There are two main categories of period window glass London Crown Glass can supply and they are designed for different applications.

Genuine Handblown Cylinder glass (e.g. German Cylinder Blown Sheet Type NR). This is used for matching existing original Cylinder blown or Crown glass. It is glazed where existing original glass is broken or where replacement windows are required to match existing sashes in a period building. Wherever an authentic appearance is important, handblown Cylinder glass is the preferred choice.

As a genuine handblown glass, each sheet varies a little from the next. The attraction lies in the small blowing imperfections - a few small bubbles (seeds) or a trace of a ream (fold marks or a wave in the glass) found in this style of glass.

Looking through the glass, the view changes as the eye moves. From outside the reflection gently distorts trees, buildings and the surrounding landscape.

The effect which is entirely authentic is derived from the method of manufacture.

The glass is handblown into an elongated balloon. The ends are cut off to form a cylinder, which is then allowed to cool. The cylinder is split lengthways, reheated and then flattened in an oven.

Cylinder glass marked NR (no ream) is the most suitable for window sashes of the late 17th century up to early twentieth century.

Cylinder glass marked LR (low ream) is generally reserved for 16th century or earlier windows in lower grade housing or stables and for leaded lights. This is because the glass has a more heavily marked surface reflecting an earlier style and a lower grade of glass.

We supply the following Cylinder glasses:

1. 1.Vauxhall Glass
   

2. 2.Cylinder Blown Type NR
   

3. 3.Baltic Type LR
   

Because Crown glass is no longer made, we have produced a variant of Cylinder Blown glass called "Vauxhall Glass". This is similar to Cylinder Blown Sheet Type NR but during the final process, the glass is slightly curved to give the bulging appearance of Crown glass.

Period Style window glass. This is a lower cost alternative for complete glazing of windows or a facade where no original glass remains and the fine quality of a handblown glass is not required.

This glass is designed to re-create the gently wavy appearance of Crown and Cylinder glass.

From inside the glass appears without the small imperfections found in handblown glass. However because of the appealing appearance, it is used in place of standard window glass.

Ordinary window glass, which sadly is still sometimes specified for period buildings, is usually Float glass or Horticulture Sheet.

Float glass gives a bland mirror-like appearance when glazed in period window sashes. Horticultural Sheet additionally shows a machine wave spreading across the pane of glass, but only in one direction, giving an unattractive effect. Both Float glass (first used in 1959) and Horticultural Sheet (first used in 1919) spoil the appearance of a period building.

Victorian Sheet is manufactured by a Drawn Sheet process and can be used as one leaf of a sealed double glazing unit.

Victorian Sheet period style glass is generally glazed where no existing mouthblown original glass remains as it does not have the small flaws and imperfections which make Cylinder Blown Sheet glass so appealing, although it gives a similar wavy impression.

It has an attractive exterior appearance and gives a cost effective appearance compared to the use of standard Float or Horticultural glass.

It is not recommended for use as a replacement for a broken pane in a sash glazed with original mouthblown glass.

We can provide both categories of glass in laminated form to comply with safety regulations for doors and low level windows.