Silversmithing and Jewellery

Silversmithing and jewellery

http://www.ba-education.com/for/hobbies/silversmithing.html[7/15/2014 7:45:35 PM]

SILVERSMITHING


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, asindeed 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 ofsilver, copper and gilding metal are often used as these can then be silverplated if required. Brass is usedwhen its colour is important, but when it is annealed it is too hard for most hollowing processes. Pewter and itsmore modern counterpart Britannia metal, which contains no lead, is is more expensive than copper andpresents 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) forjewellery 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 forsilversmithing.

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

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

Hammers and Mallets

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

Raising 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").

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

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



Repoussé punches

ProcessesHollowing 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 awooden block or Sandbag with a round ended bossing mallet or Blocking hammer.

Hollowing

When the disc has been cut the burrs on the edges are removed with a smooth file or paper, thus preventinginjury to hands and also preventing the small burrs from breaking off, entering the mallet face and damagingthe surface of the disc when stuck. The disc should then be softened by a process known as annealing, whichby raising the temperature of the metal, the deformed grains recrystallise into new undistorted grains, thusrestoring it to a soft and ductile structure. This is carried out on a revolving hearth with a blowpipe. The disc isrevolved 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 theearly stages of forming quenching in water can be permitted. The oxide and impurities are then removed bypickling in the acid bath. The disc is then removed with tongs or basket from the acid and washed thoroughlyunder running water, cleaned with pumice powder and brush, then dried in sawdust. All work must be cleanedafter each heating or the oxide and the impurities on the surface will be hammered into the surface of the metaland 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 shouldbe marked with a pencil line from the centre to the outside and a number of concentric circles drawn with apencil compass to act as a starting radius line and guide lines when 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 orblocking hammer about 10mm (3/8") from the near edge. The disc is then turned until a full circle has beenachieved and then the next circle is commenced until the middle has been reached. If crinkles or buckles areformed at the edges these should be hammered out as they appear. When the work becomes work-hardenedthrough repeated hammering or the centre has been reached the metal must again be annealed or cracks willappear. This process is repeated until the required shape is achieved and is the preliminary preceding processto raising.

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



Doming

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

Sinking

To commence the disc is marked out to the width of the desired rim and the depth of recess. Annealing thentakes place as in hollowing. Next the sinking block is placed in a vice and the horizontally held metal sunk intothe shape on the wood with a Bossing mallet or Blocking hammer whilst being held in place and rotated withthe other hand. If a circular article is being sunk two pins may be placed in the wood block to help guide the flatsurface 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 hasbeen 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 tallershapes, without a steam, by striking the metal on its outside instead of its inside. The tools used are the raisingstake, 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 modernworkshops lathes for spinning (fig 439) have superseded raising for repetitive articles which are then finishedby hand. Work which is usually a disc for a circular shaped article is first annealed and cleaned andsubsequently annealed and cleaned after each raising or course. The disc is then slightly hollowed and thenmarked out with concentric pencil circles. The hollowed disc is then placed against the stake so that the end ofthe stake is at the back of the line at which you wish to commence. The metal is now struck with the raisinghammer making sure that the toe of the hammer gets well down (fig 260).

Raising

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

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 eachblow the job is rotated to its next position and the iron struck again until the desired shape is achieved.

Snarling

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



Caulking

Planishing This is the finishing process which trues the shape of the article, no matter how it was formed, and removes allthe previous working marks from the surface. The tools required are a planishing hammer with one domed andone 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 drawn5mm (3/16") apart on the surface with a pencil compass to act as guide lines. A stake with a slightly smallerradius than the article being planished should than be got ready and the article placed on it. The planishinghammer should then be paced on the article, thus holding it in position on stake. To start planishing the freehand firmly holds the article and will after each tap of the hammer rotate the article. The hammer is then liftedand the surface of the article is lightly struck with a wiping motion, which will produce a clear ringing note, thusindicating a true contact with the stake. The hammer must rise and fall constantly over the same spot on thestake, whilst the work is rotated, and then small or large facets will be produced depending on the weight of thetap. Starting from the centre, each circle of the guide lines should be planished in turn, each facet being ofuniform size should overlap the previous one and the one on the preceding row.



Planishing

When the whole surface has been completed it may be necessary to planished it two or three times to removeall 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 processof planishing the metal is hardened, stretched and thinned. Its prime object is to smooth and true the article, notto 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 andseaming 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 areprepared by filing or scraping to an angle of 45ºC and the sides are then brought up, forming nice sharpcorners.



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 thesame shape a sheet is made to fit the open side of the box. Before the sheet is fitted, wired, fluxed andsoldered, the previously soldered joints should have an application of jewellers rouge and loan to prevent themrunning.

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

Box lid cutting

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

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 seriesof shaped holes in a draw plate held in a vice or on a draw bench.



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



Hing Tubes

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

Twisting

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



Bending

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

Spout

Settings A many semi precious stones can be purchased for a few new pence, a number of simple settings are shownhere, the most simple being the bezel, which consists of a thin strip of metal fitted closely to the stone to beheld 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 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 orpurchased ready-made.

Jewellers Findings



Decoration

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

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

Repoussé punches

To commence, the design is transferred from your previously prepared drawing to the work by means of Keil orcarbon 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 tappedradially it moves towards the worker, making a smooth indented line.



Chasing

To sharpen up the design the work can then be reversed and the face chased with tracing punches. Texturingcan 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 thehand (fig 275). The graver is shaped and sharpened so that it tends to raise the handle when it is run parallelover the surface of the metal. Sharpening should be commenced on an Indian stone and finished on 000 blueblack emery paper held on a flat surface.

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 slightmovement of the graver, away from the worker.

Engraving

Etching Etching is a process by which the surface of a metal may be decorated by the controlled eating away by acid ofareas 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” orpolythene container being used for an etching bath although a wall of wax round a small area to be etched issufficient. The work should be laid sloping face down and prevented from a touching the bottom of the bath bymeans a string cradle in order that the sediment falls away.

String cradle

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

Gold (18 k. or lower)

Hydrochloric acid 8 parts



Nitric acid 4 partsIron perchloride 1 part

Water 40 parts

Silver, iron and steel

Nitric acid 1 partWater 3 parts

Aluminium

Iron Perchloride 1 partWater 1 part

Copper, gilding metal, brass

Iron perchloride 3 partsWater 1 part

Metal Preparation The surface on which the acid resist is to be attached must be thoroughly cleaned of all grease and oxides. Afine 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 suitablefor a particular job.

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

Wax removal by etching needle



After etching the wax is then removed by heating the work and wiping off, or dissolved off in benzine oracetone. 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 containeither 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 frontedges and back. The edges will require two coats as the varnish tends to creep away from them. The varnishtakes several minutes to dry and, if placed in the acid wet, under biting will occur. Several methods ofdecoration can be achieved with varnish. The first is by means of dripping and trailing a treacle consistencyvarnish over the surface to be decorated. The second is by painting round the lines of a previously transferreddesign. The third method in which the design is first painted on with a slow-drying substance known as liftground made from equal parts treacle, gum Arabic and “Isinglass” in a small amount of water.

Lift ground paint

Then all this is covered with the 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 partpainted with lift ground will then come away leaving the design ready.



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 partsbeeswax, 2 parts asphaltum and 1 part pitch (Swedish or Burgundy). If made, the wax and pitch are melted ina saucepan, stirred and the asphaltum added. After 20 minutes the is poured into warm water and rolled intothe appropriate sized balls. In use the ground is placed in a piece of fine cloth and the ends brought up andtied to form a handle thereby forming a dabber.

Dabber

The previously cleaned work is then warmed, the dabber rubbed on the surface and rocked in a, circularmotion. The work is again heated until a glazed even unburned deposit is formed. The edges and back arethen 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, orbetter still red Keil paper, is placed between the two surfaces and the design transferred by using a pencilwhich will leave a fine line.



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 hardnessand brilliance of the enamels. The colours are obtained by adding varying proportions of metallic oxides andopacity 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 butdue to their low melting point few colours are available.

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

The enamel is produced by smelting the constituents in a fireclay crucible at 1150ºC to 1250ºC and pouring itout 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

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

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 30mash.

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 zincwill 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 mayoccur.

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 scaleby this action. The job is then placed on a clean surface and any remaining scale is removed with pumicepower and then washed. For high class work the metal should be pickled to a clean bright finish by immersingin 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 beprevented.

Ferrous To remove the oil from the surface of the steel it can be wiped with a paraffin rag, scrubbed with pumicepowder, rinsed in water and dried with a clean cloth. A better method of degreasing is to anneal the steel at700 - 75ºC for 3 to 4 minutes, then pickled for 20 minutes in a 10% hydrochloric acid solution until it has aclean, light grey, etched surface. Washing in hot water is followed by neutralising the acid remaining on thesurface by washing in a 1% solution of sodium carbonate. Finally wash thoroughly in hot water and dry, beingmost 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 depositwhen heated. To prepare, first take 14 grams (1/2oz) of gum tragacanth and mix to a creamy paste withmethylated 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 effectand decoration required on the end product. The following methods are intended as an introduction to thesetechniques.



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

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 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 ahole, 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 todrain from one corner. The ground coat is usually supplied in a liquid form and can be thinned with water. Thisis 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 justbe seen through the wet cover coat. Dry and fire for 3 or 4 minutes at 820ºC. A second coat should applied ifthe 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.

Firing in a kiln

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

Stainless steel supports and fork

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



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 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 andsmooth 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 waxor 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 asolder matching the colour of the standard silver and satisfying hallmark requirements. Cheaper commercialgrades are available, often having a yellow colour, but butte suitable for soldering copper or gilding metal. Anumber of grades, having different melting points, are available in order that several Joints may be incorporatedon the same job, previously joints being protected with an application of jeweller's rouge and loam mixed withwater.

Grade. Melting point Form Use

Extra easy 680 - 700 Strip/sheet/rod 5th joint/generalEasy 705 - 723 Strip/sheet/rod 4th joint/general

Medium 720 - 765 Strip/sheet/rod 3rd joint/generalHard 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 colourlesscrystalline salt, found in California, known as Borax, a creamy paste being formed when mixed with water in itspowder form or rubbing It against a saucer or slate when obtained’s a cone. A number of excellent efficientpatent fluxes are available. Application should be by means of a clean brush.

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 bepreferred and is obtained free standing or bench mounted, with a motorised blower or double foot bellowssupplying the air. (fig 322) A lining of fire bricks should be used, with non-asbestos cubes round their peripheryand a 300 mm. (12") square or 7 mm (1/4") iron wire mesh placed on top. On no account should soft solderingbe carried out on this hearth or damage to work will result. Non-ferrous metals being stained or holes burnt intothem 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 beingmixed 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. Mouthblowpipes are used for fine work.

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, cotterpins or stitches made with a graver.

Binding with iron wire for soldering.



Sheet clips and cotter pins for sopport.

Stitching for spout

(fig 224) Binding for soldering.

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



Using flux and strip for soldering.

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

Placing paillions for soldering.

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

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