A wiped joint is a form of soldered joint used to join

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

pipework.

Process

The defining characteristic of a wiped joint is that the soldering process involves mechanically working or 'wiping' the joint. As well as heating

solder Solder (; North American English, NA: ) is a fusible alloy, fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces aft ...

and applying it to the joint, the solder is shaped into place manually, wiping it with a non-metallic tool to form a smooth-surfaced outer shape. This relies on the use of a

tin Tin is a chemical element; it has symbol Sn () and atomic number 50. A silvery-colored metal, tin is soft enough to be cut with little force, and a bar of tin can be bent by hand with little effort. When bent, a bar of tin makes a sound, the ...

with a wide eutectic range. This is an

alloy An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...

composition that when heated and melted has a large range where it is neither fully solid nor fully liquid, but is an

equilibrium Equilibrium may refer to: Film and television * ''Equilibrium'' (film), a 2002 science fiction film * '' The Story of Three Loves'', also known as ''Equilibrium'', a 1953 romantic anthology film * "Equilibrium" (''seaQuest 2032'') * ''Equilibr ...

mixture of both solid and liquid simultaneously. The resultant 'pasty' texture and mechanical fluidity allows the joint to be wiped to shape. The solder grade used for leadworking is plumber's solder (80% lead / 20% tin). Although this is thought of as a high melting point solder amongst lead-tin solders, the

solidus Solidus (Latin for "solid") may refer to: * Solidus (coin) The ''solidus'' (Latin 'solid'; : ''solidi'') or ''nomisma'' () was a highly pure gold coin issued in the Later Roman Empire and Byzantine Empire. It was introduced in the early ...

is relatively constant for all of these solders and it is the

liquidus While chemically pure materials have a single melting point, chemical mixtures often partially melt at the temperature known as the solidus (''T''S or ''T''sol), and fully melt at the higher liquidus temperature (''T''L or ''T''liq). The solidus ...

which climbs from the

eutectic point A eutectic system or eutectic mixture ( ) is a type of a homogeneous mixture that has a melting point lower than those of the constituents. The lowest possible melting point over all of the mixing ratios of the constituents is called the ''eute ...

at Sn 63% / Pb 37%.

Technique

For pipework, the two parts are first formed to shape so as to fit closely. As lead is a

ductile Ductility refers to the ability of a material to sustain significant plastic deformation before fracture. Plastic deformation is the permanent distortion of a material under applied stress, as opposed to elastic deformation, which is reversi ...

metal, this was easily done by hand using a variety of

mallet A mallet is a tool used for imparting force on another object, often made of rubber or sometimes wood, that is smaller than a maul or beetle, and usually has a relatively large head. General overview The term is descriptive of the ...

s and shaped sticks. Wooden cones could also be used to stretch the diameter of one pipe so that another of nominally the same size could now fit within it. The metal was then cleaned by scraping off the surface, then protecting it with a

flux Flux describes any effect that appears to pass or travel (whether it actually moves or not) through a surface or substance. Flux is a concept in applied mathematics and vector calculus which has many applications in physics. For transport phe ...

tallow Tallow is a rendered form of beef or mutton suet, primarily made up of triglycerides. In industry, tallow is not strictly defined as beef or mutton suet. In this context, tallow is animal fat that conforms to certain technical criteria, inc ...

. Areas that should not receive any lead were painted with ''plumbers soil'' which was a mixture of

lampblack Carbon black (with subtypes acetylene black, channel black, furnace black, lamp black and thermal black) is a material produced by the incomplete combustion of coal tar, vegetable matter, or petroleum products, including fuel oil, fluid catalyt ...

and glue; or flour, salt, sugar and water

The lead would not stick to it, and the plumbers soil would be washed off later. Heat was applied with a

blowtorch A blowtorch, also referred to as a blowlamp, is an ambient air fuel-burning tool used for applying flame and heat to various applications, usually in metalworking, but occasionally for foods like crème brûlée. Description Early blowtorches ...

and when the joint was hot, the end of a bar of solder was applied and melted onto the joint. The molten solder gives a 'pasty' behaviour, owing to its eutectic properties and can be worked for some time before it hardens. Shaping was done with either a '

moleskin Moleskin is a heavy cotton fabric, woven and then shorn to create a short, soft pile on one side. The feel and appearance of its nap is suede-like, less plush than velour and more like felt or chamois. The word is also used for clothing made fr ...

', a heat-resistant pad of cotton cloth, covered with tallow, or else a wooden stick, also greased with tallow.

Applications

Plumbing

Wiped joints were used for centuries to install water

plumbing Plumbing is any system that conveys fluids for a wide range of applications. Plumbing uses piping, pipes, valves, piping and plumbing fitting, plumbing fixtures, Storage tank, tanks, and other apparatuses to convey fluids. HVAC, Heating and co ...

and similar joints can be seen in Roman plumbing. As the wiping technique allowed a great deal of on-site flexibility for the style and dimensions of the work produced, this meant that plumbers needed few parts other than pipe, lead sheet and solder. Large and complex joints could all be made by the artisan's skill alone. With the development of copper plumbing, many different types and sizes of factory-made plumbing fitting were needed, which would be assembled on site rather than fabricated from raw materials. In the later years of lead plumbing, it was recognised that the health effects of lead piping were a problem for drinking water, especially in

soft water Hard water is water that has a high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone, chalk or gypsum, which are largely made up of calcium and magnesium carbonates, ...

areas. Tin-lined lead pipes were used, soldered over a thin brass joint liner. These needed care when wiping the joint, in order to not overheat them and melt the tin layer. Copper to lead joints may be made by wiping the lead onto the copper pipe, as for a lead-lead joint. However the Pb₈₀Sn₂₀ solder used for wiping is poorly

wetting Wetting is the ability of a liquid to displace gas to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. These interactions occur in the presence of either a gaseous phase or ...

onto copper, and so that must be

tinned Tinning is the process of thinly coating sheets of wrought iron or steel with tin, and the resulting product is known as tinplate. The term is also widely used for the different process of coating a metal with solder before soldering. It is most ...

first, using a more tin-rich solder and an active flux.

Underground cables

Lead-sheathed cables were also used for

telephone cable A telephone line or telephone circuit (or just line or circuit industrywide) is a single-user circuit on a telephone communication system. It is designed to reproduce speech of a quality that is understandable. It is the physical wire or oth ...

s, as the lead outer sheath lasted well buried in wet ground. Jointing such cables could also require wiped lead joints. A typical such joint would involve a joint or tee junction between cables, with the copper pairs inside joined by fine soldering and insulating, then the overall joint wrapped in lead sheet and soldered. Such jointing continued until the 1960s and the availability of

polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bott ...

sheathed cables. Wiped joints continue to be made for as long as there are lead pipes in service. Although lead pipework is now rare, for health reasons, wiping a joint remains the usual way of joining it. Commonly though a joint is to be made by shortening the old lead and installing new copper or plastic piping beyond the joint. These joints are usually made today with a proprietary mechanical joint, sealing onto the soft lead by some mechanical compression ring.

Car bodywork

An older technique for body filler on car bodywork, before the plastic age, was the use of

body solder Body solder is a type of solder used to smooth the surface of automobile bodies before painting. It has been largely supplanted by polyester body fillers, such as Bondo, and others, but many purists and auto customizers continue to use body sol ...

. This was a lead-based wiping technique to fill gaps and low spots in steel bodywork, by applying solder with a similar wiping technique and a wooden paddle. The solder used was of even lower tin content, around 10%.

References

{{Reflist, refs= {{Cite book , title=Solder , series= Spons' Workshop Receipts , publisher= Spon , year=1921 , volume=IV – Rain Water to Wire Ropes , pages=188–192 , ref={{harvid, Spon, IV, 1921 {{Cite book , title=Tinning and Wiping , chapter=4: Bending, Jointing and Fixing Pipes , work=The Practical Plumber and Sanitary Engineer , publisher=Odhams Press , year=1946 , editor-first=W.J. , editor-last=Woolgar , pages=92–99 , ref={{harvid, Practical Plumber, 1946 Soldering Lead