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Glass Standards for Use in Museums and Galleries

The glass industry has a number of standards which are used to specify the level of protection afforded by glass. Outside the industry there are widespread misunderstandings about the qualities of the different glazing options. This guide sets out to explain the standards and their relevance in museum and gallery applications.

There are three standards which are directly relevant:

1. BS6206: 1981 (1984)
Specification for impact performance requirements for flat safety glass and safety plastics for use in buildings

Probably the most commonly used standard. The aim is to provide a standard for glass that will break safely in the event of a soft body impact. Introduced as a result of accidents, particularly to children involving patio doors and doors with glass panels. Although not relevant to security aspects it is particularly relevant to public safety.

The British Standard test consists of a bag containing ball bearings weighing 45kg which is swung on a pendulum at the glass sample. A pass is achieved if the glass breaks safely - it does not have to remain intact.

The most commonly used material is heat toughened glass, which will disintegrate if attacked with a sharp instrument. Laminated glass usually 6.4mm is also used for this purpose, but will not withstand a physical attack, for example with a hammer.

2. BS5544: 1978 (1994)
Specification for anti-bandit glazing (glazing resistant to manual attack)

This is the UK standard that is applied for anti-intruder glazing. The standard has been developed to represent an attack by a blunt instrument, ie a hammer. The test comprises five drops of a steel ball weighing 2.5kg from a height of 3m. Then one further drop on to a separate sample from 9m. The ball must not penetrate the glazing in either test. It is a straight forward pass or fail test. It does not attempt to define the number of blows or the time required to achieve penetration.

There are a wide variety of materials which will meet this standard. As an example one manufacturer has a 4mm product, comprising 3mm float glass and polyester laminated to the protected face which will pass this test. However, the most commonly used materials for this type of application are 11.5mm 3-ply laminate or 11.3mm 5-ply laminate, which give a realistic resistance to penetration by blunt instrument attack.

3. DIN52290 Part 3: Anti-Bandit

This is a German standard and is the first attempt to replicate scientifically a physical assault using a repeatable test. It is expected that it will form part of a proposed European standard (pr EN356) which will feature eight categories of anti-bandit glazing with a number of different testing procedures.

The test comprises of a hydraulically driven axe head attacking a glass sample. The intention being to cut a 400mm square in the test piece. Each blow is delivered with the same level of energy (not achievable by a human) and the axe head is sharpened every ten blows. It is a very severe test. The sample is classified by the number of blows required to cut the 400mm square - 30+ is Class B1, 50+ is Class B2 and 70+ is Class B3. For the majority of applications DIN52290 Part 3 Class B1 is sufficient.

There are essentially two types of laminate available which will meet DIN52290 specification. In an all glass laminate materials would be a minimum of 18mm thick and weigh 40+kg/mē. With a glass/polycarbonate/glass laminate the thickness is reduced to 14mm and the weight to 27kg/mē. The glass/ polycarbonate/glass construction has a better overall performance but the cost is greater.

Framing and Securing

The levels of energy that the materials described above can absorb is considerable. Glass polycarbonates will resist penetration by a powerful man using a fireman's axe. However, the glass is only as good as its mounting and securing. The protection afforded by these products can be optimised by looking at the system as a whole.

To achieve this optimisation there are a number of rules to follow:

  • An adequate level of edge cover for the glazing - typically 25-30mm.
  • The glazing to be secured into the frame with a suitable bonding agent such as a compatible neutral curing silicon.
  • The frame needs to be securely fastened within the particular application ie the walls if used for secondary or primary glazing or the total framing system in a display.
  • The glass to be framed on all four (or however many) sides. Specialist advice should be sought if this is not considered possible.

Glazing Options

Laminated glass offers a wide range of options and product can be tailored to the particular needs of the customer. In addition to controlling the thickness of the glazing the material can be constructed for example to improve environmental conditions by forming a micro-climate and to eliminate reflection. The use of materials such as polycarbonate or polyester laminated to the protected face gives a "spall free" product. Spalls are the shards of glass which become detached from the protected face of the glass in the event of violent attack or accidental damage, which can cause damage to exhibits.

Further advice can be obtained from Collections Link on 0845 838 4000