The Difference Between Making a Candle Glass by Pressing and a Bottle by Extrusion

Glass packaging may look simple on the surface, but the manufacturing process behind it plays a major role in how the final product performs. In the candle industry, pressed candle glasses (sometimes referred to as pumped or press-moulded glass) are very different from extruded or blown glass bottles.

Understanding these differences helps candle makers choose the right candle glass or candle vessel for safety, durability, and performance.

How Pressed (Pumped) Candle Glasses Are Made

Pressed glass is the most common method used to manufacture candle glasses and candle jars.

The Pressing Process

In pressed glass production, molten glass is dropped into a mould. A metal plunger is then pressed (or pumped) into the glass, forcing it into the shape of the mould. The glass is then cooled and annealed to strengthen it.

This process creates thick, uniform walls and a solid base, features that are essential for candle vessels.

Why Pressed Glass Is Ideal for Candle Jars

Pressed candle glasses are designed to withstand heat. Key benefits include:

• Thick glass walls for heat resistance

• Strong, heavy bases for stability

• Consistent wall thickness

• Reduced risk of cracking during burning

Because of these qualities, pressed glass is the preferred method for producing safe and reliable candle vessels.

How Extruded (Blown) Glass Bottles Are Made

Extruded or blown glass is commonly used for bottles and containers designed to hold liquids, such as perfumes, oils, and beverages.

The Extrusion / Blowing Process

In this method, molten glass is formed into a hollow shape using air pressure. The glass is blown or extruded into a mould, creating thinner walls and a lighter structure. This process allows for more complex shapes and narrow necks.

Why Extruded Glass Is Better for Bottles

Extruded glass bottles offer:

• Lightweight construction

• Thin, even walls

• Narrow openings and necks

• Greater design flexibility

These qualities make them perfect for liquid products but less suitable for candles.

Key Differences Between Pressed Candle Glasses and Extruded Bottles

Glass Thickness

Pressed candle glasses have thicker walls and bases, while extruded bottles are thinner and lighter.

Heat Resistance

Pressed glass candle vessels are designed to handle sustained heat from burning candles. Extruded bottles are not intended for prolonged heat exposure.

Structural Strength

Candle jars require stability and durability. Pressed glass provides strength, whereas extruded bottles focus on shape and weight reduction.

Intended Use

• Pressed glass: Candle jars, candle vessels, tealight holders

• Extruded glass: Bottles for liquids, perfumes, oils, and beverages

Why Candle Makers Should Avoid Using Bottle Glass for Candles

Using an extruded bottle as a candle vessel can pose safety risks. Thin glass walls may overheat, crack, or shatter under candle heat. Pressed candle glasses are specifically engineered to handle thermal stress, making them the safer and more reliable option.

For this reason, reputable candle manufacturers always choose pressed candle jars rather than repurposed bottles.

 

Sustainability Considerations

Both pressed and extruded glass are recyclable, but pressed candle glasses often have a longer life cycle. Consumers frequently reuse candle jars for storage or refills, extending their usefulness beyond the original product.

The difference between making a candle glass by pressing and a bottle by extrusion lies in purpose and performance. Pressed glass is designed for heat resistance, durability, and safety, making it ideal for candle jars and candle vessels. Extruded glass, while excellent for bottles, is not suitable for candle use.

Choosing the correct glass manufacturing method ensures safer candles, better burn performance, and a higher-quality product overall.