EP0786538A1 - Metallic kitchen utensil coated with a transparent enamel - Google Patents

Abstract

An aluminium cooking utensil is at least partly coated with enamel containing no pigment or only a small amount of colouring pigment, so that the underlying metal surface is visible through the enamel.

Description

The present invention relates to a metal cooking utensil covered at least partially by a layer of enamel.

Enamel coatings on metal cooking utensils have different purposes, such as anti-corrosion, color fastness to light, abrasion resistance, chemical resistance, thermal resistance, but also and above all particularly on metals such as aluminum, a decorative purpose.

It is indeed possible to obtain with enamel all the colors of the rainbow.

The science of the enameler or enamel fryer slip formulator consists in obtaining the most stable color formula during vitrification, the most covering and the most reproducible from one series to another with the best quality ratio. -price.

Only a few so-called majolica enamels, colored with fusion, generally provide depth and moiré effects on a white undercoat.

On the other hand, it is at no time possible to perceive, as a decoration, the surface structure of the metal of the culinary utensil.

The present invention proposes to the enameller, in particular on aluminum, to have a coating with a transparent color making it possible to appreciate the surface texture of the metal and to give an innovative concept of "material" and no longer of coating on the material (such as varnish on wood preserving the wood side compared to painted or lacquered wood).

Thus, according to the invention, the aluminum cooking utensil covered at least partially by an enamel layer is characterized in that the enamel layer is devoid of or lightly charged with coloring pigments so as to be sufficiently transparent in order to allow the surface texture of the underlying metal to be perceived.

Contrary to the practice implemented until now, the transparent enamel layer reveals the surface texture of the metal, that is to say the traces limiting the grain boundaries resulting from a chemical attack, the roughness obtained after a surface treatment, the surface condition obtained after EDM or other chemical or physical treatment.

Tests have shown that what we have tried to mask up to now with colored, i.e. non-transparent, enamel layers gives the utensil in combination with a transparent enamel layer, a particularly attractive aesthetic effect.

• d'un prix de formule inférieur à celui d'une formule couvrante,
• d'un prix de revient process inférieur à celui d'une formule couvrante, puisque les différences de teintes dues à des différences d'épaisseurs et induisant à des rebuts sont, de ce fait, éliminées.

This new concept is also advantageously accompanied by a certain economic gain, namely:

• a formula price lower than that of a covering formula,
• a process cost price lower than that of a covering formula, since the color differences due to differences in thickness and leading to scrap are therefore eliminated.

This new concept also makes it possible to use rapid and economical turbine or flow coating application methods.

In a first version of the invention, the enamel layer is obtained from an enamel frit devoid of coloring pigment.

In this case, the transparent shade obtained will change according to the nature of the enamel.

Thus, vanadic enamels will color the surface yellow: ex. : GL 4317 from FERRO or AT 6118 from BAYER.

Others, of the pure alkaline fondant type, will respect the metallic shade of the support (e.g. AL 411 from WENDEL).

In a second version of the invention the enamel layer is obtained from an enamel frit slip containing a very small proportion of coloring pigments in order to obtain a colored but transparent enamel layer.

This second solution therefore consists, for coloring the enamel, of using a very small percentage of mineral pigments in order to obtain transparency, but it has the disadvantage of being very sensitive to the different thicknesses.

In a third version of the invention, the enamel layer is obtained from an enamel frit slip containing an enamel frit colored by means of a pigment, diluted in an enamel frit devoid of pigment.

This third solution therefore consists in using fusion colors cut or not with transparent enamels.

Thus the VP PK 61/2339 enamel fused with iron oxides gives earth or brown coloring.

Thus the blue FERRO GL 288 enamel gives more or less diluted blue colors.

In this third version, the enamel layer is obtained from an enamel frit slip containing less than 3% by weight of coloring pigment.

In a fourth version of the invention, a colored pigment with very little coverage is used, such as transparent iron oxide of the Cappelle type.

In another version of the invention, the culinary utensil comprises several layers of transparent enamel more or less charged with pigments of different colors.

This combination of several transparent layers of different colors can provide a reinforced decorative effect while revealing the surface structure of the underlying metal.

Several examples are given below of compositions of enamel frit slurries which can be used in the context of the present invention.

Cappelle type transparent iron oxides are therefore perfectly suited for this use. Example 1 GL 4317 frit 100 Boric acid 4 Soda metasilicate 1 Caustic potash 1 Water 56 Example 2 Fritte GL 4317 100 Boric acid 4 Soda metasilicate 1 Caustic potash 1 Mineral pigments 0, 1 to 3 Water 56 Example 3 Fritte AL 288 5 Fritte GL 4317 95 Boric acid 4 Soda metasilicate 1 Caustic potash 1 Water 56 Example 4 Fritte GL 4317 100 Boric acid 4 Soda metasilicate 1 Caustic potash 1 Iron oxide Cappelle 2 Water 56

The above enamel frit slurries are sprayed directly onto the metal of the cooking utensil previously chemically or physically treated.

The layer thus pulverized is then baked in the oven at a temperature between 500 and 600 ° C.

Of course, the invention is not limited to the examples which have just been described and numerous examples can be given to them without departing from the scope of the invention.

Claims (7)

Aluminum cooking utensil covered at least partially with an enamel layer, characterized in that the enamel layer is devoid of or only slightly laden with coloring pigments, so as to be sufficiently transparent in order to allow the surface texture of the metal to be perceived underlying. Culinary utensil according to claim 1, characterized in that the enamel layer is obtained from an enamel frit devoid of coloring pigment. Culinary utensil according to claim 1, characterized in that the enamel layer is obtained from an enamel frit slip containing a very small proportion of coloring pigments in order to obtain a colored enamel layer but transparent. Culinary utensil according to claim 1, characterized in that the enamel layer is obtained from an enamel frit slip containing an enamel frit colored with the melting of a pigment, diluted in a frit of enamel devoid of pigment. Culinary utensil according to claim 1, characterized in that the enamel layer is obtained from an enamel frit slip containing less than 3% by weight of coloring pigment. Culinary utensil according to claim 5, characterized in that the pigment is transparent iron oxide of the Cappelle type. Culinary utensil according to one of claims 1 to 6, characterized in that it comprises several layers of transparent enamel more or less charged with pigments of different colors.