Glazing Guidelines
Viracon requires that only 100% silicone setting blocks be used for all types of glazing systems. The blocks should have a durameter hardness of 85±5. They should also be centered at quarter points and be 1/16" (1.6 mm) less than the channel width (see Figure).

Lockstrip gasket systems also require setting blocks. For additional recommendations, contact the appropriate gasket manufacturer.

Inadequate edge clearances can cause glass breakage as a result of glass-to-frame contact. Viracon recommends a minimum face clearance of 3/16" (5 mm), a minimum edge clearance of 1/4"(6 mm) and a minimum glass bite of 1/2" (13 mm) (see Figure 10).

Weep System
Do not expose the edges of laminated, insulating and opacifier film glass to standing water. This can cause premature seal failure or delamination. Viracon requires either impervious weather seals or an adequate weep system to prevent this from occurring (see Figure 11). This is also true of lockstrip
gasket glazing.

The glazing system manufacturer or designer is ultimately responsible for the design of the weep system and its proper performance.

Structural Silicone Glazing
Structural silicone glazing systems use silicone sealants with an interior backup mullion. It must be specified as a structural silicone glazing system due to compatibility limitations of silicone sealants with certain types of glass or insulating unit secondary seals. To obtain approval for any structural silicone glazing system, contact the appropriate silicone manufacturer or Viracon's Technical Services Department.

Gray Silicone/PIB (Polyisobutylene)
Viracon offers Gray silicone/PIB in addition to standard Black silicone/PIB sealant. Both colors of sealant are the same Dow Corning 982 structural silicone used by Viracon for the past 20 years. Therefore, the structural performance and long-term durability expected of the primary and secondary seal of our insulating glass unit remains the same.

The Gray silicone/PIB dual seal construction has certain inherent visual characteristics that are not readily apparent with a Black silicone/PIB dual seal construction. These include the following:

• Gray color variation. Given the inherent variation in compounding both silicone and PIB by suppliers, visual differences may occur.

• Color match between silicone and PIB. While every effort is made to match these visually, the compounding variation mentioned above precludes a perfect match. Additionally, a slight contrast in color is required in order to identify any sealant inconsistencies.

• Black specks within the silicone and PIB. These are due to the existence of carbon black in the sealant manufacturing process.

• Dark lines or streaks in the silicone. These may occur as a result of the edge deletion process used to remove certain coatings around the perimeter glass edge. With black silicone/PIB these are not visible; however, with the light gray color they may be visible when viewed from close distances.

None of these inherent product characteristics would be considered cause
for rejection.

Glass Handling and Storage
Care needs to be taken during handling and glazing to ensure that glass damage does not occur. Do not allow glass edges to contact the frame or any hard surface during installation. Use rolling blocks if the insulating units are rotated or "cartwheeled" on their corners. To see an example of a rolling block, refer to the Glass Association of North America (GANA) glazing manual.

Improper glass storage techniques may result in damage to glass components, glass surfaces, coatings or glass breakage. Store glass crates properly to prevent them from tipping. Also, ensure proper blocking and protection from outside elements.

Viracon recommends a 5-7° lean against two wide, sturdy uprights, which are capable of withstanding crate weight.

Once the glass is installed, the architect, general contractor or building owner should provide for glass protection and cleaning. Weathering metals, alkaline materials or abrasive cleaners may cause surface damage. Windblown objects, welding sparks or other material that contacts the glass surface during construction may cause irreversible damage.

Maintenance and Cleaning
To maintain aesthetics, it is important to clean the glass during and after construction. For routine cleaning, use a soft, clean, grit-free cloth and a mild soap, detergent, or window cleaning solution.

Rinse immediately with clean water and remove any excess water from the glass surface with a squeegee. Do not allow any metal or hard parts of the cleaning equipment to contact the glass surface.

Take special care cleaning coated reflective glass surfaces. Do not use abrasive cleaners, razor blades, putty knives and metal parts of cleaning equipment, since these will scratch the reflective coating. Fingerprints, grease, smears, dirt, scum and sealant residue are more noticeable on reflective glass, requiring more frequent cleaning. Follow the same cleaning techniques
used for nonreflective glass.

Glass Breakage
It is important to first determine appropriate loads for the glass. Viracon can supply architects with glass strength analyses on specified products. "Unexplained" glass breakage may still occur due to thermal stress, glazing system pressures, glazing damage, handling and storage conditions, excessive wind loads, objects and debris striking the glass, improper factory fabrication or damage by persons or objects at the construction site.

Framing Deflections
Refer to the GANA glazing manual for information on adequate framing systems. You are required to comply with industry standards for framing deflection. It must not exceed either the length of the span divided by 175 or 3/4" (19 mm), whichever is less.

Non-Rectangular Glass Shapes
Viracon's capabilities include cutting virtually any shape glass required for your project without full-size patterns. However, if you require a full-size pattern, it must be submitted to Viracon on mylar material. If not, Viracon will transfer the pattern to mylar at an additional charge. However, Viracon will not be responsible for size accuracy. For additional information, contact Viracon's Inside Sales Department.

Suggested Specifications
You can specify Viracon products, using the MASTERSPEC® Basic Section "Glass and Glazing" or the MASTERSPEC Supplemental Section "Decorative Glazing" software.

MASTERSPEC is a comprehensive and unbiased master specification system produced and distributed by the American Institute of Architects (AIA) on a licensed user basis. For further information, call 800-424-5080.

Warranty Information
Viracon's architectural products carry limited warranties. Contact our Inside Sales Department for copies of our product warranties.