The present invention relates to a process for the production of brick products with a finished surface, e.g. bricks, with a surface coating consisting of glaze and/or a vitrified ceramic mass, on at least one of the side faces of the brick product which in the baking oven, when non-baked brick products are stapled one upon the other, forms a contact surface with a layer above or below of brick products £n the baking oven and/or on at least one free side surfaqe of the stapled brick products.

It is known technology to provide ceramical objects/brick products with glaze. A glazed brick product, e.g. a brick, is produced by first baking the dried brick blank, whereupon the brick product is provided with glaze and is baked once more. This is a time consuming and resource consuming process which, e.g. in production of bricks, will make the product much more expensive.

In production of brick products, e.g. bricks are baked in a baking oven without any kind of fixtures, e.g. shelves, upon being dried. The dried brick blanks are stapled directly one upon the other to a height that may be tolerated by the underlying brick blanks without the latter being compressed by the load, and in the volume for which the oven was intended. If it is desired to provide glaze on the brick in the first baking process, the glaze will act like a glue curing between the brick blanks stapled one upon the other during baking. After baking it would not be possible to separate such bricks with a glaze without heavy damage to the glaze.

It is an object of the present invention to provide a process, by which a finished surface of brick products may be

achieved in the first baking of brick products which are stapled one upon the other during baking, by only being baked once, with use of a surface coating consisting of a glaze and/or a vitrified ceramic mass.

According to the present invention this is achieved by the aid of the features appearing from the characterizing part of the following independent process claim as well as the following dependent claims.

The invention will be disclosed in more detail below with reference to the drawings, diagrammatically showing some embodiments of bricks with a surface coating.

Figure 1 shows brick blanks which are stapled one upon the other with intermediate spaces in a baking oven, not shown.

Figure 2 shows a brick blank with a surface coating on a vertical side face.

Figure 3 shows a brick with a surface coating on a horizontal side face.

Figure 4a shows a brick with a top face provided with recesses that are filled with a surface coating.

Figure 4b is a sectional view of a fragment of the same, in a larger scale, and

Figure 5 shows a fragment of a brick in a larger scale with projections and recesses in its top face, which has a surface coating showing damages in the projecting portions of the surface coating which were in contact with overlying bricks during baking.

In Figure 1 brick products in the form of brick blanks 1 are shown to be stapled one upon the other in a baking oven, which is not shown. Said brick blanks are in contact with one another at their top faces 2 against the lower faces 3 of adjacent brick blanks.

Before said stapling of brick blanks l they may be provided with surface coating material 4a in a liquid plastic or dry form on at least one of their vertical faces 4a, as shown in Figure 2, whereupon the brick blanks are dried and stapled as shown in Figure 1, before being baked once to form a finished brick with at least one finished vertical face 4. The contacting upper and lower faces 2 and 3 of adjacent brick blanks 2 are not provided with surface coating material and will, thus, not adhere to each other after baking. In this surface finishing process of the brick blanks the upper surface coating used may be a glaze and/or a ceramic mass for vitrification. ^* *

In Figure 3 a brick 2 is shown with a finished upper face 2 having a surface coating 2a. To prevent the surface ooating 2a from adhering to lower face 3 of an adjacent brick 2 after being baked once, the surface coating used may be a ceamic mass which is transformed from a liquid into a vitrificated state during baking.

Obviously, the surface coating 2a in Figure 3 may in stead be provided on the lower face 3 of brick 2 with the same result.

In Figure 4 a brick 1 is shown with recesses 2b in its upper face 2, which recesses are filled with glaze 2c, as more clearly shown in Figure 4b, which shows a fragment of brick 1 in a sectional view. When brick blanks l are stapled one upon the other for baking as shown in Figure 1, the edges of recesses 2b will contact the lower face 3 of an overlying brick blank 1, and said brick blanks will not be made to adhere when baked. The bricks can, thus, be separated and a

lateral face 2 is provided which is partly covered by a surface coating, resulting in a finished surface with a special appearance which is achieved by the coated and non- coated portions of lateral face 2.

Brick blank 1 with said filled recesses 2b on its top face 2 may, obviously, be turned around during stapling, as shown in Figure 1, so that recesses face downwards and said face is then the lower face 3 of the brick blank.

Figure 5 shows a fragment of brick or brick blank l with its top face 2 provided with projections 2d and recesses 2e. By providing a surface coating on the entire face 2 and then stapling brick blanks 2e as shown in Figure 1, the surface coating 2c which was applied to the entire surface 2 will after baking in a baking oven show scars on the projecting portions 2d which were in contact with the underside 3 of an upper brick blank 1, if a glaze was used for a surface coating which during baking goes through a sticky phase causing adherence between adjacent faces 2,3.

By using a ceramic mass for a surface coating, which reaches a vitrified state during baking, adjacent faces 2 and 3 will not adhere to each other and no scars 2f will appear in the surface coating when the bricks are separated.

For a ceramic mass for providing a vitrified surface coating a glass forming raw material is used together with silicate substances preventing the resulting mixture from melting to a sticky mass during one baking process.

In a process according to the present invention bricks may be produced one or a plurality of side faces of which are completely covered by the desired surface coating.

Also, bricks 1 may be produced, the desired side face of which is partly covered with surface coating 2c in recesses

2b, resulting in a side face with a pattern of coated and non-coated portions.

Furthermore, bricks 1 with recesses 2e and projections 2d in a regular or irregular pattern may be produced, and with surface coating 2c covering the entire side face, but showing scars 2f on the projections 2d where the side facl ^* was in contact with an adjacent brick during baking in a baking oven.

By this process it is, thus, possible to provide brickέ with a side face having a attfinished surface and with glazed portions, and/or a vitrified ceramic mass on portions of or on the entire surface. By the aid of the process it is, thus, possible to provide bricks 1 with a very varied appearance of the finished surface.

In order to achieve coloured surfaces, dye pigments may be added to the surface coatings, as known per se.