ico The history of glass blocks
  The origins of glass blocks

Glass blocks have been used for over a hundred years as a building material, where translucence and durability are important. Other earlier names were ‘cellular glass’, and also ‘glass brick’ – a name, which is sometimes still used. The latter is used in rectangular sided forms for wall construction, as bricks in a wall. In the XIX century there was progress in the building industry – the dominant place of the earlier wood and stone was taken by steel and cast-iron. During the same period the effectiveness of glass production also increased and so did the interest in glass blocks.

The term ‘concrete glass’ originates from the German firm Deutsche Luxfer, which in 1907 patented the method of producing glass blocks. As the glass was relatively thin, for greater durability the blocks were mounted in a stronger frame construction, which resulted in wide wall surfaces between glass blocks. And thus this same method came to be known as ‘concrete of glass’ and so arose the erroneous expression. And therefore now the name generally used for the product is ‘ glass block’. Two halves of a glass block, which are joined together.

Earlier constructions of glass blocks

In the beginning glass blocks were used as skylights in cellars and on roofs, then in the form of vaulting. glass blocks were produced as prefabricated items in factories and then transported to the building site. In the first half of the XX century, glass blocks were extensively applied to this type of vaulting and in cellar windows, however in the sixties of the XX century glass blocks began to be used in other constructions such as staircases, skylights in the facades of industrial buildings etc.

Slaughterhouses, bakeries, petrol stations, workshops and kiosks are another type construction where glass blocks of frequently used for their durability and ability to conceal the activities inside the building. However this type of vaulting construction disappeared, because it was difficult to seal it. Leaks were the rule rather than the exception. In many places in Europe many glass blocks were covered and walled over because of the threat of collapse and leaks.

In Europe glass blocks were widely used in the construction of underground railways. In cities such as Paris and London glass blocks were used to allow light onto the underground railway line. For example in London, practically all over the city, one may still see pavements made from glass blocks.

Glass blocks – examples of former craftsmanship

At the beginning of the forties of the XX century the work of a glass block mason was considered to require higher qualifications than the remaining types of building work and it was difficult to find such work. Most often it was the most able and those with contacts, who secured such employment. In those times a special mortar was used, and the contemporary mortar is derived directly from its, however with improved components. In vaulting, first a wooden form was erected, and then the walling of glass blocks with reinforcement, more or less the same as for bricks.

Contemporary construction does not differ greatly, only in that most frequently little masons’ crosses are used on the grouting for its straightening, in order to obtain straighter grouting and the ability to lay more layers in a day. The Block Lock adhesive system, which currently dominates the European market, first saw the light of day in 1997, and thus the progress observed its that time is significantly greater than that from the beginning of the XX century until 1997.

Models and patterns of glass blocks

For virtually a hundred years glass blocks, to a very large extent, have looked the same, with the same patterns and with some several colours. Initially each producer of glass blocks at his own dimensions, but over the years an unofficially standardised form has emerged for dimensions and thickness. North America continues to retain its ‘ inch’, which is somewhat larger and thicker comparison with European glass blocks and with the remaining parts of the world. From the late seventies of the XX century the standard dimensions in Europe are: 19 x 19 x 8. Once knurling was the dominating pattern of concrete glass, after which immediately followed declaration expressed in the form of clouds. This latter type is regarded as standard today.

With the passage of time many patterns of various producers have appeared and disappeared, enjoying great popularity from the end the fifties to the mid sixties of the XX century. Colours did not exist except for bronze, which was frequently used in cellars and vertical skylights in detached houses. There were also several periods with the painting of glass blocks by various artists, but in time this passed away. Now there are definitely more colours and patterns of glass blocks available, and thus there are patterns with turtles, waves, bubbles, rainbows and with trellises and about fifteen different colours in various shades. Lastly and absolutely the greatest novelty in the glass blocks sector are the new Metallic glass blocks from the Italian firm Seves. There reflective wrapping appears around the glass blocks, instead of the usual white painted surface. This causes the glass blocks to take on an entirely different lustre than traditional glass blocks. And as it could have been expected these are the favourite glass blocks of architects. They also appearing in 10 different metallic colours special models.

The second greatest novelty of many years is Pegasus – a new form of glass block from the Italian firm Seves. These new glass blocks allow one to achieve a joint of only 2 mm during building, but with the same stability. With the Block Lock adhesive system the width of joints of Pegasus blocks is also 2 mm.

Glass blocks today and in the past

During the seventies the demand the glass blocks fell significantly. This was due in a great extent to the product range, which all looked the same as it did at the beginning of the XX century, and also because of the energy crisis, which appeared at the start of the seventies of the XX century, when industry sought more energy-saving materials. Then glass blocks gained a bad reputation for energy consumption, though in principle they did not differ in this regard from conventional windows. In the nineties of the XX century glass blocks return to favour, becoming the great favourite of architects. All fashionable and ambitious architects wished to have glass blocks in every second construction. Bars, partitions in conference halls, floors and ceilings – in principle for all possible solutions.

The great renaissance is to a large extent possible due to the new patterns and colours already referred to, which have brought glass blocks a greater popularity, not only among architects and investors. Architects have encouraged other uses of glass blocks in buildings than only on staircases and the facades of industrial buildings. The glass blocks have made themselves at home in ordinary buildings. Beginning with large numbers in bathrooms in the form of shower walls, and in later years in all rooms as partitions, skylights in kitchens, stairs etc. The great increase in the numbers of shower walls made of glass blocks has to a great extent been caused by the Block Lock adhesive system, which was first introduced in 1997.

This with the simultaneous appearance of the enthusiasm for “do it yourself” had the effect that building walls of glass blocks became simpler and easier than ever before. A continuous progress may be observed in the area of glass blocks and additives. This will have the effect that glass blocks shall return in new constructions and their surroundings for a long period in the next century hundred years