An alternative (not used in the 21st century due to safety issues) is to mine asbestos fibers and braid or twist them into a yarn. Non-burning wick. read more
(The cork float may have a different shape than that pictured.) Note: most churches prefer to use a length of standard wick, so vigil lamps can remain burning for long periods of time. Many lay people find these 1/2 inch waxed wicks a bit easier to use, because there is not a need to trim the wick. read more
So to get the best possible results, you need to maintain as little a distance between the oil and the flame as possible. You need a wick that’ll move with the oil level in the jar. You need a floating wick. Floating wicks have been around for a long time and they work by having a metal (often aluminum) foil on top of a cork floater. read more