The solder pictured here was made by the Rawlplug company, prior to decimalisation and probably dates from the 1950s or early 1960s. The small quantity of solder wire that is wrapped around each cardboard holder suggests that the items were sold for home use. A professional electrician or manufacturer would be expected to have a much larger container.
The soft metal from which the wire is made has a low melting point and has a high conductivity and is designed to be melted on to metal surfaces to permanently join them together. In the home these would most often be electrical wires and terminals. The fact that this is ‘cored’ solder means that the wire is hollow and inside there is a flux chemical to aid the flow of the molten metal. At the time this solder was sold, electrical products were easier to mend than in these days of miniature electronics.
The cardboard holders do not state the type of metal from which the solder is made, simply that it is non acid. Alloys of 60% tin and 40% lead were common in the past and these are likely to be the metals used in the vintage solder depicted here. Although still used, lead is being replaced by bismuth and other metals.
To melt the solder and apply it to the surfaces to be joined, a soldering iron is used. This is an electrical appliance, with an insulated handle, a shaft and a heated tip, which is used to apply the solder. A typical soldering iron is illustrated below.
The name ‘Rawlplug’ is rightly associated with fixings. The first rawlplug was invented by John Joseph Rawlings, who had been commissioned in 1910 to renovate The British Museum, during which task he produced a wall plug made of jute soaked in a mixture of animal blood and glue. The Rawlplug brand was registered in 1912. Many of us will have brown fibre rawlplugs at home and/or later plastic or metal fixings made by the company. They no longer make solder.