Lit Candle to Milk or Salt

A candle on display is lit, for some part of another routine, or you can light it for this specific effect.

It is covered with a small cap to extinguish the flame. When the cap is removed, the flaming candle tip has vanished, and the candle has transformed into a clear cylinder of milk, which you can pour out.

Or if you prefer, the cylinder could be full of fine salt or sugar which pours out in an endless stream. It could even be a rolled up white silk!