Density. At about 19.3 grams per cubic centimetre it is roughly 70 per cent denser than lead and comparable to gold, so a required mass occupies far less space. That is decisive wherever volume is fixed - balance weights in rotating assemblies, aircraft trim, and mass added inside a boring bar to suppress chatter.

Tungsten powder liquid-phase sintered with nickel and iron or nickel and copper, typically 90 to 97 per cent tungsten. It retains most of the density while being far tougher and genuinely machinable, unlike pure tungsten. Most commercial counterweight, ballast and shielding parts are made from it rather than from pure metal.

It can, and it is specified where lead is unacceptable on toxicity grounds or where space is restricted, since a thinner tungsten section gives the same attenuation. The obstacle is cost, which is many times that of lead, so it is used for collimators, syringe shields, portable equipment and similar rather than for room linings.

It is brittle at and near room temperature, so it chips and cracks rather than cutting, and it is extremely hard and abrasive. Most pure tungsten parts are produced by powder metallurgy to near-final shape and finished by grinding or EDM. Where machining is genuinely needed, tungsten heavy alloy is used instead.

Pure tungsten and, more usually now, grades with oxide additions - lanthanated, ceriated and the older thoriated type - which improve arc starting, arc stability and current-carrying capacity. Thoriated electrodes are mildly radioactive and are being displaced by lanthanated grades for grinding-dust exposure reasons.

Yes. It oxidises rapidly in air once hot and the oxide does not protect the surface, so the metal is progressively consumed. High-temperature use therefore takes place in vacuum, hydrogen or inert gas - which is why tungsten appears inside furnaces, lamps and vacuum equipment rather than in open-air hot service.

Rod, wire, thin sheet and foil, plus sintered blanks, electrodes, boats and targets. Section sizes are limited compared with common metals because of how the material is produced, and heavy alloy is available in larger and more machinable forms, which is why design usually starts from what is stocked.