Springs

spring for loaded-to-open hinge

Spring hinges usually use wound torsion springs like these. They can be made from steel or stainless steel, and can be plated.

spring for loaded-to-close hinge

The springs for opening and closing differ mainly in the legs. The bend in the closing spring legs allows them to poke through to the back side of the hinge to press the leaves closed.

See our explanation of spring loaded hinges.