Gold nibs are not made of fine gold but of alloys with silver and copper components, since pure gold would be much too soft and too little elastic. With 18-carat gold the gold content is just over half, with 14-carat only about 38 per cent. In France previously predominantly 18-carat nibs were sold; meanwhile 14-carat nibs are used there; only Solitaire models still have 18-carat nibs. Allergy sufferers, for skin tolerance reasons, often reach for 18-carat or special alloys like gold-titanium; problematic is only the low-alloy 333 gold. Pure gold is very corrosion-resistant and does not tarnish under normal conditions. For authenticity testing of precious metals, hallmarks and acid tests help.