The Finnish New Year's Eve tradition that uses molten tin to predict the coming year is tin casting. A small piece of metal is melted and poured into cold water, where it solidifies into an irregular shape. People then interpret the shape, often by examining its shadow in candlelight.
Traditional interpretations connect forms with possible events or themes. A ship might suggest travel, while a ring can be associated with marriage or commitment. These readings are symbolic rather than scientific forecasts, and families may invent their own interpretations as part of the fun.
The practice was historically associated with small horseshoe-shaped pieces of tin sold for New Year celebrations. Concerns about lead and other metals have led to safer alternatives in some places, including wax or special metal-free products. Finnish New Year customs also include fireworks, parties and watching televised celebrations.