Why Do Some Glass Candle Jars Have Seam Lines?

Seam lines on glass candle jars are a normal result of the manufacturing process, not necessarily a defect. They are formed during molding and are common in mass-produced glass containers.

How Are Seam Lines Formed?

Most glass candle jars are made by:

• Press molding (pressed glass), or

• Blow molding (machine-blown glass)

Both methods use metal molds that close together to shape molten glass.

When:

1. Molten glass is poured into the mold

2. The mold closes and shapes the glass

3. The glass cools and solidifies

The joints where the mold pieces meet leave a thin line on the surface.