Glass has been produced in various forms for thousands of years. The three main ingredients are sand, silica and soda which, when heated and cooled rapidly, fuse to form a hard, brittle and transparent material. The invention of float glass by the Pilkington brothers in the 1950’s allowed large perfectly flat and blemish free sheets to be produced. Further developments in processing technology have reduced the cost of glass and increased the range of possible applications. Today, by adding further ingredients or altering the processing method, glass is used for variety of applications from correcting poor eyesight to stopping a bullet.

Common glass issues

Toughened safety glass

Toughened or tempered are terms used to describe safety glass which is processed using controlled thermal or chemical treatments to significantly increase its strength. Toughened safety glass in used in the production of almost all shower doors and enclosures. Acrylic sheets are still used for some specialist applications such as boats and assisted showers. It is worth noting that glass cannot be cut or drilled once it has been toughened.

All shower doors sold in the UK and Europe must comply with the European safety standard for glass EN12150 which applies to toughened glass used in construction and furniture. EN12150 replaced the British standard BS6206 in September of 2006 and applies only to glass manufactured after that date; usually the safety standard or the word ‘tempered’ is etched onto the corner or edge of the glass.

Toughened safety glass is not shatter resistant rather it is designed to shatter into small pieces of no more than 5mm in diameter. Although the broken pieces of glass are still sharp and will cause small cuts the risk of serious injury is vastly reduced due to the absence of large shards. The surface of toughened safety glass is highly resistant to impacts and although it may still be marked a great force is required for it to shatter. The edges of the glass are, however, vulnerable and a slight shock can cause it to shatter because of the surface tension that provides strength.

Shattered and chipped glass

Impacts are the most common cause of shattered glass. Modern shower enclosures are defined by exposed sheets of glass with little or no framework protecting exposed edges. Once the shower enclosure is installed it is perfectly safe but great care should be taken when handling and installing glass panels. Almost all bathrooms have tiles or a similar hard surface covering; the edges and especially the corners of the glass are particularly vulnerable and impacting the wall or floor will often cause the glass to chip or shatter.

When installing a glass panel it is advisable not to allow the exposed edges to come into direct contact with the tiled floor or walls. Clear rubber pads are commonly used as a cushion between the bottom of the glass and the floor, the pads can be trimmed flush with the glass before silicone sealant is applied and will be invisible after installation. If glass is in direct contact with a hard surface any movement, such as slight flex in the floor or movement in the glass when the shower door is opened, may cause rubbing and the glass to shatter.

When glass shatters the surface tension created by the toughening process is released as energy which will propel the small pieces of glass outwards resembling a small explosion. As the thickness of the glass increases so does the tension contained within. If the shower enclosure glass shatters the entire room should be swept to remove the bulk of the debris and then thoroughly vacuumed and washed down to remove any remaining splinters. The damage shower panel will have to be replaced and the shower tray may also be chipped or scratched by the debris.

On very rare occasions glass can shatter for no obvious reason. This occurrence can happen to any glass in the home and does not necessarily indicate that the shower enclosure, window or door is faulty. Breakages of this nature, including any resulting damage, should be covered by house hold insurance although the manufacturer should also be informed. The manufacturer may choose to inspect the panel for defects or possible causes.

Bowed glass

The toughening process applied to safety glass creates tension in the surface which may on occasion cause the glass to curve upwards along its length creating a bow. Almost all toughened safety glass has some small degree of bow, typically 1 or 2mm for a shower door. The degree of bow can be measured by placing a long spirit level vertically against the surface. A small bow will not normally cause any issue with a shower door or even be noticeable to the naked eye.

Occasionally a greater degree of bow will be present and this can cause problems with semi-frameless or frameless shower doors where the leading edges of panels seal against each other. If the glass bows into the shower enclosure a gap between sealing profile may be visible in the centre of the panel and if the bow is to the outside gaps may be seen at the top and bottom of the panel. Water will often leak from gaps between the sealing profiles and the glass may need to be replaced to cure the problem, this should be covered by the manufacturer’s warranty.

Bubbles and inclusions in glass

The process of producing glass requires it to be heated to a molten state. Occasionally tiny bubbles of air can be trapped or burst through the surface. Trapped air in the glass will be visible on close inspection as will tips or holes where the air has escaped through the surface.

The term inclusion is used to describe foreign particles such as dirt or grit which bond to the glass when it is in a molten state. Inclusions are often visible when the glass has cooled either suspended within the inner layers or on the surface. This type of fault cannot be repaired and replacement should be covered by the manufacturer.

Scratches and blemishes

Although the surface of toughened glass is very hard it can be scratched or marked. Light marks and blemishes, may be removed by polishing with Jeweller’s Rouge, a fine iron oxide powder which is mixed with water to produce an abrasive paste. Applied with a soft cloth or polishing wheel, Jeweller’s Rouge softens the sharp edges of scratches that reflect light and make them visible. Light blemishes which appear as white marks may also be polished away using this method. Deeper scratches and blemishes cannot normally be removed and replacement of the glass will be the only course of remedial action. Scratches and blemishes that are visible when the shower enclosure is inspected before installation should be covered by the product guarantee. After installation scratches and blemishes may be attributed reasonably to wear and tear and will therefore not be covered by the manufacturer, always inspect a new shower enclosure carefully before installation.

Marks visible in the surface of etched or sandblasted glass

Etched or sandblasted glass is often referred to as modesty glass due to its opaque appearance which is achieved by roughening the polished surface with a chemical or by using a high pressure jet of fine sand. Scratches and blemishes cannot be removed by polishing and damage of this nature will require replacement of the glass. Often etched or sandblasted glass is sealed with a chemical anti-lime scale coating to protect the surface from grease and finger marks which appear as dull areas and can be difficult to remove. This is not a fault with the glass and marks can be removed with a dilute solution of warm soapy water and a soft cloth. Contact the manufacturer of the shower enclosure for advice regarding the best way to remove greasy marks.