Heat Soaked Glass

Heat Soaked Glass, also known as Heat Soaked Thermally Toughened Glass (HST), is fully tempered glass that undergoes an additional controlled heat treatment process to significantly reduce the risk of spontaneous breakage. The heat soak process involves placing tempered glass in a specialized chamber and heating it to approximately 290°C ± 10°C for a minimum of two hours. This treatment accelerates the phase transformation of nickel sulfide (NiS) inclusions within the glass – the primary cause of spontaneous breakage in tempered glass. Any glass containing problematic NiS inclusions breaks within the chamber during the heat soak process, thereby being eliminated before delivery. Heat Soaked Glass retains all the strength and safety characteristics of fully tempered glass while offering an additional layer of reliability for critical architectural applications.

Common Specifications and Parameters

Performance Characteristics

Superior Safety Performance – Heat Soaked Glass breaks into small, blunt, honeycomblike particles upon impact, minimising the risk of serious injury. The heat soak treatment ensures that nickel sulfide inclusions undergo complete phase transformation from α NiS to stable βNiS within the controlled environment, effectively eliminating the possibility of spontaneous breakage after delivery.

High Mechanical Strength – The glass is 4 to 5 times stronger than ordinary annealed glass. The thermal toughening process creates surface compression stress that must be overcome before the glass can fracture, providing exceptional resistance to impact and mechanical loads.

Excellent Thermal Stability – Heat Soaked Glass can withstand temperature differentials of 200°C or more – three times the thermal resistance of ordinary glass. This makes it highly resistant to thermal shock and suitable for applications exposed to significant temperature variations.

Enhanced Weather Resistance – The product demonstrates superior resistance to wind pressure, thermal cycling, and impact, making it ideal for demanding exterior applications.

Virtually Zero Spontaneous Breakage – Industry data indicates that heat soak treatment reduces the spontaneous breakage rate of tempered glass from approximately 3‰ to about 0.01‰.

Key Advantages

Elimination of Hidden Defects – The heat soak process serves as a destructive test that identifies and removes glass containing nickel sulfide inclusions before it leaves the factory. This proactive quality control measure prevents costly and dangerous in service failures.

Long Term Reliability – Heat Soaked Glass does not lose its bending strength characteristics or resistance to temperature differentials after the heat soak treatment. The mechanical and thermal properties remain fully intact throughout the product’s service life.

Public Safety Assurance – For buildings where glass failure could pose significant public safety risks – such as highrise facades, airports, and stadiums – Heat Soaked Glass provides an essential layer of protection against spontaneous breakage.

Reduced Maintenance and Replacement Costs – By virtually eliminating the risk of spontaneous breakage, Heat Soaked Glass reduces the need for costly post installation repairs or replacements, particularly in difficult to access locations.

Comprehensive Certification – Products can be manufactured to comply with multiple international standards including BS EN 14179-1, GB 15763.2-2009, and EN 12150-1, ensuring global acceptance and reliability.

Application Areas

Heat Soaked Glass is recommended for any architectural glazing application where safety, reliability, and longterm performance are paramount, particularly:

High Rise Building Facades and Curtain Walls – Where glass failure could result in falling debris posing serious public safety risks.

Airports and Transportation Hubs – High traffic public spaces requiring maximum safety assurance.

Stadiums and Large Public Venues – Where large glass surfaces are exposed to both high loads and public occupancy.

Commercial Building Entrances and Atriums – High visibility areas where glass integrity is critical.

Balustrades, Partitions, and Shower Screens – Applications requiring both safety glass performance and enhanced reliability.

Difficult to Access Installations – Any glass installation that would be challenging or costly to replace once construction is complete.

Skylights and Overhead Glazing – Where glass failure would pose immediate danger to people below.

How to Select Heat Soaked Glass

Determine the Required Safety Level – Assess whether the application demands the enhanced reliability of Heat Soaked Glass. For high rise buildings, public venues, and difficult to access locations, Heat Soaked Glass is strongly recommended.

Specify the Appropriate Thickness – Heat Soaked Glass is available in thicknesses from 4mm to 19mm. Selection depends on factors including wind load requirements, panel size, and structural demands.

Consider Glass Type and Optical Performance – Heat Soaked Glass can be produced in clear, low iron (ultra clear), or tinted variants depending on aesthetic and performance requirements.

Verify Standards Compliance – Ensure the product meets relevant standards such as BS EN 14179 1, GB 15763.2 2009, or EN 12150 1. For projects requiring specific certifications, confirm that the manufacturer can provide the necessary documentation.

Evaluate Manufacturer Capabilities – Choose a manufacturer with proven experience, modern production equipment, and comprehensive quality control systems. The ability to produce largeformat panels (up to 3300 × 13000 mm) may be critical for certain projects.

Assess Total Project Requirements – Consider whether the glass will be used as a monolithic panel or as part of an insulating glass unit (IGU). Heat Soaked Glass can be incorporated into various glazing configurations including laminated glass and insulating glass units.

About Shandong Yaohua Glass Co., Ltd.

Shandong Yaohua Glass Co., Ltd., located in Jinan, the capital of Shandong Province, was established in 1985. With decades of deep engagement in both domestic and international markets, the company has grown into a highly renowned and influential highend intelligent manufacturing glass processing enterprise, equipped with over 50,000 square metres of largescale modern production facilities. Leveraging advantages in brand, technology, equipment, and talent, the company has consistently achieved an annual output value of nearly RMB 400 million in recent years. It is a professional manufacturer of highend architectural glass and residential glass, a pioneer in 4SG high performance insulating glass for building facades and windows, and one of China’s major glass processing export bases.

Shandong Yaohua Glass Co., Ltd. is a National High Tech Enterprise and has received numerous prestigious honours including China Top 30 Glass Processing Enterprises, Shandong Provincial Specialised and Sophisticated Enterprise, Shandong Provincial Manufacturing Single Champion, and Shandong Provincial Technology Little Giant Enterprise.

The company has obtained ISO 9001 and ISO 45001 certifications. Its products have passed China Compulsory Certification (3C) for safety glass, China Green Building Material Certification, Australian Standard Certification, Korean KS Certification, EU CE Certification, US SGCC Certification, and North American IGCC Certification. The company places strong emphasis on independent intellectual property development and has been granted multiple national patents.

The company has made significant investments in world class production equipment. In 2022, it introduced the worldadvanced LiSEC 4SG insulating glass production line, integrated with the previously installed LiSEC glass processing system, achieving fully automated production from intelligent raw sheet warehousing to insulating glass output. In 2024, the company added two world advanced Glaston 4SG insulating glass production lines. From 2025 to 2026, the company completed the introduction and upgrade of five domestic high standard flat bent tempering furnaces, represented by the NorthGlass 8 metre doublechamber three air grid tempering furnace, along with intelligent connectivity upgrades across the entire production system.

Shandong Yaohua Glass Co., Ltd. has built its product portfolio around three fully imported 4SG high performance insulating glass production lines and five domestic high standard flat bent tempering furnaces, delivering world class quality characterised by "longlasting seal, perfectly flat and light spot free" performance. The company’s products serve customers in more than 80 countries and regions worldwide, with over 1,000 containers exported annually. Many landmark buildings around the world feature Shandong Yaohua glass, including Jinan Yaoqiang Airport (4SG), Qingdao Shangjunfu Fourth Generation Residences (4SG), Ordos Kangtai Hotel (4SG), Beijing Intellectual Property Publishing House Office Building, Qingdao Hisense Financial Center, Busan Opera House (South Korea), BMW Office Building in Gyeonggi Province (South Korea), PyeongChang Winter Olympics Venues, Bahrain NECC New Convention and Exhibition Center, and Lusaka International Airport in Zambia.

Frequently Asked Questions

Question: What is the difference between Heat Soaked Glass and regular tempered glass?

Answer: Regular tempered glass undergoes heating to approximately 650°C followed by rapid cooling to create surface compression stress. Heat Soaked Glass undergoes this same tempering process plus an additional heat soak treatment at 290°C ± 10°C for a minimum of two hours. This extra step accelerates the expansion of nickel sulfide inclusions, causing any glass with such defects to break during manufacturing rather than after installation. The result is a product with virtually zero risk of spontaneous breakage.

Question: Is Heat Soaked Glass considered safety glass?

Answer: Yes. Heat Soaked Glass is fully tempered safety glass that meets all safety glass standards. Upon breakage, it fragments into small, blunt, honeycomb like particles that minimise injury risk. It complies with safety glass standards including BS EN 12150 1 and GB 15763.2 2009.

Question: What standards apply to Heat Soaked Glass?

Answer: Heat Soaked Glass is manufactured in compliance with multiple international standards including BS EN 141791 (European Standard for heat soak process systems), GB 15763.22009 (Chinese safety glass standard), and EN 121501 (thermally toughened safety glass). The product can also be certified to meet Australian, Korean, EU, US SGCC, and North American IGCC requirements.

Question: How much does Heat Soaked Glass cost compared to regular tempered glass?

Answer: Heat Soaked Glass typically costs 15% to 20% more than regular tempered glass due to the additional heat soak treatment process and extended production time. However, this premium provides significantly enhanced reliability and virtually eliminates the risk of costly post installation spontaneous breakage.

Question: Where is Heat Soaked Glass most commonly used?

Answer: Heat Soaked Glass is most commonly specified for highrise building facades, airports, stadiums, and other public venues where glass failure could pose serious safety risks. It is also strongly recommended for difficulttoaccess installations where replacement would be costly or challenging, as well as for skylights, balustrades, and overhead glazing applications.

Question: Does Shandong Yaohua Glass Co., Ltd. produce Heat Soaked Glass?

Answer: Yes. Shandong Yaohua Glass Co., Ltd. produces heat soaked (homogenised) tempered glass in thicknesses ranging from 4mm to 19mm, with maximum flat glass dimensions of 3300 × 13000 mm and heat soak treatment available for panels up to 2500 × 6000 mm. The company’s production capabilities include multiple tempering furnaces and a dedicated homogenising (heat soak) furnace, with quality control standards compliant with GB 15763.2-2009 and internal quality standards. All products benefit from the company’s ISO 9001 certified quality management system and comprehensive international certifications.