A tealight, or nightlight, is a candle used in tea or food warmers or (because they last for many hours) as a night light. It is different from a regular candle in that it is encased in a thin metal cover and liquefies completely while lit. Tealights are often used to heat fondue and as food warmers. They are also suitable for accent lighting and for heating scented oil. In tealights the wick is tethered to a piece of metal to stop it from floating to the top of the molten wax and burning before the wax does. Generally, tea lights give off very poor light unless grouped together with many other tea lights; they were designed to be a long-lasting comfort light rather than a working or reading light. Tealights may be distinguished from Nightlights by the duration of burning; a tealight usually burns for 4 to 5 hours but a nightlight, which is larger, is intended to burn for a whole night (about 8 to 10 hours).
As candles have become popular again, tea-light candles have been protected under several patented designs. In some cases, the standard tea light metal cup has been replaced with a clear plastic cup. However, the metal cups are still offered by many candle makers. The clear cup allows more light to escape the holder, and even offers a “stained glass” look when multiple colors are used. In the early 2000s, a new shape of cup was patented to encourage more even burning and complete liquifaction of the wax. The new cup shape slopes inward toward the wick, forcing the wax pool toward the wick. This technology change has worked to increase burn time and in some cases scent throw. These candles are also available in decorative pieces.
Tealights are increasingly implicated as the cause of domestic fires and a common form of misuse is the placing of spent matches or other debris inside the tea-light during use. This can lead to dangerous overheating.
The overheating leads to the wax reaching its “fire point” and igniting. As the wax is consumed the excessive heat is tranferred to the metal of the holder. The base reaches temperatures exceeding 300 Celsius. This is sufficient to melt through plastic and if the tealight has been placed unprotected on a television or other cabinet-style plastic items it will melt the plastic. The hot tealight falls through the hole created and, if the plastic is not fire resistant, the flame ignites the edge of the hole as it passes. This has led to many uncontrolled fires and some deaths.
It is not an issue only of misuse: some tealights are of poor design or quality, some are subject to poor quality control in manufacture.
There is a substantial amount of research on this subject in the UK. The first paper and formal identification of the problem was presented in October 1999 by David Townsend of the London Fire Brigade, United Kingdom. This led to further study in November 2000 by the Consumers Association on behalf of the Department of Trade and Industry
Tealights can come in many different shapes and sizes, as well as burn times and scents. Some tealights can be used together to create a certain atmosphere.
Tealights are especially popular for use with candle holders. From small pockets of stone, river stone, cast stone, glass, metal, ceramic and other materials to larger, more elaborate tea light lamps, holders come in a wide range of styles, colors, and shapes. Holders have an appropriately sized cup to use a tealight candle, either scented or unscented. Discount stores, gift stores, and home decor stores often carry an array of holders for these small candles.