Glass Discs and Panels

Glass Discs and Panels

John Moncrieff Ltd glass discs and panels. We offer Maxos brand circular sight glass. Maxos is the brand behind all leading level gauges and sight ports:

  • Jerguson (Clarke Reliance)
  • Penberthy
  • Klinger
    Circular Sight Glass

    Circular Sight Glass

  • Bonetti
  • Bunki Boeki
  • Nihon Klingage
  • Yarway
  • Diamond Power

Our range of standard sizes and technical information

Glass Discs and Panels | Custom Manufacture

As well as our standard range, we also produce custom sizes in a variety of materials, to the size you demand. Any flat shape is possible: Obround, Panels, etc and the other techniques.

We are able to offer glass cut to your exact specification, using either hand or waterjet cutting facility.

This allows you to achieve any flat shape you required, in any thickness available with a quality professional finish.

The waterjet can also cut other materials, such a metal, stone, plastic and marble.

We have the facility to be able to toughen or temper glass.

According to the type and thickness of glass, we can offer either heat or chemically toughened options.

This toughening process is generally only available on flat glass, it increases the impact resistance of glass and to create a break pattern compliant to BS Standards.

Sandblasting creates a frosted/opaque finish to your glass.

This is particularly useful when the requirement is to diffuse the light.

Sandblasting can be applied to all types of glass: soda-lime, toughened, ceramic and borosilicate.

It also looks attractive on decorative glass.

Arraised edges to take the sharpness.

Bevelled edges in ground or polished finish.

Holes can be drilled and countersunk or plain.

Very accurate tolerances can be maintained for grinding:

  • circles
  • shapes
  • squares
  • rectangles

on our specialist precision machines.

We have the facility to provide bent and curved glass to an array of industries using annealed, laminated and coloured glass.

It can also be termed slumped glass.

We carry a certain number of moulds, but if you require a custom made unit, we are able to prepare your mould.

Any pattern, design and colour can be reproduced onto a screen and printed using high-temperature ceramic paints or low-temperature polyscreen inks.

Only the customer’s artwork and film are required, after which we can make the screens in-house.

Printed glasses are highly effective when used decoratively and can be applied to soda lime, borosilicate or toughened glasses.

Circular Sight Glass | Glass Types

The glass type you require depends on environmental conditions (temperature, pressure, aggressive media..

The basic types of materials used for the manufacture of sight glasses are:

  • soda-lime glass – widely available, working temperature up to 280 °C,
  • borosilicate glass – particularly suitable for use in aggressive environments (acids, alkalis, water vapor), working temperature up to 350 °C,
  • aluminosilicate glass – working temperature up to 750 °C,
  • glass-ceramics – thermal shock resistant, working temperature up to 750 °C,
  • quartz glass – with a broad spectrum light transmittance (from ultraviolet to infrared), working temperature up to 1200 °C,
  • sapphire products – working temperature up to 2000 °C.

To improve the strength, the machined glass in certain circumstances can subjected to toughening and annealing.

In order to increase the resistance of sight glasses on the aggressiveness of the working environment and in the use of high temperatures and pressures, a mica shield is recommended. Mica disc working as shields are described here. If you need this solution – please contact us. Circular sight glasses are delivered separately or in a set with gaskets.


Ports Gauge Kits are used in high pressure level gauge application. The kits vary according to the Glass Manufacture, but generally the comprise of:

  • High Pressure Port Glass
  • Micas
  • Gaskets

We are able to prepare these kits at a much more competitive rate than the OEM, among the kits we produce are for the following brands:

  • Yarway/Narvik
  • Diamond Power
  • Bonetti
  • Bunkaboeki Kogyo(BBK)

Please contact us for additional information.

Port Gauge Kits for glass discs and panels


If you are working with steam, hot alkaline, or acidic solutions a mica shield is the best way to protect the integrity of your gauge glass. Over time liquids and steam will wear down even the toughest gauge glass causing it to eventually crack, or have what looks like a melted appearance. A mica shield helps to prevent corrosion and extends the lifetime of the gauge glass..

The mica shield that you need depends on the type of process fluid you are working with and your application. Mica shields at the highest quality level, designated by V1, are clear and flat providing the highest level of visibility as well as protection. V1 mica is not obstructed by cracks, air pockets, colors or other factors.

V2 mica shields are slightly colored, and are considered to be navy-grade quality. The most common choice of grade suitable for most applications, whilst being economical in price are V4 mica shields. These have more noticeable discoloration, and may contain some air pockets and a slightly wavy appearance. These mica shields still provide suitable protection from steam and alkaline solutions, but have some reduced visibility.

Please contact us for additional information.