FAQ: Glass

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What is glass anyway? (Definition)

Glass is an inorganic melting product and is made from quartz sand, soda and lime. It essentially solidifies without crystallisation. Glass is a "tough (subcooled) liquid".


What is flat glass?

The modern float glass manufacturing process has now replaced almost all earlier flat glass manufacturing processes. Float means "swimming on top" or "drifting", whereby the very principle of this method is also characterised. 
In the float process, an endless glass strip moves from the melting tank on a liquid tin bath, where it floats on the surface of the molten metal, spreads and is kept at a sufficiently high temperature for an adequate length of time. As a result of the surface tension of the glass melt and the flat surface of the tin bath, an absolutely flat-parallel glass strip is formed in a natural way.
In the cooling channel and on the subsequent transport route, the glass cools down to room temperature so that it can be cut into panels.


What is patterned glass?

GM PATTERNED GLASS is glass manufactured by a machine rolling process. It is produced colourless or coloured, without or with a wire mesh inlay, with a structured surface on one or both sides. It is translucent, but only transparent to a limited extent.


How should glass surfaces be cleaned?

Glass surfaces must be cleaned regularly, although the frequency depends, of course, on the degree of soiling. The best way is to use lots of clean water and simple soft cloths or sponges. In addition, commercially available spray cleaners may also be used.

However, alkaline detergents and acids as well as agents containing fluoride should not be used. Grease and sealant residues are removed with commercially available, non-aggressive solvents (methylated spirit, isopropanol), after which you should rinse with plenty of water. Separate provisions for cleaning apply to special types of glass (sun protection glass, etc.).


What is the maximum measure for GM TSG SECURMART® safety glass?

The maximum dimension is 2,460 x 5,900 mm.


Is glass also suitable as a material for stairs?

Yes: LSG made of TSG.


Is glass suitable for use as a back wall/cover for kitchens?



What special edges are available at Glas Marte?

The special edge GM CONTOUR® is especially suitable for kitchen covers with a glass thickness of 12 mm. The edge is much more resistant to mechanical influences (impact) than other glass edges. Any type of float glass, safety glass or GM TSG COLORMART® can be machined with this edge.


What are the advantages of GM TSG SECURMART®?

  • increased impact and shock resistance
  • increased flexural strength
  • increased temperature change resistance
  • low risk of injury


What is insulating glass?

The term insulating glass is defined in DIN EN 1279:

Multi-pane insulating glass is a glazing unit made of two or more glass panes (window glass, mirror glass, cast glass, flat glass) separated by one or more air or gas-filled spaces.


What are the benefits of insulating glass?

Thanks to the use of different basic products and different special gas fillings, it is possible today to produce building-specific, individually suitable multifunctional glass. We distinguish between function and area of use.

Function: Thermal insulation, sun protection, sound insulation, safety, burglary protection, design/optics, wind and weather protection, illumination, shading.

Areas of use: Living and office rooms, roof glass, accessible and walkable glass, facades, gymnasiums/sports facilities, with avalanche pressure, all-glass corners/all-glass joints.


Why can condensation form on window panes?

  • Inner condensate: Panes can fog up when they are colder than the air around them and this air also contains a lot of moisture. If warm moist air meets the cold pane, the air cools and gives up some of the water vapour to the surface. In order to avoid this effect as much as possible, Glas Marte recommends the installation of thermally insulated spacer profiles in combination with triple insulating glass. The moisture content in the room air must be kept as low as possible by regular, proper ventilation. For example, in the passive house through controlled aeration and ventilation.
  • Outer condensate: This is caused by the cooling of the outer panes in the night hours. The effect is further supported by the very good insulating effect of the triple insulating glass. As soon as the morning sun heats the outer pane again, the outer condensate is dried up immediately.


How is sound insulation achieved?

Sound insulation is achieved by constructive measures or their combination:

  • asymmetrical glass construction
  • wider spacers
  • Use of laminated safety glass with sound insulation foil


Does the spacer in sound reduction glass have an influence on the sound insulation value?

Yes. The wider the spacer, the better the sound insulation.


Can special glass make better use of solar energy?

Glass is the only building material that makes the use of free solar energy possible. Regional building regulations also take this into account with the introduction of the so-called "solar gain". For this purpose, it is necessary to select an insulating glass with a tailor-made energy input, so that heat gain and thermal insulation help to save heating energy.


Is insulating glass available with cross bars?

Basically, there are two types:

  • Visible cross bars in insulating glass. This prevents contamination of the cross bars and allows uninterrupted cleaning of the glass surfaces.
  • Bars in insulating glass. Here, the window manufacturer glues cross bars to the glass. The cross bars therefore have a dividing effect on the glass.


What is the g-value?

The g-value (total energy transmittance) is a variable that is only meaningful with glass. It is the sum of the radiation flow that is directly let through and the secondary heat dissipation of the glazing to the inside. The g-value is determined according to EN 410 and expressed in %.


What is the U-value?

The thermal transmission coefficient (U-value) is the central unit of measurement for the heat loss of a component. It indicates how much heat per unit of time passes through 1 m² of a component if there is a temperature difference of 1 Kelvin between the two adjacent sides. The smaller the U-value, the better the thermal insulation.
The Ug-value is the thermal transmission coefficient of glazing. In accordance with DIN 4108-4, it is either calculated according to EN 673 or measured according to EN 674 or EN 675. The unit of measurement is W/m²K.


What is the colour rendering index?

The general colour rendering index Rα indicates the influence of spectral transmission on the colour recognition of objects in a room glazed with insulating glass. It is determined in accordance with EN 410, taking into account a reference light type of the same or similar colour temperature.


What is the UV transmittance coefficient?

The UV transmittance coefficient is the transmittance in the wavelength range from 280 nm to 380 nm in relation to the incident solar radiation in this range (EN 410).


What is light transmittance?

The light transmittance is determined in accordance with EN 410 for the radiation range from 380 nm to 780 nm in relation to the standard light type D 65 according to DIN 5033, part 7, and to the light sensitivity of the human eye.


What is light reflection?

The light reflectance factor indicates the percentage of the visible light that is reflected in the wavelength range of about 380–780 nm at the surface of the glass pane.


What is emissivity?

Emissivity is the measure of a surface's ability to release absorbed heat again as radiation. With normal float glass, ε = 0.84, i.e. 84% of the heat absorbed is radiated again.

In the case of thermal insulation glass, one side is coated wafer-thin with precious metal. This low-emissive or "low-E" layer reduces emissivity to 0.03 for today's standard glass types and to 0.01 for top products. In this case, only 1% of the heat radiation is released to the outside on the coated side and around 99% is reflected back into the building. At the same time, this significantly increases the surface temperature of the inner pane and thus the feeling of comfort.


What is the Psi value (Ψ)?

The use of thermally optimised spacers leads to additional energy savings and an improvement in the indoor climate. The thermally improved edge seal reduces heat losses in the transition area from the glass to the window frame. These thermal insulation properties are expressed by the Psi value. This is a length-related thermal transmission coefficient that describes the thermal bridges of a component. In the case of windows, these thermal bridges consist mainly of the interrelationship of window frame, insulating glass (and its spacers) and the glass inset in the window frames. That means: The Psi value (Ψ) is meaningfully determined for the system (frame + insulating glass). A separate consideration of the Psi value for the individual components (glass, spacer, etc.) is not constructive.


How can thermal cracks be prevented?

Floating glass surfaces must be kept free from heat accumulating objects such as: foils, furniture, objects on the glass, radiators, columns, partial shading and much more. If this cannot be complied with, toughened safety glass or LSG made of heat strengthened glass must be used.


What is the minimum space between glass and furniture to prevent thermal cracks?

To prevent thermal cracks, we recommend a minimum space of 30 cm between the insulating glass pane and the furniture/objects.


From what altitude does insulating glass have to be produced with low pressure?

Glas Marte provides insulating glass with low pressure for installation from an altitude of 1,000 m above sea level. Two execution options are available:

  • Low pressure: The pane is produced in such a way that both delivery and installation can take place without breakage.
  • Pressure compensation valve: Here, the air pressure compensation must be done by the window manufacturer both on the transport route and at the installation site.


If it is recommended to work with TSG with all-glass joints/corners?

Glas Marte recommends the execution in TSG for this application for several reasons:

  • coverage of the joint/corner area with enamel strips is possible
  • often required in accordance with statics or construction law anyway
  • thermal cracks can be excluded in this way


Do enamel strips that cover the edge seal have to be black?

Enamel strips that cover the edge seal do not necessarily have to be black. If overly bright colours are used, however, the edge seal can shine through and the required UV protection is lost. We recommend the execution in black.


Should the middle pane of roof glazing be made of TSG?

The middle pane does not necessarily have to be made of TSG. However, since the risk of breakage due to thermal influences is much higher in the roof area, Glas Marte recommends that the middle pane be executed in toughened safety glass.


Can thermal cracks also occur in sun protection glass?

With sun protection glass, there is by all means a possibility that thermal cracks will occur. In particular, stained (absorbing) glass is generally to be executed in TSG.


What types of GM SLIDING SYSTEMS are there?

There are bottom mounted systems (GM LIGHTROLL®) and top-hung systems (GM TOPROLL®).


What glass thicknesses/glass types can be used in the sliding systems for balcony glazing?

The Glas Marte sliding systems use glass thicknesses from 6 to 24 mm. There are sliding systems for both toughened safety glass (TSG) and for laminated safety glass (LSG/TSG/HSG). Due to the combination of locking pin (bolt) and bonding, there is no crushing of the foil. This excludes sagging (decrease in clamping effect).


Up to what height can the Glas Marte sliding systems be used for balcony and loggia glazing?

The sliding systems from Glas Marte can be used for element heights up to 3,200 mm.


In what surface finishes are the profiles available?

The Glas Marte systems are available in  natural anodised (EV1) and C31-C35 anodised finishes as well as in all standard RAL coatings (special colours after clarification).


Does balcony and seating area glazing provide sound insulation?

Yes, depending on the execution, significant sound insulation improvements are possible.


How many levels of sliding glazing are possible?

1, 2, 3, 4 and 5-track executions are possible, therefore an opening possibility of a maximum of 80% of the balcony is possible.


How is the drainage of the balcony sliding systems done?

Superficially, via drainage slots in the visual area (no closed chambers).


Are balcony sliding systems from Glas Marte impervious?

No, because this glazing is frameless cold glazing. They offer good protection against wind and weather and prolong the season, but are not comparable with windows.


Does Glas Marte have frameless sliding systems?

Yes, frameless sliding systems are used for balcony, loggia and patio glazing.


Up to what widths can the individual sliding glass panes for the balcony be executed?

1/3 of the installation height is recommended. However, the weight-related rollers and the maximum loads per system must be taken into account.


Are the balcony sliding systems lockable?

Yes, the systems for balcony glazing can be locked with pressure cylinder locks or locking bolts.


Can the brushes freeze up on the sliding systems?

This can virtually be ruled out, as all profiles are made with concealed internal brushes.


Are the sliding elements smooth-running? What quality is used for the drives?

Thanks to the plastic-coated stainless steel ball bearing rollers, easy and silent movement is possible.


Are there also folding systems for balcony and loggia glazing at Glas Marte?

No, we prefer pure sliding systems, as they are easier to install, more variable in terms of opening and save space.


Can Glas Marte sliding systems also be used for shading?

Yes, the GM LIGHTROLL® and GM TOPROLL® sliding systems can be used for shading.


Are there balcony sliding systems especially for renovations of facades?

Yes, Glas Marte developed the GM TOPROLL® PARAPET system for this. The parapet glazing in this system conforms to DIN 18008.


Does a balcony glazing from Glas Marte have a rear ventilation system?

Due to the overlapping of the sliding glass panes (50 mm), constant rear ventilation takes place.


What maximum glass weights can Glas Marte sliding door systems accept?

Depending on the system, glass weights of up to 200 kg can be executed.


Are the glass panes mechanically secured in the top-hung sliding door systems?

Yes, each sliding glass pane is secured with two bolts in addition to bonding (exception: GM TOPROLL® BALANCE)


Are there sliding door systems at Glas Marte that can be executed barrier-free (no threshold)?

Thanks to the local guide in the edge area, all Glas Marte sliding door systems offer a barrier-free passage. Large openings can be executed without a threshold, for example with the GM TOPROLL® 10/14 inner system.


Are Glas Marte systems available with a soft stop (damping)?

Yes, the GM TOPROLL® 100 and GM TOPROLL® BALANCE systems are can be executed on one or both sides with a softstop.


Which sliding door system has the lowest installation height?

The GM TOPROLL® SMART system has an installation height of just 40 mm.


Which sliding door system can be mounted on both ceiling and wall?

GM TOPROLL® 100 is the right system for these applications.


What handle variants are available?

There are round stainless steel shell handles with a diameter of 55 mm, angular stainless steel shell handles (40 x 100 mm), G-handles and bar handles made of stainless steel.



Are there holding systems with general building authority approval (abZ)?

Yes, the GM OVERHEAD system for glass canopies has and general building authority approval with the approval number Z.70.3-103. There are 3 approved holder diameters: 45, 60 and 80 mm.


What outer diameters do the smallest and largest point holders have?

The smallest raised holder is GM PUNTO® 13 (diameter: 13 mm), the largest is GM PUNTO® 36 (diameter: 36 mm). The smallest flush-mounted holder is GM PICO® (dia. 20/28). Larger variants are the movable and height-adjustable GM PICO® KING point holding system with a diameter of 36 mm and the articulated GM PICO® LORD, also with a diameter of 36 mm.


Does Glas Marte have flush-mounted holders?

Yes, from 20 mm in diameter to 36 mm in diameter.


Is there a Glas Marte luminous ceiling systems for glass?

Yes, the GM KUB and GM SOB luminous ceiling systems are available.


Are there systems for fastening kitchen splashbacks and glass cladding?

Yes, the GM PICO®GM PICO® KING and GM PICO® LORD flush-mounted point holding systems.


Does Glas Marte have a glass canopy system?

Yes, with GM OVERHEAD, Glas Marte has a canopy system that has a general building authority approval in Germany. With the general building authority approval, a canopy with the dimensions 1,800 x 4,080 mm can be realised.


In which surface finishes are the profiles from Glas Marte available?

The Glas Marte systems are available in natural anodised (EV1) and C31-C35 anodised finishes as well as in all standard RAL coatings (special colours after clarification).


Does Glas Marte have frame profile systems for glass doors and glass walls?

Yes, the GM FRAME PROFILES are available for glass doors (incl. fixed parts) and glass walls. Thanks to the reduction to just two profiles for different glazings, the installation is as simple as could be. With an installation depth of just 40 mm and a facing width of just 22 mm, slender and yet incredibly stable glazing can be realised.


Does Glas Marte have overlapping (shingle-like) glass facade systems?

Yes, for example the GM BRACKET S glass edge holding system. The holder is designed for the use of TSG or LSG with thicknesses of 8 – 12 mm.


Can AUTOCAD (DWG or DXF) files be processed?

Yes, we are happy to make these available to our customers.


Where can I buy GM SYSTEMS?

As a processor, you can purchase the GM HOLDING SYSTEMS directly from Glas Marte. For private customers, Glas Marte has a wide network of partner companies. Contact us, we will be happy to provide you with the details of a specialist dealer in your region. In Vorarlberg we also carry out installations ourselves!


Can I get qualified know-how on site as a specialist company or architect?

Yes, through our sales representatives or on one of our training courses.


Can I take part in a training course as a specialist company or architect?

Yes. We regularly hold training courses on our products. More information can be found here.


Where can I get documents on GM HOLDING SYSTEMS?

In our download area you will find brochures, tendering texts, detailed drawings, enquiry and order forms, installation instructions and other useful materials.


Are sample systems/hand samples available for your systems?

Yes, they are offered at very reasonable prices. You can order samples here.


How can I obtain a price for a GM RAILING® GLASS RAILING?

We'll be happy to prepare an individual quotation for your building project. Please send your enquiry to railing.anfrage@glasmarte.at – you will receive an exact price for your specific application in a very short time. As a registered customer, you also have the option to use our online calculator for GM RAILING® UNI for calculation. You can find it in our service portal.


What are the key advantages of glass railings?

  1. All-glass railings are safe. The smooth glass surface without uprights, cross bars and pillars reduces injuries of all kinds. It makes it difficult for children to climb up and over, and they don't usually have any desire to do so anyway due to the transparency. Older people prefer the bright floor surfaces without shadows and the clarity.
  2. All-glass railings protect. Sound insulation and wind protection are highly valued in glass railings.
  3. Aesthetics. Glass railings take a back seat visually and show the space, not the barrier. They are light, modern and open to views, non-verbal conversation and light.


How are individual designs, special shapes and curved elements implemented?

GM RAILING® is planned and manufactured individually for the respective application (exception: standard formats with shortened delivery time). Most special shapes and designs are possible.

Bent glass railing elements can be implemented in particular with the BENT system. A separate test is required if the bending radius is less than 2,500 mm. Bent elements in the stair area (e.g. spiral staircase) cannot be realized with GM RAILING®.


In which installation situations is GM RAILING® used?

The GM RAILING®  glass railing system is primarily used as anti drop device. In addition, the following applications are implemented with GM RAILING® systems:

  • "glassy" fence, with sight screen, wind protection, splash water protection and sound insulation properties
  • Glass advertising and labelling surfaces, building control systems, columns or signs
  • Glass wall, floor-to-ceiling
  • Glass clamping is a very popular method that is used in particular in structural glass construction.


What scope of services does Glas Marte offer for GM RAILING®?

  • Advice on planning and implementation
  • Technical drawings or text descriptions
  • Quotations
  • Location-based clarification
  • Work planning and execution planning
  • Submission of approval plans
  • Static proofs abP (general building authority test certificate) and tests
  • Individual production on the basis of the granted approval
  • Manufacturing and delivery
  • On request also installation or installation support


What is the maximum glass height of GM RAILING®?

The maximum glass height can far exceed 1 metre. Depending on the system and the loads, these cases are checked by our technicians. In most cases, a corresponding handrail must be attached at the legal height.


Is GM RAILING®  possible without a handrail?

In principle, GM RAILING®  can also be executed without a handrail. This must be stated at the time of ordering. With our GM WINDOORAIL® FRAMELESS French window, no edge protection or handrail is required according to the general building authority approval Z-70.5-201.


What speaks in favour of a handrail with GM RAILING®?

Glass railings with a handrail are prescribed above all in Germany. This has the following advantages:

  • The handrail serves as an edge protector.
  • In the event of a parapet element failure, the handrail is of decisive importance for the residual stability.
  • When using railings outdoors, unavoidable delamination of the laminated safety glass can occur. Through the attachment of a handrail, the upper edge is covered and this risk is consequently reduced.


Which versions of the handrail are possible?

GM RAILING®  offers numerous handrail variants. In addition to stainless steel profiles, ground or polished, there are wooden sheathings in various shapes and types of wood as well as handrails made of aluminium. A glass edge protector made of borosilicate (GM GLASS STRIPE) can also be installed in the factory.


What ways exist to reduce soiling?

GM RAILING® can be manufactured with the UNICLEAN NANO surface sealing. The dirt adheres less to the glass surface and can be removed with less cleaning effort.


What design options are available for GM RAILING®?

GM RAILING®  can be designed with colour foils, screen printing or enamelling. In addition, sandblasting, the use of LEDs (powerglass) or the embedding of photovoltaic cells are possible.


Can I also purchase GM RAILING® without glass?

GM RAILING®  is completely and extensively tested with glass and profile, prefabrication is automated and manufacturing takes place with the highest process accuracy with a production line manufactured using special mechanical engineering. The special feature of Glas Marte glass railings is the full-surface bonding of the glass module and profile in the factory, which enables void-free, stress-free glass support. For this reason, it usually makes no sense to supply only sub-components.

The choice of glass type as well as the required glass thicknesses correspond to the series and requirements. You are relieved of this choice, the checking of the quality and the static and production correlations with a complete delivery of GM RAILING®.


How long is the delivery time for GM RAILING®?

In the case of GM RAILING® with extensive execution plans etc. as well as the usual clarification periods, a delivery time of about 5–7 weeks must be taken into account.


What length of installation time has to be taken into account?

The installation time for GM RAILING® is only a fraction of that of a conventional point-held or screwed glass railing. The installation times for the substructure are highly dependent on the geometric situation, the construction condition, the construction accuracy and so on. The assembly time for installation and adjustment is a few minutes per metre, plus the handrail assembly and the installation of the metal sheets.


How does the adjustment of GM RAILING® work?

GM RAILING® is simply, quickly and precisely adjustable in the tenth of a millimetre range with threaded screws. Depending on the series, the corresponding fixation of the adjustment is then required.


Why are glass breakage tests so important in Germany?

  • According to DIN 18008, the effects of damage to any parapet element (including the failure of end panes) must be demonstrated.
  • In case of a parapet element failure, especially in the case of interaction of handrail and broken glass, this can best be verified by means of tests, as the results of breakage tests differ drastically from one another depending on the choice of glass (LSG made of 2 x TSG, LSG made of 2 x HSG or LSG made of 2 x float glass) and the foil thickness.

The broken glass has in some cases a residual stability and a residual load-bearing behaviour. Depending on the type of glass, this can have a positive or negative effect on the overall system.

To date, we are not aware of any method by which the residual stability of broken glass can be proven conclusively by means of calculation. For this reason, GM RAILING® has carried out hundreds of glass breakage tests with original components up to a single length of 4 m. Find out more about our quality assurance!


What do I do in case of a glass breakage?

  • According to DIN 18008, the effects of damage to any parapet element (including the failure of end panes) must be demonstrated.
  • In case of a parapet element failure, especially in the case of interaction of handrail and broken glass, this can best be verified by means of tests, as the results of breakage tests differ drastically from one another depending on the choice of glass (LSG made of 2 x TSG, LSG made of 2 x HSG or LSG made of 2 x float glass) and the foil thickness.

The broken glass has in some cases a residual stability and a residual load-bearing behaviour. Depending on the type of glass, this can have a positive or negative effect on the overall system.

To date, we are not aware of any method by which the residual stability of broken glass can be proven conclusively by means of calculation. For this reason, GM RAILING® has carried out hundreds of glass breakage tests with original components up to a single length of 4 m. Find out more about our quality assurance!


May the glass railing subsequently change its position?

No. GM RAILING® is glued so that, even with large deflections in the profile area, an air gap between the glass and profile into which wedges, dirt, pebbles or the like could slip is prevented. In addition, rubber parts cannot be shifted.