The chaste of the candle can be due to the quality of the wick or wax, which in most cases we do not find out from the point of view, but it is necessary to look at the composition or ask the manufacturer.
If the wick is made of man-made fibers instead of cotton, there is a high probability that the wick will chad. Unfortunately, we don’t recognize this at first sight.
Another factor is poor quality paraffin.
A poor-quality candle can be recognized by e.g. the hardness of the paraffin, which we find by gently tinging the fingernail from underneath the candle. The harder the material, the better it is. Conversely, the softer (the nail sinks easily and quickly), the more likely a poor-quality product is.
Furthermore, if the candle is not perfumed and there is an unpleasant smell when smelling, e.g. kerosene. It is also a sign that poor quality raw material has been used for production.
Another feature, which does not always mean that it is a poor quality product, is candles, which are dyed in a way of soaking in colored varnishes. The candle is not all colored and white paraffin burns under the varnish. It often happens that by diffusion into colored varnishes, the manufacturer tries to cover up the deficiencies of the underlying material (poor-quality paraffin).
And the last reason may be too long a wick that we forget to trim. Before each use, trim the wick to a length of about 0.5-1 cm.
If we leave the wick longer, it will begin to suck out more paraffin, creating a larger flame that can begin to sing.
If the wick is longer again during burning, it is necessary to extinguish and trim the candle.