a) Earth is the name of the planet which we inhabit.
b) Earth is the ground, all the soft inorganic matter that makes up part of the world’s surface, soil of all kinds, gravel, clay and others.
Earthenware: is a ceramic material, clay that has been fired to become bisque and used for decorative and practical work. The formulation of clay bodies differs depending on the source and in the past, ceramic businesses grew up round places where good quality clay could be found. In those days, one factory did everything from digging up the clay to selling the finished pieces. The composition of clay is 25% ball clay, 28% kaolin, 32% quartz, and 15% feldspar. The most common clay is red clay that can be fired between 600º C and 1100º C. At 600º C, it becomes solid, unpliable, but it should be fired to a higher temperature to stop it shrinking and make it stronger. The firing changes it into a solid, breakable but still porous material which is called bisque. White and buff colored earthenware clays are available. Earthenware is not as strong and more porous than stoneware, but it is cheaper and easier to work with. It’s used industrially for many products such as bricks, flower jars, etc ., and when glazed, it is no longer porous and is used for domestic ware.
ca: PISA ESMALTADA
es: LOZA ESMALTADA
Earthenware glazes: they are glazes that vitrify below 1150º C and are usually smooth and shiny. They are mixed with products to make an opaque white glaze. This is known as a glaze-base and can be used to decorate in many different ways, forming very bright colors. Luster, Majolica (in-glazing), on-glazing and slips are some of the methods that it is used with.
es: CABALLETEClick on the title to see more images
Easel is a stand for displaying and working and can support a canvas, blackboard, tiles, plates, etc. There are several different types, including portable ones that can be folded and in the illustrations below there are three; the first one on the left slants, it is light and the legs can be closed; the center one is good because the main part can be straight or moved backward; and the last photo shows the easel I have in my studio that is straight and has wheels. They all have two bars; each has a fence on the outer edge to stop what they hold from slipping off and they can be moved up and down to support work of different sizes. I prefer the straight ones because if you work for many hours it is better for your back. For painting or displaying tiles and plates, stands are used.
Read more about: Plate – Stand / Tile – Stands
ca: FAIANÇA EGÍPCIA
es: FAENZA EGIPCIA
Egyptian Faience Due to limitations of the Egyptian paste, especially in manufacturing large pieces, they used paste Faenza, with it they built the parts, then glazed them with ancient Egyptian paste.
(Later, starting with the formulation of the ancient Egyptian paste it obtained a “firing” that maintaining its characteristic colors, using it as a glaze and pigment for ceramics, glass, painting …).
I have been given permission to use this section written by Amy Waller from her web. At the end of her web there is a video and excellent list of articles, books and museums that cover this subject.
Link Egyptian Faience.
ca: PASTA EGÍPCIA
es: PASTA EGIPCIAClick on the title to see more images
Origin. Egyptian paste was developed in ancient Egypt between 2686-2181 BC., a period during which jewelers used casting and for this reason ceramic glazing is closely linked to the metallurgy of copper and bronze. (There is no link or relationship with Faience).
Definition. It is a self-glazeable mass with a sandy texture, its composition is related to glass and it is a very siliceous paste mixed with alkaline salts and has little or no plastic materials or oxides.
This paste has the property of self – glazing (auto-enameling) and is characterized by its final color, a bright blue. Sometimes it is decorated with manganese oxide (black).
Auto – enameling. This action is carried out by all the alkali metal salts and metal oxides during the drying process. These elements are stretched and drawn to the surface as it dries and form a glaze by creating efflorescence’s. These vitrify when fired due to the presence of silica (glass-forming) across the surface, giving brightness and color, all in a single firing. This is called “efflorescence glazing.”
*Utility. + In ancient Egypt it was mainly used for making very small pieces of jewelry, amulets, small funerary statues, due to the difficulty of working with it.
Composition. Today the raw materials to form the paste are made, but in the original era, the Egyptians were using base components that could be found locally (river, land, desert sand ….).
To start with it is a strongly alkaline paste with little plasticity, something very special, and its composition can vary greatly depending on its final use.
In the composition of the base: silica, feldspar, chalk, kaolin, sodium carbonate, sodium bicarbonate are usually involved, as well as fine sand and ash from firing, which gives the famous Egyptian blue shades. Other oxides can be added to develop different shades.
Base Egyptian paste glossy 850º C
Silica …………………. 75 gr.
Crete ………………… 3
K feldspar …………. 2
Ball Clay …………… 5
Na carbonate ……. 4
Bentonite …………. 3
Blue – Cobalt Oxide 0.5% to 2%
Turquoise – Copper Oxide 1% to 3%
Purple – Manganese oxide 1% to 4%
Preparation. It is essential to have all materials and equipment ready before you start the process, since it is a very demanding paste and should be worked very quickly.
1) The base weighed
2) A large mortar
3) A rigid or semi-rigid plastic spatula
4) A plastic sheet
5) Distilled water or rainwater
6) A bottle or tube to measure the water
7) A sieve
8) Very important: dust mask and rubber gloves.
How to prepare it
a) Weigh the base, mix it thoroughly until you have a homogeneous dry mixture, then pass it through the sieve.
b) Put the distilled or rain water in a measuring bottle, you don´t need too much water and it should be added very gradually.
c) Put the base in a mortar, add the measured water and mix it with the spatula. Be careful not to add too much water, because it can easily become liquid.
Having prepared the paste in a lump, it can be worked and given its final shape, following the design chosen and the technique to be used.
d) Caution: the paste should be worked quickly and continuously without handling it excessively as it tends to get wet and softens easily. You should start and finish the piece without interruption, if left too long the final result will not be satisfactory.
e) If you want to work the paste with a press mold, it must be made of fired clay as otherwise the cast will be contaminated with salts which will make it unusable.
f) Another way to treat it is as a slip.
g) When handling this paste extra protective precautions must be taken: dust mask and rubber gloves to avoid contact of the paste with the skin.
Drying. This process lasts a minimum of two to three weeks.
It is important that during this period the whole piece is oxygenated, because the parts which are not will not be glazed.
During this process the piece should not be touched so as not to spoil the glaze and colors. The atmosphere of the place where you work determines the drying: cold, heat, humidity, etc., all directly influence the final result.
Decoration. Any type of decoration to be added must be finished before the drying process, as it is impossible to work on the piece once the efflorescence has appeared.
Firing. The ideal temperature is between 850º C and 1050° C depending on the composition of the base.The increase in temperature during firing should be very gradual over a minimum of 8 hours and cooling should be slow also.
When firing Egyptian paste, the interior of the kiln should be protected as small drops of enamel tend to detach themselves from the piece. It is very important to fire the piece as it has been dried, so as not to have to touch it when unfired.
Link to Author – Maria Teresa Capeta
ca: FORN ELÈCTRIC
es: HORNO ELÉCTRICO
Electric kilns developed during the last century for use in small businesses such as in schools, studios and craft centers. Kiln temperatures were controlled by pyrometer or cone, but kilns are now made so that the whole process of firing is done automatically. Kilns are an essential tool in the manufacture of all ceramics for the firing of clay and glazes at different temperatures and there are many different types.
a) An element inside a kiln is coil-shaped and produces the heat.
b) Pure chemical elements: below are two lists, the first contains the names of the elements in alphabetical order with their chemical symbols and the second is in reverse, the symbols are in alphabetical order.
c) Element; doing what one enjoys or one is naturally good at.
|Name||Symbol||Atomic weight||Melting point ºF||Melting point ºC|
Elorescence in clay: is bits of white scum in red clay which cannot be seen but when the clay is fired and becomes bisque; they can form white spots in the surface which are very difficult to remove. If removed they will leave an indent and if glazed will expel the glaze at that point.
Enamel colors: they have a large and spectacular range and are applied to ware which already has a fired glaze. Their firing temperature is between 700º C and 850º C. The process can be repeated several times by adding colors that vitrify at the same or lower heat and using methods such as painting, screen-printing and spraying. These colors can be bought already prepared or you can prepare them yourself either with turpentine, oil, or colorless varnish, all natural products that burn away. Enamel decorating is also known as on-glazing, which means firing three times, bisque, glaze and decoration. With this method and at this temperature, transfers can be used.
Read more about: On-Glaze / Transfer
Engraving: is to cut and indent into clay to form a design or texture. The clay can be at any stage of drying and the harder the clay, the sharper the lines. This type of decoration was traditionally covered and fired with a colored transparent glaze and as the glaze is thicker at the indented parts, it deepens the color. It is also known as incising. Read more about: Incising
Equipment refers to tools and all forms of accessories needed for a job. Each piece or pieces are described under their name and in special sections under the generic name of a subject, like kiln furniture or clay tools.
Read more about: Clay (7) accessories / Clay (8) Tools / Brushes – Decotating / Kiln furniture
Expansion: most materials expand with heating and contract with cooling. Clay shrinks when being fired and goes on shrinking until it reaches its set heat. It does not alter when cooling but the glaze shrinks and if the balance between the two is not correct, this difference between the biscuit and the glaze is what causes crazing.
Extruder: there are two types of extruders, which work with electricity or by hand and each has many variations.
Hand controlled extruder passes clay, clean and well kneaded, through a tube to form coils, which are used to make handles, applied decorating and coiling.
Electric controlled extruder is a machine for compressing and recuperating clay so that it can be used again, this also improves its strength and workability. It breaks down the clay and shapes it into a solid tube, known as a coil. There are many different sizes and types, for big industrial business and for small studios and schools.
Read more about: Extruda (a) Manual / Extruder (b) Electric / Extruder (c) How to keep it
Extruder is a tool that passes clay through a tube to form coils, which are used for handles on jugs, cups, teapots and for applied decorating. There are different types that can be hand-held or attached to a wall or table. They use dies which are metal disks with spaces cut out to extrude different shaped coils. The clay that is used must be clean and well kneaded.
The following explains each illustration.
1) Shows how the tube pushes the clay down through the die.
2) Gives the names and show each section of an extruder.
3) Syringe extruder. The die is attached to the bottom, the tube is filled up with clay, then the handle is pushed down and this expels the coil through the die.
4) Table extruder. It is attached firmly to a table or shelf, which it overlaps leaving enough space for the coil to be expelled. The handle is attached to a long screw which has a disk at the end. The tube is filled up with clay, the handle is turned, this pushes the disk down through the tube onto the clay which goes down and out through the die to form a coil.
5) Clay Gun Extruder: the pressure of closing the trigger pushes and turns the screw which moves the plunger down through the tube, making the clay come out through the die.
The clay must not be left to harden in the tube, start the process of cleaning as soon as you have finished what you were doing. Periodically oil the screw with drops of mineral oil.
Note: They are known under different names, in the dictionary these names are placed correctly with a short explanation and then linked to this article. Dod Box and Wad Mill are different names used for the same product. Photos lent by. Ceramic Material
Extruder – electric also known as a Plug Mill. It is a machine for compressing and recuperating clay so that it can be used again and it improves its strength and workability. There are many types of extruders for big industrial businesses and for small studios. They are made for mixing clay into a usable, pliable state and expelling it in large coils.
An extruder should only be used for one type of clay as cleaning them well is nearly impossible and clays should not be mixed. When clay is in the state to use but has too much water, never separate it from the water as it has many substances that it needs. Let it dry until it can be passed through the extruder.
The large industrial ones are used in the final stages of making clay that has been taken out of the earth, dried, sieved many times using meshes that are gradually getting finer and finer, then mixed with water, passed again through a sieve and left to dry to a pliable state, then passed through the extruder.
These photos show one of the smallest that is simple and good, with an arm that forces the clay down which is pulled across from one side to the other. Many are made with arms that move length wise.
The neck is filled up with clay and with the machine working the handle is pulled down, this forces the clay down and through the mixer, then the lid is lifted and more clay is added. This is repeated and the pressure pushes the clay down the tube forming a large solid coil until it comes out on to the long plank at the front and can be sliced into the lengths needed with a wire cutter.
How to keep the extruder in a good working condition when not being used.
When you finish working there is always clay left in the machine so it must be packed and kept so it is always pliable, never let it dry and become hard.
a) This shows the extruder prepared for storage. The mouth where the coil comes out has a plastic lid, put a piece of damp material between it and the clay and cover the outside with plastic and tie tightly in the same way as the neck.
b) Put a plastic bag inside the neck, push it down as far as possible, flatten it round the inside walls and bend the top over the edge of the neck on to the outside, the less air the better. Then put a damp rag in another plastic bag, close it and leave it inside. Cut a plastic bag into a long piece and tie it round the plastic on the outside wall of the neck and shut it. This will keep the clay from drying, remember to occasionally dampen the rag.
Extrusion is forcing clay through different objects, tubes, wire nets, kitchen utensils, etc., or through a die plate. With these, the clay comes out as a tube in the shape of the die. The dies have a special design and can be hollow or solid. The solid ones are used for applied decoration and to make handles.