank. The decal 3 is placed in water so as to release the colour picture or image from the paper, as before described. The decal 3 is stroked onto the glass blank 1 with the colour closest to the glass. In order to ensure that the film, of for example collodium, carrying the enamel colour will be in sealing abutment with the glass, the glass is first heated slightly, to a temperature of about 30-50°C, preferably about 40°C. The temperature to which the glass is heated shall be sufficient for the film to soften. The decal 3 may also be stretched slightly when applying a temperature slightly higher than room temperature. It is essential that no air bubbles form between the decal 3 and the glass blank 1 when applying the decal. Air bubbles present beneath the film are liable to burst during the heating and firing process. No dirt may be present between the decal and the glass surface.

Subsequent to applying the decal 3, the glass 1 is heated in a glass furnace so as to fuse to the glass surface. The film is burned away at the same time. The film is consumed at a lower temperature. The temperature applied will depend on the colour present on the decal 3.

The glass blank is then reheated and fastened to the blowpipe 2 and a new gather 4 is formed on the glass blank, by dipping the blank into molten glass. The glass casing 5 is then heated and brought to its final shape, e.g. by glass blowing. It must be seen that the glass object is not unduly stretched, because the decal will otherwise crack and the image become blurred.

The various steps undertaken in the manufacture of the casing glass 5, such as producing the first glass blank 1, cooling and applying the gather 4, are carried out conventionally. The novelty of the inventive method resides in the application of an enamel colour decal 3, intended for porcelain decoration, and the fusion of the decal to a glass surface prior to forming a glass gather. In addition, it has been necessary to adapt some temperatures because the glass is unable to withstand the temperature or because, m some cases, the enamel is unable to withstand the temperature. There follows a clearer description in which these amended temperatures are referred to.

After having produced the glass blank 1, it is cooled m a cooling furnace, wherewith the furnace has one start temperature and then the furnace temperature is slowly lowered down to room temperature. The residence time of the glass blank m the furnace and the furnace temperature will depend on the sort of glass concerned and on the thickness of the glass products. An example of the starting temperature m the cooling furnace is about 460°C m the case of crystal glass and about 490°C m the case of lead-free glass. The residence time may vary from a few hours to several days. This stage of manufacture is carried out conventionally.

After removing the glass from the furnace, the glass can be further worked, for instance ground and polished.

Subsequent to this first cooling process, the glass is heated slightly, e.g. to about 30-50°C, preferably about 40°C, so as to enable the decal to be applied. The decal has lain m water, so that the enamel picture or image and the film will release from the coated paper. Several decals can be applied simultaneously, provided that they are not placed on one another such that a film layer of for example collodium or lacquer becomes located beneath a colour layer. This inventive step is entirely novel m obtaining a detail-rich enamel picture or image encased m the glass wall. Heating of the glass blank facilitates application of the film carrying the enamel image or picture.

The glass blank 1 carrying the enamel picture 3 is now placed m a furnace in which the enamel colour shall be fused to the glass surface and the film burned away. The furnace is cold initially and its temperature is raised successively to about 600°C. The temperature is maintained at about 600°C for about ten minutes and then allowed to fall. The time during which the furnace is maintained at the highest temperature will depend on the thickness of the glass and will be sufficiently short to ensure that the glass will not collapse. The length of time during which the glass can withstand the temperature without collapsing will depend on its thickness. This step is repeated when several images or pictures shall be superimposed. The film of for example lacquer or collodium from a first enamel decal will make the next imposed colour picture to be destroyed if the film is not burned away and the enamel fired at first. To superimpose pictures it is not possible with the technique used m EP,A1,086 242. In the case of this latter use, the decals used at present m the manufacture of porcelain and ceramic goods are fired at a temperature of about 750-850°C. According to the invention, slightly lower temperatures are used when the glass is unable to withstand temperatures as high as 750-850°C, for instance temperatures in the range of about 550-620°C, preferably a temperature of about 600°C. The glass will begin to collapse at temperatures of 750-850°C. It has now been found that the enamel images or pictures can be fused to a glass surface at a temperature of about 550-620°C, preferably a temperature of about 600°C, which enables glass objects to be produced with said enamel pictures encased within a glass wall.

The blanks 1 are then placed m a blank furnace whose temperature is raised from room temperature to a temperature of about 470°C. The glass blanks 1 are removed from the furnace with the aid of the pipe 2 and moved into the heating furnace. This step is a heating step. In conventional glass manufacture, the heating furnace has a temperature of about 1600°C. The temperature of the heating furnace is now lower, for instance about 1100-1400°C, preferably about 1200°C, so as not to destroy the enamel colour. Care must be taken in this step, because of the delicateness of the enamel picture. It must be ensured that the enamel picture or image is not heated for too long a period at this temperature. Usually it is heated to about 470-600°C. This temperature has been adapted to the method according to the invention in order to not destroy the enamel picture. The glass blank is then passed on the pipe into a glass bath, from which a gather is made on the blank. The blank is then returned into the heating furnace at the same temperature. The glass blank is finally formed in a conventional manner, e.g. by blowing. The glass 5 should not be over-extended during this final shaping process, when it is not desired that the enamel image 3 will crack or become blurred. Several gathers can be formed one on the other. The blank is allowed to cool slightly between different gathers, so as to enable the glass to stabilise. There is otherwise a danger that the glass will melt out.

The decals used may be single coloured or multicoloured. It is also possible to apply several decals. When several decals shall be applied without intermediate firing, the film layer of collodium or lacquer of one decal must not become located beneath the colour of another decal. The layer of collodium or lacquer must be burned away before several decals can be superimposed. Highly detailed images and pictures can be produced in glass objects, which was not earlier possible. Another advantage is that images and pictures can be retouched when an error or fault is discovered on a decal that has already been applied. A fault or error can be corrected, by applying one enamel picture on top of another.

There has been described above a method of manufacturing a glass object in the form of a casing glass that encases an enamel image or picture. This is not the only type of glass object that can be produced in this way. Other glass objects can be manufactured in accordance with the invention, by first producing a glass blank and then fusing an enamel coloured decal onto the blank surface and applying a glass layer onto the decal. In the manufacturing method, the step of applying a gather to the glass blank has been replaced with another method of applying a further glass layer. For example, an enamel picture or image can be applied to the boss of a basin and fused onto the surface. The boss is then the glass blank, according to the method. The boss to which the enamel image or picture has been fused is then placed in a mould designed so that the boss is lowered in the mould. Molten glass is then poured into the mould over the boss and the glass centrifuged in the mould so as to form a basin above the boss (rotation cast) . A detailed enamel picture or image is herewith obtained in the bottom of a glass basin.

The invention also relates to a glass object which includes an enamel picture or image and which has been produced in accordance with the inventive method.

The invention provides a method of embodying in the wall of a glass object enamel images or pictures that are very rich in detail, which has not earlier been possible with the aid of known techniques. Besides, several decal pictures may be superimposed by the method according to the invention and it is also possible to retouch pictures. By using enamels pictures intended for porcelain manufacturing and by virtue of changing the conditions that were normally employed a novel method of glass manufacture has been achieved.

A picture full of details in a glass wall is obtained.

Claims

1. A method of producing glass objects with colour pictures or images encased within a glass wall, characterised by producing a glass blank, cooling said glass blank in a cooling furnace, slightly heating said glass blank, transferring a colour picture or image in the form of an enamel colour decal on film onto said glass blank, placing said glass blank in a furnace and heating said blank such as to first burn away the film and thereafter fuse the enamel to said blank surface, allowing the glass blank to cool, reheating the glass blank and applying a glass layer thereto, and thereafter forming the glass object.

A method according to Claim 1, characterised by heating the glass blank to a temperature sufficient for the film to soften, e.g. a temperature of about 30-50┬░C, subsequent to cooling said blank in the cooling furnace.

A method according to Claim 1, characterised by fusing the enamel image or picture at a temperature of about 550-620┬░C, preferably about 600┬░C, over a time period which is sufficiently short to ensure that the glass will not collapse.

A method according to Claim 1, characterised by reheating the glass blank in a furnace with a temperature of about 1100-1400┬░C, preferably about 1200┬░C, prior to applying said glass layer.

A method according to claim 4, characterised by reheating the glass blank to a temperature of about 470┬░C-600┬░C.

6. A method according to any one of the preceding Claims, characterised in that the glass layer applied to the glass blank has the form of a gather.

7. Cased glass with a colour picture or image embodied in the glass wall, characterised in that said cased glass has been produced in accordance with the method of Claims 1-6.