Manufacturing

Grinding

Grinding eliminates the cutting edge of glass. It is very important for product safety. It uses a continual flow of water to cool the edge, to avoid tensions in the glass.

Veneto Vetro uses top-performing numerical control grinders, also for exceptional sizes, with especially delicate coatings. For rectangular glass, grinding takes place using bilateral machines. For shaped glass, with special processes, CNC machines are used that can remove and uniform the glass edges, based on the result desired.

Edges can be:

• round shiny thread: the edge is rounded and polished;
• flat shiny thread: the edge is polished and perpendicular to surfaces with a bevelled joint;
• rough thread: this is like the polished thread except that the edge is matt not shiny and is rougher. This finish is used when the glass perimeter is hidden by the frame or window/door;
• 45° grinding: the inclination can change based on design needs;
• bevelled edge: glass edges are ground for 10–40 mm in height with an angle of about 7 degrees compared to the glass surface itself.

Grinding is an obligatory preliminary operation to tempering.

It is sometimes used to limit the thermal shock even though tempering is the most indicated process to limit that phenomenon.

Threading limits the micro surface threading on edges, often the cause of breakage for thermal or mechanical shock. This process is performed on layered glass, assembled in insulating glass panes. Threading makes installing the panel safer for installers as there are no cutting edges. Veneto Vetro recommends this type of process when there is a minimum risk of breakage. Safety is the founding model for Veneto Vetro. Maximum processing sizes are 2700 x 5700 mm.

Drilling

Veneto Vetro has chosen the multispindel numerical control drill to drill glass. Its refrigerated diamond tips create custom-made round or flared holes, slots, notches and cuts to satisfy the most sophisticated design needs. Holes are round when they have the same diameter all over the thickness, flared when diameters change. Maximum sizes possible have a maximum centre distance between holes of 2500 mm, on panes that are maximum 6000 mm in length.

Enamelling

Enamelling is one of the most widespread processes. In interior design and in spandrels it offers interesting aesthetic results, in both modern and classic environments. The ceramic enamels applied are lead-free, a guarantee for the health and safety of environments. For this process, Veneto Vetro uses a two-roller coater that distributes the paint on the surface in controlled quantities, and offers two enamelling types: hot and cold. In the hot one, the ceramic colour is spread on the glass surface and allowed to dry; the colour is incorporated in the glass through the tempering process. This solution lasts longer, guaranteeing life-long colour. First of all, cold enamelling foresees tempering and then colouring done with the two-roller glazer. The colour is left to dry slowly and is not tempered. The result is much more brilliant than hot enamelling. These applications are suited for light, extra-light, coloured, reflecting or printed glass. Maximum glass sizes are 1900 x 5700 mm.

Screen-printing

Screen-printing is the “traditional” system used by Veneto Vetro to spread enamels on glass surfaces, creating personalised solutions. It is performed on flat glass using specific machines and a “screen-printing” frame . The glass can be tempered directly or curved and then tempered.

The screen-printing frame is a very fine, regular, nylon or polyester fabric, spread on an aluminium or iron frame. It is impressed with a negative (film). The fabric’s micro-holes are closed with photo-sensitive gelatine that composes the image.

The print colours pass through the tiny holes of the gaps left by weave threads to the free parts and are deposited on the surface to be printed. This technique requires spreading one colour at a time. Maximum glass sizes are 1800 x 4000 mm.

Tempering

Veneto Vetro is equipped with a top- performing, full-convection tempering furnace, ideal for large, new generation glass, like selective, low emission panes with very low emissions. This type of high level tempering guarantees maximum optical glass quality, an especially important requirement for nautical needs.
Tempered glass can also be subjected to a Heat Soak Test (HST), to reduce to a minimum the risk of the pane breaking spontaneously, due to the presence of Nickel Sulphide particles.

The flat glass is transported on rollers into the tempering furnace at about 640° and, in the next stage, cooled fast by blasts of air. Cooling the surface layers makes it solidify. The inner part stays hot for longer; its cooling produces compression on the surface, balanced by the internal soothing tensions.

Tempered glass is approximately six times more resistant than float glass, because surface defects are kept “closed” by the mechanical compression tensions; whereas the inner part is freer from flaws that could cause cracks. Thanks to that resistance, it is used to make elements with no supporting structures, like glass doors and structural applications. It is considered “safety glass”. Besides being strong, if it breaks it does so into small, smoothed pieces that are not very dangerous.

It is used to make sliding doors, building entrances, bathrooms and showers and interior walls. The tempered glass process and characteristics are subject to standard UNI EN 12150. Safety criteria are linked to UNI EN 7697. Maximum glass sizes are 2600 x 5700 mm.

Technical double-glazing

DOUBLE-GLAZING

Double-glazing is a structure obtained with two or more sealed glass panes, separated by a gap, applied to windows to insulate interiors thermally and acoustically. Structural double-glazing is assembled with the same technique as classical double-glazing; panes can be staggered to allow them to be glued to the window/door to create facades or “continuous” windows, without seeing the uprights, for the “all glass” effect. The silicon sealants used are studied specifically to resist exposure to UV rays. Veneto Vetro assembles really large double-glazing for residential, commercial building needs and for high performance, interior dividing walls. It creates traditional insulating panes, insulating safety panes, insulating structural panes, low emission insulating panes, selective insulating panes, insulating panes with greater sound and heat insulation.

To achieve maximum thermal insulation, Veneto Vetro uses some specific solutions when making double-glazing:

• the air between the two panes can be replaced by noble gases (Argon or Krypton), increasing the thermal insulation considerably;
• one of the two inner surfaces can be coated with a thin, transparent, silver-based layer that withholds heat better in the home;
• the so-called “hot edge” can be applied. This is a stainless steel profile covered with plastic film on the glass supporting frame instead of aluminium, a good heat conductor;
• one of the two double-glazing panes can be coated with a thin film of special noble metal oxides that reflect heat outwards. Besides keeping heat indoors in winter, that system considerably reduces the heat of sun-rays on glass in summer, keeping the interior cooler.

Based on customer needs, Veneto Vetro offers customised solutions using glass and special materials to obtain the best insulation for the specific environment.

To improve sound proofing, it is important to know that:

• when you have two glass panes of a different thickness, their differing vibration helps lower noise;
• glass layered with PVB has sound-proofing properties; the plastic film holding the layering together can have – on request – greater sound-proofing properties than traditional PVB. If two or more films are used for layering, sound-proofing increases;
• with a small channel of about 20 mm you get a better sound-proofing performance.

Maximum glass sizes are 3000 x 6000.

Curved tempered glass

CURVED GLASS AND DOUBLE BENDING

Curved tempered glass is obtained through a gradual heating process to make it mouldable; then, once the desired shape has been obtained, sharp cooling. This product type is used a lot in the shipbuilding sector, on both the outside and internally, as it guarantees maximum visibility and aesthetic result.

To produce curved glass, Veneto Vetro mainly uses vertical tempered bending because it guarantees greater optical quality. As the glass does not run on rollers during the softening stage, it avoids contact with the transport surface, keeping the transfer of small imperfections to a minimum.

In addition to cylindrical bending using its own system, Veneto Vetro creates special bending: from discontinuous bending (glass panes with double curves), to torsion bending, on to slightly rounded glass panes.

There is a big demand for double bending. This process is complex, using concave and convex bending moulds. The result obtained is resistant, high quality, safety glass. During this process, the glass is subjected to a fast heating process. After softening it is pressed fast between a bending mould with concave and convex parts to give the glass the bend desired. Last of all, it is cooled fast. Curved tempered glass is considered safety glass because it creates small fragments when it breaks.

Hardened glass

Veneto Vetro can produce hardened glass. This glass type production procedure is similar to thermal tempering. The difference between tempered and hardened glass is the cooling process, slower in the latter case. Performances are different. Hardened glass is half as resistant to bending as tempered glass, with a lower surface distortion. Hardened glass is used to prevent thermal stress problems, when the safety features typical of tempered glass are not required. Hardened glass is not subject to spontaneous breakage, maintaining the greater mechanical resistance of  annealed glass and lesser deforming of the image reflected.

Large sizes and special processes

The top level preparation of personnel and valuable equipment enable Veneto Vetro to process very large glass items, for each processing stage. From cutting to tempering on to digital printing, processes to satisfy the most ambitious requests made by customers. Machines present in the company can process Jumbo panes, measuring 3300 x 6000 mm each. Along with sizes, thicknesses going from 4 to 25 mm are also the crowning achievement of Veneto Vetro processes. All this is possible through the precious Know-how made available to customers to create special projects requiring commitment, and specific machines. Layered laminar glass is cut on both the upper and lower sides, polymeric film coupling the two panes (in PVB or polyvinyl butyral) is cut using a cutter and a disappearing resistance that melts in the PVB enabling the cut to be opened.