Silversmithing and jewellery introduction to techniques and tools
SILVERSMITHING


Silversmithing and jewellery

by

Brian Allensby ©

Using original sketches


With insipration from Alan King, Keith Smith and Paul de Lamerie


Silversmithing and jewellery making have usually come under the elementary heading, of beaten metalwork, as indeed some of the processes are but not all, so this correct heading is being used here.

The materials used in silversmithing are chosen for their malleability and ductility. Owing to the high cost of silver, copper and gilding metal are often used as these can then be silverplated if required. Brass is used when its colour is important, but when it is annealed it is too hard for most hollowing processes. Pewter and its more modern counterpart Britannia metal, which contains no lead, is is more expensive than copper and presents difficulties with its low melting point when soldered. Aluminium too presents difficulties in soldering, and is therefore more often used in thin sheet or cast form. The chief gauges involved are from 14 swg (2.032mm) to 26 swg (0.457mm) although 20 swg (0.036mm) for domestic articles and 22 swg (0.711mm) for jewellery are commonly used.

Tools and Equipment


Many of the tools and equipment require will be in general use in the workshop, but a few are kept specially for silversmithing.

Acid Bath
For the cleaning and removal of oxides a solution of ten parts water to one part sulphuric acid in a container made of stoneware or lead is used. The container may be heated or not. For small work a Pyrex dish may be used. In all cases a lid should be fitted to the top of the bath to prevent splashing and a sink with running water should be adjacent. Heated baths should have their fumes extracted by a fan. When mixing a solution for the bath the acid should always be added to the water. Copper or brass tongs or a nickel basket must be used for holding work in the acid.

If iron, or a different metal to that which is being cleaned is put in or left in the pickle, plating of the surface of the metal being cleaned will occur.

Hammers
A number of hammers made from forged cast steel in sizes ranging from 0.11 kilograms (4 oz) to 0.28 kilograms (10 oz) and with various heads suitable for different operations are available. The faces of the hammers should be kept polished, clean and free from marks or damage to work will result.
Hammers and Mallets

Hammers and Mallets



Stakes
Many stakes are available and special purpose ones can be made, but all must have highly polished and unmarked surfaces if good work is to be achieved. Stakes may be held in a socket, vice or in the case of the stake heads in a horse.
Raising Stakes

Raising stakes


Stakes

Stakes



Blocks and Sandbags
Hollowing blocks consist of various sized hollows gouged out of an elm or beech tree trunk or a 152mm (6") block, the block being more convenient as it can be held in a vice, whilst the tree trunk stands on the floor. Sandbags are leather bags filled with sand in sizes from 102mm. (4") to 254mm (10").
BlockSandbag

        Block                            Sandbag



Jewellers Snips
These are obtained in the straight or bent pattern and are 178mm (7") in length and light in weight.
Jewellers Snips

Jewellers Snips



Repoussé and Matting Punches
These punches are used for decoration, the Repoussþ punches producing a plain finish.
Repoussé punches

Repoussé punches



Processes

Hollowing or blocking
This is a method of shaping a flat disc, of the required diameter, into a shallow, dish or bowl in a hollow in a wooden block or Sandbag with a round ended bossing mallet or Blocking hammer.
hollowing

Hollowing

When the disc has been cut the burrs on the edges are removed with a smooth file or paper, thus preventing injury to hands and also preventing the small burrs from breaking off, entering the mallet face and damaging the surface of the disc when stuck. The disc should then be softened by a process known as annealing, which by raising the temperature of the metal, the deformed grains recrystallise into new undistorted grains, thus restoring it to a soft and ductile structure. This is carried out on a revolving hearth with a blowpipe. The disc is revolved slowly and a bushy flame slowly and uniformly warming the metal until it is dull red at 650ºC

The work is them allowed to cool slowly, as sudden quenching in water could alter its shape, although in the early stages of forming quenching in water can be permitted. The oxide and impurities are then removed by pickling in the acid bath. The disc is then removed with tongs or basket from the acid and washed thoroughly under running water, cleaned with pumice powder and brush, then dried in sawdust. All work must be cleaned after each heating or the oxide and the impurities on the surface will be hammered into the surface of the metal and a good final finish will not be achieved.

The disc should then be placed on the block or sandbag with the centre the on the underside. The top should be marked with a pencil line from the centre to the outside and a number of concentric circles drawn with a pencil compass to act as a starting radius line and guide lines when hollowing.
Hollowing

Guide lines

The disc is then tilted so that the nearside is in the hollow of the block and struck with the bossing mallet or blocking hammer about 10mm (3/8") from the near edge. The disc is then turned until a full circle has been achieved and then the next circle is commenced until the middle has been reached. If crinkles or buckles are formed at the edges these should be hammered out as they appear. When the work becomes work-hardened through repeated hammering or the centre has been reached the metal must again be annealed or cracks will appear. This process is repeated until the required shape is achieved and is the preliminary preceding process to raising.

Doming
Hollowing very small work such as the legs of small articles and for the decoration of jewellery is carried out using a brass doming block which consists of a number of different sized concave recesses into which fit tempered steel or wood punches. When the domes are required to be cut from the sheet they are cut with a cutting tool punch.
Doming

Doming



Sinking
A similar process to hollowing except that hammering does not start at the periphery but a measured distance in leaving a flat rim.
Sinking

Sinking

To commence the disc is marked out to the width of the desired rim and the depth of recess. Annealing then takes place as in hollowing. Next the sinking block is placed in a vice and the horizontally held metal sunk into the shape on the wood with a Bossing mallet or Blocking hammer whilst being held in place and rotated with the other hand. If a circular article is being sunk two pins may be placed in the wood block to help guide the flat surface of the rim. The rim and the base surface are kept flat with a small mallet or by placing each surface in turn on a surface plate, placing a piece of wood on it and striking it with a hammer. When the true shape has been obtained the article is now annealed and cleaned and is ready for planishing.

Raising
Unlike hollowing, which only allows for shallow shapes, raising is the traditional method for obtaining taller shapes, without a steam, by striking the metal on its outside instead of its inside. The tools used are the raising stake, which may be purchased ready made or made from mild steel which is then polished. A 0.25 kilogramme (8 oz.) raising hammer with all its sharp corners rounded, and polished, and a hardwood mallet. In modern workshops lathes for spinning (fig 439) have superseded raising for repetitive articles which are then finished by hand. Work which is usually a disc for a circular shaped article is first annealed and cleaned and subsequently annealed and cleaned after each raising or course. The disc is then slightly hollowed and then marked out with concentric pencil circles. The hollowed disc is then placed against the stake so that the end of the stake is at the back of the line at which you wish to commence. The metal is now struck with the raising hammer making sure that the toe of the hammer gets well down (fig 260).
Raising

Raising

It usually takes three blows before the click of the metal is heard and the metal can be rotated. The process is then repeated until a full circle is completed. Continue the process until within 6mm (1/4") of the top and finish the last coarse with a boxwood or hide mallet as the edge may be showing signs of waving and if struck with hammer it may stretch. Subsequent raisings are now carried out until the desired shape is achieved. If the sides tend to become concave raising should be commenced further up the side, side, starting with light blows or a ridge will appear. This should be continued until the shape has been put right. If the work tends to have only one side concave raising should be concentrated on that area until it has been removed. The article will now require planishing and then the base flattened on a bottoming stake with a mallet. The article will now require planishing and then the base flattened on a bottoming stake with a mallet. When the base is quite flat the article should be placed on a surface plate, tested with a try square to see if it is upright and then a line scribed round the top with a scribing block. Any unevenness is then cut away with snips. The edge may then need thickening or caulking after which it will need rubbing down on a flat stone or emery cloth held on a flat surface.

Snarling
This method of hammering from the inside is used when a tall raised form or a narrow necked job requires its body truing up or filling out. The operation consists of positioning the job on the head of the snarling iron, striking the arm of the iron with a hammer, so that the head rebounds against the inside of the job. After each blow the job is rotated to its next position and the iron struck again until the desired shape is achieved.
Snarling

Snarling



Caulking
To strengthen the edge of sheet metal it is thickened by hammering on its edge. This then adds to the natural thickening of the raising and gives a tapering thickness. The edge of flat sheet is thickened by placing the sheet between folding bars and hammering the edge with a collet hammer whilst other shapes are held on a sandbag. Work should be caulked before annealing or after it has work-hardened otherwise buckling can result.
Caulking

Caulking



Planishing
This is the finishing process which trues the shape of the article, no matter how it was formed, and removes all the previous working marks from the surface. The tools required are a planishing hammer with one domed and one flat polished face, a collet hammer for concave surfaces and a number of suitable highly polished stacks. The work to be planished should first be annealed, cleaned and polished. Concentric circles are then drawn 5mm (3/16") apart on the surface with a pencil compass to act as guide lines. A stake with a slightly smaller radius than the article being planished should than be got ready and the article placed on it. The planishing hammer should then be paced on the article, thus holding it in position on stake. To start planishing the free hand firmly holds the article and will after each tap of the hammer rotate the article. The hammer is then lifted and the surface of the article is lightly struck with a wiping motion, which will produce a clear ringing note, thus indicating a true contact with the stake. The hammer must rise and fall constantly over the same spot on the stake, whilst the work is rotated, and then small or large facets will be produced depending on the weight of the tap. Starting from the centre, each circle of the guide lines should be planished in turn, each facet being of uniform size should overlap the previous one and the one on the preceding row.
Planishing

Planishing

When the whole surface has been completed it may be necessary to planished it two or three times to remove all traces of marks. If a cylindrical article tends to have a concave side surface lateral planishing is carried out. On completion of planishing the facets are buffed out unless they are to remain for decoration. In the process of planishing the metal is hardened, stretched and thinned. Its prime object is to smooth and true the article, not to decorate it, although the facets look attractive on some articles.

Seamed Work
Further articles and attachments, for raised articles, may be made by developing them from a flat sheet and seaming them with solder.

Box making
First the shape of the required rectangular box is developed on the flat sheet and cut out. Next the joints are prepared by filing or scraping to an angle of 45ºC and the sides are then brought up, forming nice sharp corners.
Box deve;pment

Box development

The box is then then wired, and the seams fluxed and soldered. If the box is to have a base and a lid of the same shape a sheet is made to fit the open side of the box. Before the sheet is fitted, wired, fluxed and soldered, the previously soldered joints should have an application of jewellers rouge and loan to prevent them running.

A corner slot is cut, with a brass backed saw, on a line where the lid is to be cut off,
Box lid cutting

Box lid cutting

thus allowing the air to escape when it is soldered. When the box is complete it is then sawn through, thus giving a lid and a base. The base is usually the sheet that has just been soldered in. The edges are then thickened and strengthened by soldering strip to them.
Box edge strengthening

Box edge strengthening



Drawn wire and tube
This is a method of reducing the diameter of wire or closing a tub by annealing it and pulling it through a series of shaped holes in a draw plate held in a vice or on a draw bench.
Tube drawing

Tube drawing

Tube drawing

The object to be drawn should be tapered and placed in the first lubricated hole in the draw plate and pulled through with tongs in each successive hole until the required diameter is achieved. If a tub, or chenier for hinges is needed a strip of metal approximately three times the diameter required is first creased and then drawn to close it. Hinges are made by fitting short lengths of chenier with their seam in contact with the metal surface to which they are to be soldered.
hing Tubes

Hing Tubes



Decorative wires
Many beautiful and interesting patterns can be by twisting strip or wire of various sections and thicknesses held in a vice at one end and twisted with a hand drill at the other. The twists can be used as handles or mouldings which are soldered on to an article for decoration.
Twisting

Twisting

By bending wire or section round jigs made from wood and steel pins or nails may more decorations can be made. Wires can also be used singly for decoration and as strengthening edges.
Bending

Bending



Spouts and irregular shapes
To produce a spout, hollow handle or a handle mounting a shape is developed, shaped, seamed and planished. It may be fitted by placing a piece of emery paper on the surface to which it is to fit and rubbing the matching fitting surface on it until a good fit is achieved.
Spout

Spout



Settings
A many semi precious stones can be purchased for a few new pence, a number of simple settings are shown here, the most simple being the bezel, which consists of a thin strip of metal fitted closely to the stone to be held and then soldered to the desired object, cleaned and polished. The bezel is then pushed against the side of the stone to hold it firmly in place.
Settings

bezel

Settings and Bezels



Jewellers findings
A fastening is usually required to hold jewellery in place and being referred to as a finding this may be made or purchased ready-made.
Findings

Jewellers Findings



Decoration


Repoussé and chasing
Repoussé is basically the forming of high and low relief with punches, from the back of the metal, whereas chasing is the, defining and texturing of the metal with punches after the Repoussé relief is finished. The metal to be decorated is supported held in a pitch mixture supported in a tray or a hemispherical bowl, which, if supported in a circular ring, allows it to be worked at all angles. Light gauge metal may be punched if placed on a sheet of lead. The pitch mixture must be firm enough to support the metal and yet resilient enough to allow the metal to be driven into it by the punches. The mixture is prepared by melting 14 parts of Swedish pitch and slowly stirring in 1 part of tallow with 14 parts of plaster of Paris. Before the work is paced on the pitch for working, it should be lightly oiled to facilitate the eventual removal by warming with a blowpipe and cleaning with a rag dipped in paraffin.

Many cast tool steel punches which are hardened and tempered are available. Special ones may be made and they are tapped with the broad face of a Repoussé hammer.
Repoussé punches

Repoussé punches



To commence, the design is transferred from your previously prepared drawing to the work by means of Keil or carbon paper and the resulting lines are lightly scribed.

The work is then inverted and placed on the pitch and the design embossed the back.

The design is usually started with a tracing tool which is held at an angle to the work, so that when it is tapped radially it moves towards the worker, making a smooth indented line.
Chasing

Chasing



To sharpen up the design the work can then be reversed and the face chased with tracing punches. Texturing can be carried out with the many matting and individually made decorative punches.

Engraving
This is the decorative cutting of the surface of the metal with a tool steel graver. Many gravers are available, but the most used is the square graver which is angled so that its handle fits comfortably into the palm of the hand (fig 275). The graver is shaped and sharpened so that it tends to raise the handle when it is run parallel over the surface of the metal. Sharpening should be commenced on an Indian stone and finished on 000 blue black emery paper held on a flat surface.
Graver

Graver



The surface of the metal to be engraved should be polished. The design to be transferred should be traced, then Plasticine rubbed on the back of the tracing paper. The paper is then placed on the surface to be engraved and the design transferred with a blunt scriber.

To commence engraving, flat work is held on a sand-bag and the work rotated on this with only, a slight movement of the graver, away from the worker.
Engraving

Engraving



Etching
Etching is a process by which the surface of a metal may be decorated by the controlled eating away by acid of areas of its surface not covered by an acid resist.

Acid mordants
Many acid solutions may be used and the following are a suitable selection for the metals named. A “Pyrex” or polythene container being used for an etching bath although a wall of wax round a small area to be etched is sufficient. The work should be laid sloping face down and prevented from a touching the bottom of the bath by means a string cradle in order that the sediment falls away.
String cradle

String cradle



If the surface is laid face upwards gentle brushing with a feather should be used to prevent the sediment and bubbles forming.

Gold (18 k. or lower)

Hydrochloric acid 8 parts
Nitric acid 4 parts
Iron perchloride 1 part
Water 40 parts


Silver, iron and steel

Nitric acid 1 part
Water 3 parts


Aluminium

Iron Perchloride 1 part
Water 1 part


Copper, gilding metal, brass

Iron perchloride 3 parts
Water 1 part


Metal Preparation
The surface on which the acid resist is to be attached must be thoroughly cleaned of all grease and oxides. A fine pumice powder and water, to which a few drops of ammonia have been added, is used for the cleaning. The work is then thoroughly rinsed.

Resists
Various acid resistants, consisting of wax, vegetable gums and asphaltum, are available, each being suitable for a particular job.

Wax
Work can be dipped warm into molten beeswax, then the part to be decorated is removed with various etching needles.
Etching needle

Wax removal by etching needle



After etching the wax is then removed by heating the work and wiping off, or dissolved off in benzine or acetone. Wax pencils may be used for stopping out lines not required.

Stopping out varnish
Various recipes are available for making varnish, or it may be bought ready made. The two basic types contain either asphaltum powder or shellac mixed with turpentine or methylated spirit respectively.

Stopping out varnish is used for protecting 'parts not to be etched by the acid; round the design, on the front edges and back. The edges will require two coats as the varnish tends to creep away from them. The varnish takes several minutes to dry and, if placed in the acid wet, under biting will occur. Several methods of decoration can be achieved with varnish. The first is by means of dripping and trailing a treacle consistency varnish over the surface to be decorated. The second is by painting round the lines of a previously transferred design. The third method in which the design is first painted on with a slow-drying substance known as lift ground made from equal parts treacle, gum Arabic and “Isinglass” in a small amount of water.
Lift ground paint

Lift ground paint



Then all this is covered with the stopping out varnish.
Stopping out varnish

Stopping out varnish



When the varnish is dry, the work is placed in warm water and the surface stroked with cotton wool. The part painted with lift ground will then come away leaving the design ready.
Lift ground paint removed

Lift ground paint removed





Solid ball ground
Being made into the shape of a small 50mm round ball the ground may be bought ready-made from 2 parts beeswax, 2 parts asphaltum and 1 part pitch (Swedish or Burgundy). If made, the wax and pitch are melted in a saucepan, stirred and the asphaltum added. After 20 minutes the is poured into warm water and rolled into the appropriate sized balls. In use the ground is placed in a piece of fine cloth and the ends brought up and tied to form a handle thereby forming a dabber.
Dabber

Dabber


The previously cleaned work is then warmed, the dabber rubbed on the surface and rocked in a, circular motion. The work is again heated until a glazed even unburned deposit is formed. The edges and back are then painted with an acid resist. Etching is by needle.

Transferring the design
The design is traced from the original, secured with adhesive tape to the surface to be etched. Carbon, or better still red Keil paper, is placed between the two surfaces and the design transferred by using a pencil which will leave a fine line.
Design transfer

Design transfer



The design is then painted in with the acid resist.

Enamelling

Enamelling dates back 3500 years when the Egyptians started using it for jewellery decoration.

Enamel is a fusion of glass on metal background and should not be confused with household synthetic paint.

Composition and manufacture
The base of jewellery enamel is a clear glass flux called “fret” l which consists of silica, red lead oxide, (soda) and potassium hydroxide. The amount of lead and potassium hydroxide determines the degree of hardness and brilliance of the enamels. The colours are obtained by adding varying proportions of metallic oxides and opacity is obtained by the addition of oxides of lead and tin.

Four main types of enamel one produced: opaque (not seen through), transparent (seen through), opalescent (rainbow reflections) and translucent (allowing the light to pass through). Aluminium enamels are available but due to their low melting point few colours are available.

Steel enamels are basically composed of borax, feldspar and quartz with antimony, titanium or zirconium added for opacity.

The enamel is produced by smelting the constituents in a fireclay crucible at 1150ºC to 1250ºC and pouring it out to form cakes on metal slabs. The cakes are then crushed and ground dry.

Preparation of Enamel
Enamel frit is supplied in either cake form, crushed and washed, or ground ready for use.

Cake form
The irregular 12mm (1/2") thick cake should be crushed by means of a mortar and pestle.
Pestle and Mortar

Pestle and Mortar



until it passes through a 60 mesh. The frit is then washed to clean and separate the frit particles. This is done by allowing a tap to run slowly onto a dish containing the frit and as the action progresses the milky consistency will clear. The frit is then dried.
Wash enamel

Wash enamel under running water. Drain off and allow to dry.



Crushed and Washed
Purchased crushed, this enamel is suitable for decorative effects when fired onto enamelled surfaces.

Ground
Opaque enamels ape obtainable to pass through a 60 mesh and transparent enamels to pass through a 30 mash.

All enamels should be stored in air-tight jars or decomposition takes place and shows itself as white flakes. Transparent frits are especially susceptible and are left with milky and pitted patches after fusion.

Metals for Enamelling

Copper: This is the ideal base as it is easily shaped.

Gilding Metal: 90/10 composition is recommended, but not more than two firings are recommended or the zinc will burn out and discolour the enamel.

Silver: Fine silver or enamelling silver should be used and several firings should be avoided if possible.

Gold: Enamelling gold is available, but much use is prohibitive due to the price.

Aluminium: New developments are coming about in this field, but at the moment there are limitations.

Steel: Enamelling steel is recommended, but mild steel can be used, although copper heading or blistering may occur.

Preparation of the metal

To ensure adhesion of the enamel to the metal the oxides and greases must be removed from its surface.

Non ferrous
Degreasing is carried out by heating the job to a dull red 800ºC and plunging in water, thus removing the scale by this action. The job is then placed on a clean surface and any remaining scale is removed with pumice power and then washed. For high class work the metal should be pickled to a clean bright finish by immersing in 10% sulphuric acid for 10 - 15 minutes and then washed thoroughly in hot water.

The fingers should not be allowed to touch the surface any during any operation or fusion of the enamel will be prevented.

Ferrous
To remove the oil from the surface of the steel it can be wiped with a paraffin rag, scrubbed with pumice powder, rinsed in water and dried with a clean cloth. A better method of degreasing is to anneal the steel at 700 - 75ºC for 3 to 4 minutes, then pickled for 20 minutes in a 10% hydrochloric acid solution until it has a clean, light grey, etched surface. Washing in hot water is followed by neutralising the acid remaining on the surface by washing in a 1% solution of sodium carbonate. Finally wash thoroughly in hot water and dry, being most careful to avoid handling.

Gum preparation
Gum Arabic or tragacanth is used to attach the enamel to the metal surface as this does not leave any deposit when heated. To prepare, first take 14 grams (1/2oz) of gum tragacanth and mix to a creamy paste with methylated spirits. Add the mixture to 1 litre (1 quart) of cold water and allow to stand overnight.

Application and firing
Enamel can be applied to the surface of the metal in a number of different ways each depending on the effect and decoration required on the end product. The following methods are intended as an introduction to these techniques.

Non ferrous metals
A coating of gum should be brushed on the surface the previously prepared clean surface of the metal with a camel hair brush.
Paint surfaces

Paint all surfaces to be enamelled with gum tragacanth

The powdered enamel should be evenly dusted onto the surface and edges of the metal by means of a sieve, made from 60 or 100 mesh phosphor bronze lawn.
Dust enamalr

Dust the enamel evenly on the work held in a clean tray

The job is now ready for firing. A sieve can be made from a screw top coffee jar or bay food jar, by cutting a hole, with a 7mm (1/4") margin round the edge of the screw top and placing the lawn within the top.

Ground coat
First an even first coat should be applied by dipping and rubbing it onto the surface of the steel and leaving it to drain from one corner. The ground coat is usually supplied in a liquid form and can be thinned with water. This is now ready for firing in the muffled furnace for 3 - 4 minutes at 840º - 850ºC.

Cover coat
This coat should be applied by pouring the liquid enamel on one side of the job until the ground coat can just be seen through the wet cover coat. Dry and fire for 3 or 4 minutes at 820ºC. A second coat should applied if the ground coat can be seen after firing.

Firing by torch or kiln
Fusing of the enamel is best carried out in a kiln regulated by a temperature controlling simmer state switch.
KFiring kiln

Firing in a kiln

Pyrometers are recommended so that temperatures can be recorded for subsequent firings as enamels will vary in colour if fired at different temperatures. Enamelling temperature is 800ºC and should be reached in 1 1/4 hours. As loss of heat occurs when the door is opened the kiln should be preheated to 850ºC. Supports made from nickel chrome or stainless steel may be required.
Stainless steel supports

Stainless steel supports and fork

A small hot plate kiln stood on heat proof pad is useful for small work.
Small kiln

Small hot plate kiln stood on substitute asbestos pad

Small work pieces up to 125mm (5") in diameter can be fired with a blowpipe. Firing should take place on 7mm (1/4") wire mesh, called panning metal approximately 300mm (12") square, supported by a tripod fire bricks.
firing mesh kiln

Firing on a 7mm steel mesh supported by fire bricks

The heat must be applied from underneath the work piece, ceasing when the enamel becomes molten and smooth or burning out of the enamel at the edges will take place.

Finishing

When the object has been fired and the back has not been enamelled, it will require cleaning on the back. Normal oxides can be removed in a bath of 10% Sulphuric acid, first the enamel has to be protected with wax or it will become frosted. The normal cleaning processes then are undertaken.

Silver Solders and Fluxes.


Silver Soldiers.

A lower melting point is obtained if the soldering alloy contains silver. Oliver articles should be soldered with a solder matching the colour of the standard silver and satisfying hallmark requirements. Cheaper commercial grades are available, often having a yellow colour, but butte suitable for soldering copper or gilding metal. A number of grades, having different melting points, are available in order that several Joints may be incorporated on the same job, previously joints being protected with an application of jeweller's rouge and loam mixed with water.

Grade. Melting point Form Use

Extra easy 680 - 700 Strip/sheet/rod 5th joint/general
Easy 705 - 723 Strip/sheet/rod 4th joint/general
Medium 720 - 765 Strip/sheet/rod 3rd joint/general
Hard 745 - 778 Strip/sheet/rod 2nd joint/general
Enamelling 730 - 800 Strip/sheet/rod 1st joint/enamelling


Fluxes.
Oxidisation has to be prevented in hard soldering by the use of a flux. The most common is a colourless crystalline salt, found in California, known as Borax, a creamy paste being formed when mixed with water in its powder form or rubbing It against a saucer or slate when obtained’s a cone. A number of excellent efficient patent fluxes are available. Application should be by means of a clean brush.
Borax cone

Borax cone for soldering.

Blowpipes and Hearth

In order to perform the action of soldering successfully a hearth is required. A revolving hearth is to be preferred and is obtained free standing or bench mounted, with a motorised blower or double foot bellows supplying the air. (fig 322) A lining of fire bricks should be used, with non-asbestos cubes round their periphery and a 300 mm. (12") square or 7 mm (1/4") iron wire mesh placed on top. On no account should soft soldering be carried out on this hearth or damage to work will result. Non-ferrous metals being stained or holes burnt into them if lead solder ls left on the hearth.

A number of blowpipes are available for use with natural gas, coal gas or bottle gas, the former two being mixed with oxygen supplied by compressed air or foot bellows.

A very adequate supply of air supplied by a motorised blower or foot bellows should be used with natural gas.

The blowpipe should be light to handle allowing easy careful control of the flame size with one hand. Mouth blowpipes are used for fine work.
Mouth blowpipe

Mouth blowpipe for soldering.

Soldering Technique.

The joint should be a good grease and oxide free fit being firmly held in place by soft iron binding wire, cotter pins or stitches made with a graver.

wirebinding

Binding with iron wire for soldering.

cotterpin

Sheet clips and cotter pins for sopport.

stitchspout

Stitching for spout



binding

(fig 224) Binding for soldering.

An adequate coating of flux paste should be applied to the joint area before heating commences. If flux wetting is difficult farm the work with the blowpipe or add a 2% solution of “Teepol” to the paste. The work should then be heated up slowly with the blowpipe held some distance from the work: keeping the flame moving over as wide an area as possible. The revolving hearth should be rotated slowly with one hand and the non-luminous part of the flame played on the work with the blowpipe held in the other hand. Heating Is continued until about dull red, when the flux bubbles, and ls continued until about cherry red when a fluxed solder strip, held in tongs melts on contact with the joint.
fluxstrip

Using flux and strip for soldering.

The solder ls fed into the joint until it is slightly overfilled, remembering that solder flows towards heat and should run along the joint. Solder may also be applied by placing small pieces called paillons along or between the joint before heating commences.
Paillions

Placing paillions for soldering.

The work after soldering should then be allowed to cool slowly or cracking and distortion will occur. Holding devices are then removed and the work cleaned by pickling in acid.

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