ENGOBE

Ceramic engobe is a fundamental and very versatile element. It is a very useful aesthetic resource to be used in the pieces, being used many times as a painting.

Learn about its applications to achieve the desired finish in pottery works.

In this guide we explain what engobe is, what it is composed of, how it is made, what formulas there are for different effects, the difference with other types of materials and techniques used in ceramics and its interesting and useful properties, among many other things.

ENGOBE IN CERAMICS

The ceramic engobe is the solution of earthy materials in water, basically speaking, it would be a mixture of clay and water. It is also known in pottery as engalba. In this sense it could be considered similar to barbotina, however, they are often not the same in terms of composition, so they must be differentiated from each other; furthermore, a definition of engobe simply as mud and water does not explain its meaning well.

The difference between engobe and barbotine:

Deflocculant materials are used in the engobes. This “word” that you will find many times in the definitions of engobe on the Internet and that many pages do not explain, refers to those materials that prevent the agglomeration of the particles that are in suspension in a liquid.

This is especially important when the particles are very fine. In this way we achieve a mixture with less viscosity and that, in addition, admits a greater quantity of them.

Another difference with slip is that the engobe can be produced with less clay, and it usually contains fluxing elements. Fluxes are chemical products that lower the melting point of other materials, i.e. they melt faster. Fluxes also aid in the process of making the clay liquid.

Another element contained in most compositions is silica, which will “vitrify” the mixture. The different vitreous elements contained in the engobe that contribute to modify its properties, such as the color of each preparation, are often referred to as ceramic “frits”.

Difference between engobe and glaze:

It is due to the proportion of material that gives the engobe the ability to vitrifyThe latter does not become as large as in the case of enamels, since the latter produce a real vitreous layer when fired, which gives it a vitreous finish. much brighter than with engobing.

Summarizing all these technical characteristics, it could be said that the engobe has properties that place it between slip and glaze, being closer to one extreme or the other depending on its composition. The interesting thing about being “in between” the two makes it suitable to be applied as a primer, since it would serve to unite both materials: the clay and a glaze that we are going to apply on top.

What is an engobe:

The definition of engobe is the mixture of clay and water that also contains deflocculants and fluxes, which place it between slip and glaze in terms of its properties, which may vary (including color), depending on its composition.

ORIGIN AND APPLICATIONS

The engobe, understood simply as the mixture of clay and water, is as old as ceramics itself. In ancient Greece it was already used by applying it before firing the piece, in the Roman Empire it is still used to give different shades of color to the works, then in different locations and times it has been used according to each pottery tradition to create different finishes and colors, using different layers and using decorative techniques such as incision or sgraffito.

With industrialization and the subsequent use of more and more specific mixtures, we have reached our days where there is a great variety of commercial brands with an infinite offer according to their colors and their capacity to glaze to a greater or lesser extent.

As for the ways of applying it (or “engalba”, as we mentioned before in pottery), they can be infinite according to the creativity of the artist, below we detail some decorative methods.

The engobe can be applied on the piece in various states of humidity: raw unfired or in leather state, which for some more precise decorations or drawings that we do not want to be blurred, can be the best.

After applying the engobe, it is left to dry a little and burnished.

If we are going to apply a transparent glaze over the engobe later, another possibility is to apply the engobe, fire the piece, apply the glaze and fire it again.

DECORATION WITH ENGOBES

We are going to mention the main techniques used, maybe some of them will give you ideas to try.

We can submerge the piece by covering it completely, which would be immersion, or we can cover only a part of it by introducing it into the engobe and then turn it upside down so that the liquid drains down and creates a nice dripping effect.

Coat completely with a broad brush or apply with a sponge, sometimes without pressing completely and covering only parts of the surface.

Using it for fine lines or drawings, using for example a fine brush.

Spraying it on the surface (we can cover certain areas so that it does not reach them and thus create decorative areas of contrast, this technique of covering parts of the surface is called masking).

Applying at the same time two tones of engobe that will generate a marbled effect by the mixture of both.

It is also possible to apply some layers on top of others by combining different techniques of the previous ones.

On a piece with a layer of engobe, already in a leather-hard state, areas of the surface can be scraped to expose them, creating a decorative pattern, using sgraffito. Afterwards, another layer can be applied on top of it.

Ceramic decoration with engobes is not only limited to the different tones, but can also be used for use the volume of some surfaces compared to others, applying more layers, using a vitrifiable engobe next to another one that is hardly vitrifiable, and adding elements that give it a certain texture to the part such as dry sand, iron filings, etc.

We include here a video about laying a foundation for layered surfaces with ceramic engobes

HOW TO MAKE ENGOBE: FORMULAS

A composition to make our own engobe can be, in general terms, the following:

• clay (which may have among its components a greater or lesser quantity of kaolinite. The amount of kaolin, which will give it a more or less white tone, and according to this amount we can speak of kaolin when it is a clay with a very high content of kaolinite, or of ball clay when the content is lower.
• a flux,which is a common element with enamel and
• silica (silicon oxide) or wollastonite (which also reduces shrinkage due to drying or cooking).

On it we will apply the colorants (natural oxides or other pigments) that we need to achieve the color that we are going to use.

A very important feature is to mortar all dry elements.

The ideal before preparing an engobe mixture is to have a clear idea of what we want to achieve (color, viscosity, vitrification, etc.) and then get down to work with the right proportions of materials. What if we don’t and want to experiment? Sometimes the magic of ceramics can give us beautiful “accidents”. It is up to each individual.

If you want to have a place to consult about all the materials for ceramics, their compositions, classifications, “recipes”, etc. there is a very useful page here.

Examples:

Here are some engobe formulas to give you an idea. The exact resulting color it will give is difficult to predict, there are always variations, for example, the different ball clays that can be purchased vary in shade.

In addition, it is best to consult the pigment tables of the specific manufacturer from whom you are going to buy the materials.

PAINTING WITH ENGOBES

Using engobe as paint is very common and, as you have been able to deduce, the variety of colors is infinite. In the stores of ceramic materials they have many different preparations of already defined colors, with the convenience of only having to open the product and use it.

However, we may want to experiment with creating our own formulas and mixing variations, which can be fun, part of the creative process and also more economical if we want to prepare a large quantity of product.

For the different colors you can use oxides, in addition to the pigments you have seen in the formulas; for example, for green, chromium oxide, for blue engobe, cobalt oxide, for ocher, copper oxide, for red, iron oxide. In your material store they can advise you on engobes already made and also on the components to make them yourself.

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