The techniques discussed below describe the manipulation and treatment of wrought iron, using explanations and descriptions of the methods available from the early days of blacksmithing. Many of these are still employed by present day blacksmiths who prefer to use the purest traditional means of creating examples of wrought iron.
The Forging of iron on the anvil with the hammer achieves the most satisfactory results, when the metal is heated to a bright red. Small pieces are forged by a single workman; larger ones require one or more 'strikers' or assistants, who strike the metal at alternate intervals with a hammer. This aids the blacksmith in working a piece of wrought iron, with less time and loss of heat and helps to prevent physical exertion and fatigue. The red-hot iron is cleansed from cinder by knocking it on the anvil and giving it a few light taps with the hammer; neglecting to take this precaution may cause the cinders to be worked into the metal. If the latter is to become hard and elastic the forging continues until the iron cools. 0bjects that have become too hard are annealed, (i.e. reheated to a faint red and allowed to cool gradually). Welding, (i.e. the forging of two separate pieces into one), is done under strong white heat. Both pieces must be equally hot, and the parts to be welded must be as clean as possible; for example by using arenaceous quartz, borax, or some other substance to prevent oxidation. At first the striking should be quick, light, and then gradually heavier, proceeding from the middle outwards, so that the slag may be thoroughly driven out and uneven spots be prevented. Welding by overlapping naturally, forms a better junction than butt welding in which the ends are only brought together: this is one of the reasons why the parts should be prepared (as described with the substances mentioned above), spread out, and thinned, prior to the actual joining. The welding together of iron and steel,(which takes place principally in tool making); is called steeling, and requires great care and using of a special welding powder.
Flattening or taking down is equally necessary for lengthening or widening an object. The blows given with the narrow edge of the hammer are more effective than those with the broad face. The grooves wrought by the former are smoothed out by the latter. Upsetting, or jumping is the exact reverse of flattening; it means both thickening and shortening. It is effected by striking the red hot piece on the anvil or on a special jumping-block, or by hard hammering on the end. Bent or twisted pieces are straightened to the right shape. It is generally done with the hammer on the anvil, but sometimes a special straightening-plate is used; the process may be effected in either hot or cold state. Flattening, jumping and straightening require a certain dexterity in handling which is not easy to describe.
Bending may be done warm or cold. Bending at right angles is done by hammering over an edge of the anvil, or the square part of its beak, or with the aid of a vice. Curves are produced on the round end of the beak or on a conical mandrel. In curved bends a scroll-horn is also occasionally used. This is a tool which is fixed into the vice and has two cylindrical prongs forming a fork. For spiral windings and other forms which occur frequently in art smithing, special scroll tools, pins, around which the object is twisted, are used. These tools have the same form that the piece being handed is to take; the latter is generally of thick flat iron. Large flat curves are produced by placing the iron on two raised and separated supports and striking downwards in the middle. Sheet iron is best bent and turned over on bending and tilting machines.
Embossing is the punching out of rounded bumps called "bosses". The iron may be 'bossed-out' when it's red hot by driving it into a suitable cavity or swage. Bosses are produced by hammering the iron when cold, with suitable ball hammers, upon an under-layer of wood or lead. Large flat domes are obtained by hammering out the sheet-iron gradually and from the middle towards the edge. In finer work small bosses are produced by means of a special instrument, called a snarling tool, and is made fast in the vice or onto a special block. By striking with the hammer near the fixed end of the tool, the arm vibrates; and its bent striking end produces by the percussion produced when the bosses in the metal are exposed to its blows. The upper part serves as a gauge for ensuring that the bosses are formed in the right place.
Impressing sheet iron into hollow and rounded forms, is effected with the lathe by tool pressure. Punching is done with similar tools, which are short rectangular steel bars, with the edges taken off and tapered towards the point, which can be found in many shapes. Small bosses can be made with them and the punching-hammer in sheet-iron, as well as bead-like or ribbed surfaces. Where as thin sheets are generally punched from the back so that the bosses appear in relief. With thicker sheets, this detail is achieved by indenting the metal with punches or chisels.
Engraving consists in cutting flat, mostly linear , designs in the surface of the sheet by means of a 'graver', or 'graving-tool'. This is generally done using hand pressure; and when the work is heavier, with the aid of a hammer. When the hammer is used, and especially when curves are made; it is called 'cutting in iron'.Cutting in iron...iron cutting, engraving and chasing, is the finishing off of cast or hammered parts either with the graver, the use of punches or other tools, and are usually only used in working wrought iron in small artistic objects. These constitute an art in themselves and are rarely performed by the skilled smith or even locksmith.
Etching is effected by means of acids. The sheet is first covered with a layer of protective wax, asphalt, or some suitable varnish. The parts to be etched are then deprived of the protective agent and the acid eats into them to the desired depth. Where the surface which is not to be etched is smaller than that which is to be affected by etching, the reverse operation sometimes occurs, i.e. the protecting material is painted or otherwise applied on the necessary places only. When the acid has acted on the metal enough, it is cleaned off with turpentine. Etching is principally used to ornament smaller artistic objects. Sometimes the etched parts are color-varnished so as to give the effect of 'Niello', or Enameling.'Niello-Work' means that the metal is engraved with the same technique used in copper-plate engraving, and that the parts cut away; are filled with a substance comprised of sulphur, silver, copper and lead. In melting in the niello compound, the metal must not be made red-hot or it will waste and become 'holed'.In Inlaying or hammering metal, such as gold and silver on iron, the parts receiving the inlay need a dove-tail cut (wider at the base than at the surface, which is a shape that is produced with a chisel; into which the softer metals are hammered. A simpler and cheaper, but also less durable way, is to 'hatch', and to cut-in lines with the graver, and hammer the precious metal onto the roughened metal. The unembellished parts are made smooth afterwards.
Enameling, (i.e. the melting of vitreous paste onto the metal), was almost exclusively applied to cooking utensils, bathtubs and sinks, or advertisements, and was mostly used for practical rather than artistic purposes. Completely smooth and bright surfaces are produced by planing, grinding, and polishing.Planing is done using a plane, which is fabricated in various forms, but must always have a perfectly sharpened edge. The elevations to be removed are more easily detected, by moving the metal being manipulated; backwards and forwards on a perfectly level, painted straightening-plate.
Grinding is performed, either by using a hand-grindstone; or with wet or dry revolving grindstones. Pumice-stone, emery-paper or cloth, emery-powder or iron-scale, are also used with oil; on wood, leather or lead.
Polishing gives the object a high-degree of smoothness referred to as 'glint'. Is is produced by continuous friction with fine powder, that is polished by using soft leather or wool that has been moistened with spirit or oil. Lime, rotten-stone, putty powder, and serve, among other things, as polishing powder. Burnishing tools and agates are also used; these also serving to press-down any inequalities in the metal. The shapes of the steel pieces, which are set in wooden handles, depend on the work. Round or cylindrical shapes yield the best results when polished on a lathe.As wrought iron and steel easily rust under the influence of the air, especially when exposed to moisture and water. The surface is protected sometimes by means of applying other metals, or by bronzing, blackening or tempering, and also by coating it with varnish or oil-color. In every one of these processes, first a thorough cleansing from scale needs to be performed, and a metallically pure surface must be obtained. In order for the result to be successful, rust must not be allowed to set in beneath the covering material. This is done by pickling or removing the surface with diluted sulfuric acid; reheating the metal, or by brushing and scraping. A coating of lead, zinc, tin, copper, brass, nickel, silver or gold may be deposited either by "dry process", in which the metal pieces are dipped red-hot into the molten metal. An alternate "wet process" method, in which metal pieces are dipped into liquids that contain the metals and chemicals in a solution necessary to effect their union; through precipitation by galvanization; or by 'plating' in which the covering-metal is pressed or rolled on to the wrought iron in the form of thin sheets or plates. Gilding, namely mercury gilding; is used to produce artistic enameled iron ware, in which gold in amalgam with quicksilver is laid on; and the quicksilver is evaporated by heat.Leaf-gilding, is the process in which gold-leaf is pressed onto a prepared and roughened metal surface, and polished with a steel burnisher, or other traditional methods.Browning or bronzing involves creating an artificially oxidized surface, the oxide protecting the metal from further rusting.
Blackening consists of smoking the article over a fire of resinous wood, and then brushing is done; or, the articles are smeared with linseed oil, and then burnt off in the forge.
Varnishing is done with a transparent mixture of linseed oil and turpentine that is used to protect uncovered surfaces. 0iling, or smearing with tallow may be substituted. Varnishing with iron, asphalt, tar-varnish, or coating with oil-color; is chiefly confined to coarser articles having less carefully worked surfaces, or to objects that are exposed to the weather. Before the actual process of applying these substances occurs, a 'ground coat', consisting of lead paint or graphite; is laid on. Decorative effects were sometimes produced by polychromatic treatment, more recently; attempts have been made to revive this process.
This article is an edited version of the original text from "A Handbook of Art Smithing" .