In the 1950s there was a switch in fuel choice from naphtha to butane, as butane allows for a controllable flame and has less odor. This also led to the use of piezoelectric spark, which replaced the need for a flint wheel in some lighters and was used in many Ronson lighters. In 1965 Société Bic launched its first lighter design and in 1998 introduced the child-safety feature, a metal shield over the flint wheel, seen on all modern Bics. Bic lighters are made to be cheap and disposable.
Naphtha based lighters employ a saturated cloth wick and fiber packing to absorb the fluid and prevent it from leaking. They employ an enclosed top to prevent the volatile liquid from evaporating, and to conveniently extinguish the flame. Butane lighters have a valved orifice that meters the butane gas as it escapes.
A spark is created by striking metal against a flint, or by pressing a button that compresses a piezoelectric crystal, generating an electric arc. In naphtha lighters, the liquid is sufficiently volatile, and flammable vapor is present as soon as the top of the lighter is opened. Butane lighters combine the striking action with the opening of the valve to release gas. The spark ignites the flammable gas causing a flame to come out of the lighter which continues until either the top is closed (naphtha type), or the valve is released (butane type).
A metal enclosure with air holes generally surrounds the flame, and is designed to allow mixing of fuel and air while making the lighter less sensitive to wind. The high energy jet in butane lighters allows mixing to be accomplished by using Bernoulli's principle, so that the air hole(s) in this type tend to be much smaller and farther from the flame.