 |  | Small-Scale Horn Processing (ILO - WEP, 1988, 104 p.) | ||
 |  | CHAPTER IV. SHAPING | ||
|  | 1. General | ||
| | 2. Heating | ||
| | 3. Straightening | ||
| | 4. Opening the hollow section | ||
| | 5. Flattening the hollow section | ||
| | 6. Bending and folding | ||
| | 7. Stamping | ||
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Heating makes horn malleable for purposes of curving, folding and stamping. These operations still present difficulties, however, as horn, even when well heated, remains fairly resistent to shaping. It still has a tendency to revert to its original shape. Consequently, horn products should not be washed in hot water, especially long pieces such as salad servers, ladles, spoons and so on.
Among horners the most common method of heating horn is over a fire, particularly a wood fire which produces long, wide flames that cover the horn. Moreover, wood is plentiful and cheap even in the remotest parts of the bush. A candle flame may be used for heating small pieces. Gas or hot air are used in modern workshops. Small finishing touches may be made over the fire, after the horn has been polished. In this case, the horn should be held away from the flame, though this lengthens the heating time. Horn should be heated and shaped before polishing, as exposure to flame causes the keratin to sizzle and the surface to spoil. Experience has shown that little damage is done if the horn is kept moist throughout heating by being immersed in water at regular intervals. The section of horn to be shaped should be run lightly and continuously over the flame, as shown in figure IV.1. Prolonged holding of horn in the same position causes overheating which spoils its texture and appearance, even after polishing.
Figure IV.1: Heating a
horn
Horns are naturally curved and straightening may be necessary for the manufacture of certain objects. To straighten a hollow horn section, it is first necessary to fix it while still hot to a post set securely in the ground and to pull or push it in the opposite direction to the curve (figure IV.2).
Figure IV.2: Straightening a horn
attached to a post
The solid horn section can also be heated and straightened by pushing it laterally by hand, the unheated hollow section being held securely in a vice (figure IV.3). To prevent the horn from bending in the opposite direction as a result of the hand pressure while it is being straightened, the straightened section is made rigid by moistening it with water. The horn tip is straightened by being heated and tapped with a wooden mallet.
Figure IV.3: Straightening a horn
held in a
vice
To flatten a hollow horn, it must first be opened by a cross cut (figure IV.4) at the point where the side of the hollow section becomes thicker. The cut is made not across the entire width of the horn but only up to the inner surface of the hollow section. A longitudinal cut is then made (figure IV.5) along the entire length of the hollow section.
Figure IV.4: Cross cut
Figure IV.5: Longitudinal cut
The hollow section is heated on both sides of the longitudinal cut. The opposite side of the hollow section must remain straight and rigid when the horn is opened. When the heated section of the walls has softened, the horn must be placed on a post fixed firmly in the ground or on a spindle held in a vice and pushed, as shown in figure IV.6. The hollow section will now open easily. Care must be taken to see that the horn is hot enough to be malleable as the hollow section will otherwise crack and be unusable.
Figure IV.6: Opening the hollow
section
Once the hollow section has been opened, the wall is flattened while still hot by being pressed down with the foot (figure IV.7) or tapped with a wooden mallet. Flattening is completed by placing the horn, while still hot, in a wooden vice and/or tapping it with a wooden mallet.
If the hollow section is to be flattened for the manufacture of buttons, spoons, and so on, whose width is less than half the circumference of the hollow section, the horn should be cut as indicated in figure IV.8. It will then be easy to flatten the two hollow section halves by heating them and gripping them tightly between the jaws of a wooden vice.
A small piece of horn may be curved by hand by heating it, as shown in figure IV.9.
Figure IV.7: Flattening the hollow
section
Figure IV.8: Cutting the horn
For bending, a candle flame (figure IV.10) provides a pin-point source of heat which enables the radius of curvature of the bend to be reduced to a minimum.
Figure IV.9: Heat bending
Figure IV.10:
Folding
To stamp a flat piece of horn it must be heated until it is soft and clamped firmly between a stamp and a die of the required shape.
This technique may be illustrated by a specific example. Stamping is most commonly employed by artisans for shaping the hollow part of a spoon (see figure IX.4). Figure IV.11 shows a rough model of a spoon made from flattened horn. The flat end is to be stamped to form the hollow of the spoon.
Figure IV.11: Outline of spoon cut in
flattened horn
Figure IV.12 shows an adjustable vice which can be used as a stamping press. A stamp and die (figure IV.13) are mounted between the jaws of the vice (figure IV.14). The convex form of the stamp must be exactly the same as the inner shape of the hollow part of the spoon to be made, while the concave form of the die must be equally identical with the external shape of the hollow part of the spoon. Two sliding lugs are used to align the stamp and die correctly during the stamping operation. To be stamped, the flat end of the model simply has to be heated to soften it, then gripped tightly between stamp and die. When only a small number of objects is required, the stamp and die used may be cut in hardwood such as rosewood. For larger batches, the stamp and die should be made of a material that is more resistant than wood, such as sand-cast aluminium alloy. This technique may be used readily in certain countries where a large number of artisan-founders manufacture kitchen utensils (pots, plates, ladles, spoons, etc.) from aluminium scrap. Other objects can be made on the same principle, from flattened horn, all that are needed being stamps and dies of the required shape.
Figure IV.12: Adjustable vice
Figure IV.13: Stamp and die
Figure IV.14: Mounting stamp and
die
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