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Research into steps in making different kinds of sculptures

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Research into steps in making different kinds of sculptures

  1. 1. Research into steps in making different kinds of sculptures. <br />Steps in making Clay to Bronze for sculptures. <br />Step #1: complete the original positive: The original sculpture is completed. This sculpture may be in clay, wood, stone or metal. This is the first positive.<br />Step #2: make a negative mould: A mould is made of the original by coating it with rubber supported with a plaster "mother mould". This is done by encasing the original sculpture in rubber applied in layers. Most sculptures will require several parts to the mould. For example, a torso might be one part of the mould, and a leg another, and a head another. The original is now removed from the mould making the mould empty. The empty mould is the first negative of the process.<br />Step #3: make a hollow wax replica: Molten wax is poured into the mould and then poured out evenly coating the interior walls of the mould. About three coats of wax will make a hollow wax replica of the original sculpture with consistent 1/8" thickness. After cooling, this hollow wax replica is removed from the mould. This wax replica is the second positive in the process. Any surface imperfections in the wax are corrected. For each sculpture to be cast in the edition, separate wax replicas are made. If the edition is 20, then 20 wax replicas will be made from the same mould.<br />Step #4: engineer for the bronze pour: The wax replica is then sprued and gated. This means that a wax pouring cup, wax rods, called "sprues" that will later serve to channel molten metal into the piece, and air vents to release trapped air when the metal is poured are attached to the wax replica. This engineering process is to prepare the piece for the bronze pour. Now an investment, or "ceramic shell", is applied to each wax by dipping it into a heat resistant liquid, or "slurry", and then coating it with a heat resistant sand or "stucco". Each of the 6 to 12 coats must be dry before the next coat is applied. This step normally takes between one and two weeks. This ceramic shell over the wax replica has created the second negative.<br />Step #5: wax is "lost" and bronze is poured: After the ceramic shell covering the wax is completely dry, the piece is inverted and placed in a kiln at 1800 degrees which causes the shell to become strong. The wax melts and pours out of the ceramic shell. Thus the term "lost wax". This empty ceramic shell, the second negative, is placed in a sand pit with the pouring cup uppermost. Molten bronze heated to 2200 degrees is poured into the cup and down through the sprues into the cavities of the shell. As the bronze cools, the last positive is created.<br />Step #6: cool and finish the casting: After a cooling period the shell is broken away revealing the bronze casting. Sprues are cut off, and the sculpture is sand blasted. Any parts which were cast separately are welded back together, and the surface is ground to resemble the surface of the original sculpture. This reworking of the surface is termed "metal chasing" and takes many hours of labour intensive work.<br />Step #7: colour the bronze: The final step is colouring the bronze. The ancient Asians would bury their bronzes to naturally oxidize them, sometimes for years. The colouring is called the "patina". Today the oxidation and colouring can take place within hours. The "patina" is applied by brushing or spraying various chemicals onto the metal with or without heat. Different chemicals are used to create a variety of colours. Often acrylic is used to simulate chemical colours.<br />Steps in making a plaster sculpture. <br />Preparing your sculptural framework: You may simply pour plaster into a box, if you want a block of plaster to carve from. However, for our example we will use a method that is slightly more sophisticated. We will use a human head as out model. Find a picture of a person's head as your starting point. Remember that as this stage we are interested in learning the process of plaster sculpture. Do not be concerned at this stage with creating a great sculptural masterpiece. This can come later. The next step is to build an armature <br />Building an armature: An armature is a frame for your sculpture. It can be made from any strong and rigid material like wire or steel. If you have a small welder you can quickly construct a basic steel frame for almost any sculpture. The frame is a basic rough outline of your sculpture and is meant to hold the material, in this case plaster, securely in place. Use the following method for making your first armature. <br />Secure a round piece of wood to a piece of hardboard. You can do this by gluing the wood together or by using nails or tacks. The length of the wood should be about two or three inches shorter than the length of the head you envisage making. Please note that it is not advisable to try to make a very large sculpture at the beginning. You will find that you may not have enough plaster and that it may be more time- consuming than you at first thought. <br />Now take some lengths of flexible wire and secure them to the piece of hardboard with nails. Bend the wire to make a rounded shape. Attach these wires to the central wooden pole. You should secure at least four pieces of wire in this way. This is the basic structure of your head. Make sure that the entire structure is smaller than the head 's final dimensions. The next stage requires knowledge of the correct mixing of plaster. We will return to the final stage of the armature after the next section. <br />Mixing plaster: Plaster of Paris works though water absorption. The powder from the plaster absorbs the water and develops into a tough, resilient material once it has dried. The relationship between the amount of water and the plaster is crucial when mixing the two. Too much water will make the plaster soft and crumbly. <br />The best method for mixing the plaster correctly is as follows: Take a bucket and fill it to just below half of its depth with clean water. Open your bag of plaster and scoop a handful of plaster. Drop the plaster into the water using your fingers as a filtering tool to ensure that no foreign objects enter the water. You may also use an ordinary kitchen sieve for this purpose; but this is more time consuming and is only necessary when casting a plaster mold from clay. <br />Continue the process by scooping handfuls of plaster and dropping them gently into the water. The process needs to be continuous and you should not stop for a break at this point. Remember that the plaster power is already beginning to react chemically with the water and is starting to " set" or harden. When the plaster starts to form small mounds on top of the water then the correct balance between the water and plaster has been reached. <br />The next step is to gently insert your hand into the bucket of plaster and water and search for any objects, leaves etc. that may have fallen in. Gently stir, searching for clumps of plaster and breaking them up. This process also has the advantage of bringing air bubbles to the surface and ensuring that the plaster is uniform. <br />Finishing the Armature: Now that you have a basic knowledge of plaster mixing, we can complete the armature. Find some old rags and tear then into strips of about 40-50 cm long. Make a mixture of plaster and water. This is only to wet the rags, so fill the bucket only to a height of about 2 inches or 5 cm in depth. Once you have good mixture of plaster and water, dip the cloth strips into the mixture and twist then around the wire support. By winding the wet cloth strips around the armature you are creating a strong support and starting to build the sculpture itself. Allow these strips to dry. Small amounts of plaster like this rarely take longer than an hour to dry, depending of course on the amount of humidity in the air. <br />Creating your sculpture: Once your armature is ready you can begin to " throw" the final plaster shell for your sculpture. As you will be carving into the plaster, you should consider making the initial model slightly larger than the final product. For example, the areas where the nose and the forehead will be situated should be higher than the surrounding areas. Plaster, however, is very versatile and there are numerous ways of building up and carving the final sculpture. <br />Fill the bucket to just under half and begin the process of mixing as outlined above. When the plaster begins to "set" in the bucket- which means when to attain a semi- rigid consistency- begin placing it with your hands, or with any other tool- e.g. a trowel- on the armature. Continue doing this until you have built up the general shape of the head. <br />Carving and adding to the sculpture: One of the great advantages of plaster sculpture is that you can add to the basic shape even after the plaster has dried. This means that if you decide that the nose of your sculpture should be larger, you can simply mix some plaster and add this to the nose. There are some things you should know before adding to the sculpture. Plaster will not adhere well to plaster if it is too dry. The best method of adding plaster to plaster is to firstly cut grooves into the dry plaster. This helps the adhesion of the next layer of wet plaster. <br />Secondly, it is a good idea to wet the surface dried plaster, as this will also create adhesion. Some sculptors also apply cold glue or white glue to the surface of the dry sculpture. Ideally you should not wait for the plaster to be completely dry before finishing this process. <br />Once you have the rough shape of the head, you can begin carving the final form. Carving into plaster is extremely easy when it is still slightly wet. The plaster becomes harder within a few hours and, depending on the consistency of your original mixture, can become almost rock hard over a period of days and weeks. The ideal time is to begin carving is about three hours after the plaster has begun to set, i.e. get hard. <br />There are numerous sets of basic carving tools that can be bought at craft shops. These sets are usually intended for woodcarving, but are ideal for plaster. On the hand, you can use almost any sharp instrument to carve plaster. Carve into the soft plaster and determine the main areas of your face first. In other words, carve out the nose, mouth, check bones, eyes etc. Once your plaster hardens you can refine these areas more easily. Remember that if you find that you have not added enough plaster to your armature you can always add small amounts of plaster, using the method suggested above. <br />The final product: Now that you have carved your masterpiece, there are a few things that you should consider. Plaster is not intended as an outdoor medium for sculpture. Although it is comparatively strong and resistant, it is can weather fairly easily if left outdoors for a period of time. However, plaster can be kept indoors and, as long as it is not thrown about, will last for years. <br />Sculptors usually use plaster models as an intermediate stage in the development of their art. These plaster sculptures are then cast into a more durable material like bronze. But there are many sculptors, including Picasso, who retained plaster sculptures in their original plaster form. As a final touch you can use any clear vanish to protect the sculpture. <br />