Manual of Instruction in Hard Soldering
Contents
- Rowell opens by arguing that mastery of heat is the foundation of civilised progress and practical metalwork. He encourages the reader to study the subject thoroughly, using each piece of knowledge as a stepping stone to further observation and experiment.
- Covers the equipment needed for hard soldering: lamps and gas burners, charcoal blocks, mouth blowpipes and their construction, wash-bottles for cooling, binding wire, and borax. Also lists the chemical reagents — nitric acid, sulphuric acid, bichromate of potash, saltpetre, ammonia, and yellow ochre — whose uses are explained in later chapters.
- Explains how to prepare the three main hard solders: spelter (low brass, used on copper and iron), silver solder (silver, copper, and zinc, giving strength and oxidation resistance), and gold solder (gold alloyed with silver and copper in proportions matched to the carat of the work). Rowell gives specific recipes, melting and casting instructions, and warns against arsenic additions.
- Describes how atmospheric oxygen attacks metals during heating and ruins joints, then explains how fluxes and anti-oxidising pastes intercept that attack by melting over the surface and dissolving any oxide formed. Different protective approaches — borax for welding, various fluxes for brazing — are compared, and the gunsmith bluing and brass ormolu finishes are cited as examples of protective oxidation.
- Analyses the zones of a lamp flame — inner cool gas cone, outer oxidising mantle, and the reducing inner region — and shows how a blowpipe modifies them into distinct oxidising, reducing, and neutral flames. Rowell explains how each flame type is selected for different stages of soldering: oxidising to bring cold metal up to temperature rapidly, reducing to protect surfaces once hot.
- Covers the three modes of heat transfer — conduction, convection/radiation, and reflection — and their practical consequences for the solderer. Includes Regnault's table of specific heats for metals (aluminium through zinc) and discusses how different conductivities and specific heats require the craftsman to adjust flame placement and timing.
- Step-by-step instruction for a beginner using the mouth blowpipe, alcohol lamp, and charcoal: setting up the work table away from strong light, cleaning and fitting joints, applying borax paste, binding pieces with iron wire, applying solder, and managing the flame sequence. Practical exercises include making a ferrule and repairing a spoon, with guidance on common difficulties such as maintaining breath control and avoiding uneven heating.
- Extends the process to more demanding work: repairing a watch case (with advice on plumbago plugs to protect hinge holes), hard soldering with a forge or hearth for large pieces, and hard soldering with heated tongs for lap joints that cannot be held in a flame. Discusses preventing the work from being displaced by heat expansion and the use of binding wire and clamps.
- A practical reference covering a range of workshop problems: preserving thin edges from burning away, making the silversmith's pickle (nitric and sulphuric acid solution) for cleaning, restoring colour to gold with chromic acid, mending steel springs, sweating metals together without solder, retaining work in position with wire and pins, forming joints, and precautions when heating gems or enclosed hollow articles. Also includes warnings about sulphur, lead, and zinc contamination when using a forge.
- Tables of specific gravity and melting points for the principal metals (aluminium, bismuth, copper, gold, iron, lead, nickel, platinum, silver, tin, zinc), with notes on how alloys deviate from the mean melting points of their constituents. Provides the numerical data a solderer needs to choose appropriate temperatures and avoid damaging the parent metal.
- Supplementary notes added in later editions: chemically treated charcoal mats and asbestos/magnesia blocks for supporting work during heating, the use of a steel pointer tip on the mouth blowpipe to guide molten solder, and the technique of investing delicate articles in a paste of whiting and water (or plaster) to hold their shape and distribute heat evenly during soldering in a muffle furnace.
- Practical instructions for brazing steel bicycle frame tubes using spelter or silver solder over a hearth or double gas-jet forge. Covers joint preparation, flux application, wrapping tubes with asbestos cloth to protect from excessive heat, and the sequence of applying spelter at low red heat so it flows fully into the joint.
- Explains how the same principles of cleanliness, flux protection, and controlled heating apply to soft solder (tin-lead alloys), while the tools differ: the soldering copper replaces the blowpipe, and rosin or zinc chloride solution replaces borax. Covers tinning the copper, fluxes for different metals, repairing plated-ware and gun rib lugs, and the caution needed to avoid over-heating thin electroplated surfaces.
- A brief update reviewing improvements in hard-solder alloys since earlier editions, including dentists' zinc-containing gold solders that resist mouth acids, and notes on the evaporation of zinc during fusion. Serves as a condensed supplement to Chapter II for readers needing the latest alloy formulations.