Since 2002, Manko Window Systems has been producing heat-treated glass for projects across the Midwest. All three of Manko’s manufacturing locations are equipped with at least one tempering furnace. Since 2015, Manko has invested in four state-of-the-art Glaston FC500 furnaces to add to its current equipment. These furnaces not only give Manko the opportunity to increase capacity and throughput, but can provide the highest quality of glass to meet the Skyline Spec (upon request).
The heat-treatment process all begins by cleaning up the outside edges of the annealed glass. If the glass is fabricated with a clean edge already, it will bypass the seaming table, however if not, it will need to have the edges seamed. This process helps eliminate unequal temperatures around the edge of the glass while in the furnace (to help reduce glass breakage). After the seaming table, the glass moves to the washer, which cleans and removes any particles on the surface of the glass. It is then automatically moved to the furnace. In the furnace, the glass is heated to approximately 1,200° F for a specific period of time depending on the thickness, color, and properties of the glass. Immediately after the glass leaves the furnace it moves to the quench. The quench rapidly forces air onto both surfaces of the glass, cooling it quickly. This process puts the surface of the glass in a state of high compression and the central core in tension. The tension (core) area makes up the middle 60% of the thickness of the glass. The compression area encompasses the remaining 20% of the outer edges of the glass (see diagram below). It is in the quench where the end product becomes either fully tempered or heat-strengthened glass, depending on the amount of cool air forced onto the glass.
- Fully tempered glass is typically four times stronger than annealed glass of the same properties and can qualify as safety glazing. When broken, fully tempered glass breaks into small pieces, reducing the opportunity for serious cutting or piercing injuries.In order for the product to meet safety glazing, the ten largest particles taken from a broken fully tempered lite of glass must weigh no more than the equivalent weight of 10 sq. in. of the original glass.Fully tempered glass is required to have either a minimum surfacecompression of 10,000 psi or an edge compression of not less than 9,700 psi.
- Heat-strengthened glass is typically two times stronger than annealed glass of the same properties. The break pattern of heat-strengthened glass varies by size and shape depending on the amount of surface and edge compression. The larger the compression psi is, the smaller the break particles are.By requirement, the surface compression of heat-strengthened glass is between 3,500 psi and 7,500 psi, however it does not meet safety glazing requirements.
- ASTM C 1048 –Standard Specification for Heat-Treated Flat Glass – Kind HS, Kind FT Coated and Uncoated Glass
- ANSI Z97.1 –American National Standard for Safety Glazing Materials Used in Buildings – Safety Performance Specifications Method of Test
- CPSC 16 CFR 1201 –Safety Standard for Architectural Glazing Materials