We had to retain and collect the candle wax. Birthday candles were instantly out of the question, as their long, thin design meant that the wax would not be able to solidify in the vessel supporting the candle. Instead, it meant that the wax would solidify on the structure of the candle itself. Therefore, we would be unable to reuse the wax fully if the wick burns out.
A solution was found when we used short, thick wax candles. Their short height meant that the liquefied wax had to travel a shorter distance before it is collected in the vessel supporting the candle, and would lose less heat to the surroundings. Subsequently, the wax would be collected and solidified into any shape we desire – it is dependent on the shape of the vessel.