Circular Sight Glass

Product Code: Circular Sight Glass

John Moncrieff — Sight Glass Materials & Selection Guide

Selecting the correct sight glass material is essential for ensuring long-term performance, safety, and clarity under varying environmental conditions such as temperature, pressure, and chemical exposure.

At John Moncrieff Ltd, we offer a comprehensive range of sight glass materials to suit every industrial application — from standard process observation to extreme high-temperature or corrosive environments.

Common Sight Glass Materials

Soda-Lime Glass: Widely available and economical, suitable for general-purpose applications.
Working temperature: up to 280 °C.
Borosilicate Glass: Excellent resistance to acids, alkalis, and water vapour. Ideal for aggressive chemical environments.
Working temperature: up to 350 °C.
Aluminosilicate Glass: High mechanical strength and heat resistance for heavy-duty applications.
Working temperature: up to 750 °C.
Glass-Ceramics: Outstanding thermal shock resistance and stability under temperature fluctuations.
Working temperature: up to 750 °C.
Quartz Glass: Exceptional optical clarity with broad-spectrum light transmission (UV to infrared).
Working temperature: up to 1200 °C.
Sapphire Glass: Extremely hard and durable, suitable for ultra-high temperature and abrasive environments.
Working temperature: up to 2000 °C.

Strength Enhancement

To further increase strength and impact resistance, sight glasses can be toughened or annealed after machining — providing added safety and durability in high-stress applications.

Protection with Mica Shields

For applications involving high pressure, high temperature, or corrosive media, we recommend using a mica shield to protect the glass surface. Mica shields act as a protective barrier, extending the lifespan of the sight glass and maintaining optical clarity even in harsh process conditions.

Circular sight glasses can be supplied individually or as a complete set with gaskets.

For assistance selecting the ideal sight glass material or shield configuration, please contact our expert team.

Please see below links to our Standard Sizes & Technical Information: