Under normal usage, deglazing loads are generally applied parallel to the plane of the glazing material and eccentric to the sash element when it is opened, closed, or lifted out of the frame. When operating hardware is present, torsional forces may be increased. Opening and closing forces are normally applied from the interior side only. Sliding glass door panels are activated from both sides.
The ability of fenestration products to resist deglazing forces may vary with a number of factors. These factors should be considered when selecting test specimens or when interpreting test results. Bedding compounds in newly assembled sashes may not reach full strength until they have been allowed to cure for several days or weeks. Some sash materials are subject to shrinkage at low temperatures and increased elasticity at high temperatures. Therefore, a sash containing these materials may exhibit a range of deglazing resistance due to varying temperature conditions. Normal manufacturing tolerances and clearances in sash members and glazing materials may also affect deglazing resistance. Further, although fenestration products are designed to operate within certain force limits, improper installation, wear, and abuse may increase the forces necessary for sash operation.
When determining which members of a given sash shall be tested for deglazing resistance, consideration must be given to the manner in which the sash may be operated when normally installed. Handles and lift devices are usually located on the sash for the convenience of the operator and therefore dictate the normal direction of operation.
Test Method A presents a technique for actual measurement of the deglazing forces of an individual sash member.
Test Method B presents a technique for measuring the deglazing force of two opposite members. This test method is intended for quality control measurements.
