It's probably something you urge every customer to do - but why do we have to trim our wicks before lighting?
The main reason to trim your wick is to prevent sooting.
Keeping your wick trimmed reduces the amount of melted wax (i.e. fuel) that the candle produces. Sooting can occur when there's too much wax melted - and therefore too much "fuel" for the wick to keep up with.
All this being said - it's really easy to forget to trim your wick. Especially if you don't know the ins-and-outs of candle making.
This is why at Vuur, we complete robust testing to ensure that our candles can safely burn, even without being trimmed.