How are scented candles made?

The aroma from a lighted scented candle is released through the evaporation of the fragrance from the hot wax pool and from the solid candle itself. Like unscented candles, properly-formulated scented candles will primarily produce water vapor and carbon dioxide when burned

Explanation:

alchemy hadn't scientific methods of study, appeal to mysticism and fantasy, the knowledge of chemistry and physics were modest at that time.

alchemy was - but as new rules were discovered it either changed into chemistry or it became "unscientific".