{"id":73,"date":"2025-11-06T10:54:34","date_gmt":"2025-11-06T10:54:34","guid":{"rendered":"https:\/\/chemicaltempering.com\/?page_id=73"},"modified":"2025-11-14T10:40:34","modified_gmt":"2025-11-14T10:40:34","slug":"heat-tempering","status":"publish","type":"page","link":"https:\/\/chemicaltempering.com\/index.php\/heat-tempering\/","title":{"rendered":"Heat Tempering"},"content":{"rendered":"\n<h2 class=\"wp-block-heading\">Thermal Tempering Advantages and Limitations<\/h2>\n\n\n\n<p><br>Below You find normal limitations in thermal tempering.<br><\/p>\n\n\n\n<p>Lasimyynti Tammela can deliver smaller and thinner thermally tempered glasses.<br>Our minimum size is 100&#215;100 mm, instead of standard 300&#215;100 mm.<br>Minimum thickness 3 mm instead of 4 mm.<br>We can offer Heat Soak threathment which minimizes spontaneous breakage possibility.<br>(Read more in the end of this article)<\/p>\n\n\n\n<p>Thermal tempering of glass offers significant advantages in strength and safety, but it comes with specific<br>manufacturing and design limitations.<br><br><\/p>\n\n\n\n<h5 class=\"wp-block-heading\">Advantages of Thermal Tempering<\/h5>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Enhanced Strength: Thermally tempered glass is approximately four to five times stronger than<br>untreated (annealed) glass, offering greater resistance to impact, pressure, and bending loads.<\/li>\n\n\n\n<li>Improved Thermal Resistance: It can withstand rapid temperature changes and higher<br>temperatures (up to 250\u00b0C difference) that would cause regular glass to break, making it ideal for<br>oven doors, skylights, and areas with direct sunlight exposure.<\/li>\n\n\n\n<li>Safety upon Breakage: In the event of breakage, the glass shatters into small, relatively dull, cube-<br>like fragments instead of large, sharp shards. This significantly minimizes the risk of serious injury, which is why it is considered a safety glass.<\/li>\n\n\n\n<li>Scratch Resistance: The process increases the surface hardness of the glass, making it more<br>resistant to scratches and abrasion.<\/li>\n<\/ul>\n\n\n\n<h5 class=\"wp-block-heading\">Limitations of Thermal Tempering<\/h5>\n\n\n\n<ul class=\"wp-block-list\">\n<li>No Post-Production Modification: Once the glass is thermally tempered, it cannot be cut, drilled,<br>polished, or re-worked in any way. All shaping and processing must be completed before the<br>tempering process.<\/li>\n\n\n\n<li>Risk of Spontaneous Breakage: Although rare, microscopic imperfections (such as nickel sulfide<br>inclusions) within the glass can expand over time, leading to spontaneous, unpredictable breakage.<\/li>\n\n\n\n<li>Optical Distortion: The heating and rapid cooling process can cause slight surface irregularities,<br>such as minor waves or wind spots, due to contact with rollers and airflow in the tempering oven.<\/li>\n\n\n\n<li>Vulnerability at Edges and Corners: The balanced stresses within tempered glass make its edges<br>and corners the weakest points. A hard impact to these areas can cause the entire pane to shatter<br>instantly.<\/li>\n\n\n\n<li>Complete Shattering: While safer in terms of injury risk, the complete shattering of the glass upon<br>impact can pose a security risk, as it leaves an immediate, open gap in a window or door frame.<\/li>\n<\/ul>\n\n\n\n<h5 class=\"wp-block-heading\">Size and Thickness Limitations<\/h5>\n\n\n\n<p><\/p>\n\n\n\n<h6 class=\"wp-block-heading has-text-align-left\">Thickness Limitations:<\/h6>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Minimum Thickness: Glass that is too thin cannot be effectively tempered using the thermal<br>process because it lacks sufficient mass to maintain the core temperature required to create the<br>differential cooling and resulting compression. The minimum general thickness is typically 4mm.<\/li>\n\n\n\n<li>Maximum Thickness: While very thick glass can be tempered, the process becomes more difficult<br>to control consistently, which may increase the risk of optical distortions or the effectiveness of the<br>temper throughout the entire thickness. Common architectural thicknesses range up to 19mm.<br><\/li>\n<\/ul>\n\n\n\n<h6 class=\"wp-block-heading\">Size Limitations:<\/h6>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Minimum Size: There is a minimum dimension required for the glass to be handled effectively by the tempering equipment (rollers, tongs, etc.). A common minimum size is around 100mm x 300mm, although this can vary by manufacturer. Pieces that are too small may not be able to be processed thermally and would require chemical strengthening instead.<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Maximum Size: The maximum size is restricted primarily by the dimensions of the tempering<br>furnace and handling equipment. While standard &#8220;jumbo&#8221; sizes are commonly around 2.4m x 3.6m<br>(8ft x 12ft), some specialized furnaces can handle extremely large, &#8220;oversize&#8221; panes up to 3.2m x<br>16.5m for unique architectural projects.<\/li>\n<\/ul>\n\n\n\n<p>In summary, the specific size and thickness capabilities often depend on the manufacturer&#8217;s specific<br>equipment, so it is always best to consult with the glass fabricator if a project has unusual size<br>requirements.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Heat soaking<\/h2>\n\n\n\n<p><br>is a quality control process performed on fully tempered glass to minimize the risk of spontaneous<br>breakage after installation. This unexpected failure is typically caused by microscopic imperfections<br>within the glass, primarily nickel sulfide (NiS) inclusions, which are tiny, undetectable particles that can<br>expand over time.<\/p>\n\n\n\n<h5 class=\"wp-block-heading\"><br>The Process<\/h5>\n\n\n\n<p><br>After the standard thermal tempering process, the glass panels are placed in a specialized heat-soaking<br>oven and subjected to a controlled thermal cycle.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Heating Phase: The temperature inside the oven is gradually raised to approximately 290\u00b0C<br>(554\u00b0F).<\/li>\n\n\n\n<li>Holding Phase (Soaking): The glass is held at this peak temperature for a specified period,<br>typically a minimum of two to four hours.<\/li>\n\n\n\n<li>Cooling Phase: The glass is then slowly cooled to ambient temperature.<\/li>\n<\/ul>\n\n\n\n<h5 class=\"wp-block-heading\">How It Works<\/h5>\n\n\n\n<p><br>The high temperature in the oven accelerates the phase transformation and expansion of any NiS<br>inclusions present in the glass. This expansion creates sufficient internal stress to cause the defective<br>panels to shatter within the controlled environment of the oven.<br>Glass that survives the heat soak test is considered &#8220;safe&#8221; because the majority of critical NiS inclusions<br>have been forced to fail before the glass leaves the factory for installation.<br><\/p>\n\n\n\n<h5 class=\"wp-block-heading\">Purpose and Benefits<\/h5>\n\n\n\n<p><br>The main purpose of heat soaking is safety and risk mitigation:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Minimizes Spontaneous Breakage: It significantly reduces the probability of a panel breaking<br>unexpectedly after it has been installed in a building facade, skylight, or balustrade.<\/li>\n\n\n\n<li>Prevents Accidents and Costs: By identifying flawed panels in the factory, it avoids the safety<br>risks of falling glass, injury, and the high costs and inconvenience of complex, high-level<br>replacements in the field.<\/li>\n\n\n\n<li>Compliance: Many building codes and architectural specifications for critical applications (e.g.,<br>overhead glazing, structural glass) mandate the use of heat-soaked glass.<\/li>\n<\/ul>\n\n\n\n<h5 class=\"wp-block-heading\">Limitations<\/h5>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Not 100% Effective: While highly effective (reducing breakage probability significantly, such as<br>from 1 in 10,000 m2 to 1 in 1,000,000 m2), the process does not completely eliminate the risk of<br>spontaneous breakage.<\/li>\n\n\n\n<li>Added Cost and Time: The extra step of processing adds both cost and time to the glass<br>manufacturing process.<\/li>\n\n\n\n<li>No Guarantee of Quality Identification: There is no reliable method to definitively tell if an<br>installed piece of glass has been heat-soaked after the fact, other than through manufacturer<br>documentation.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>Thermal Tempering Advantages and Limitations Below You find normal limitations in thermal tempering. Lasimyynti Tammela can deliver smaller and thinner thermally tempered glasses.Our minimum size is 100&#215;100 mm, instead of standard 300&#215;100 mm.Minimum thickness 3 mm instead of 4 mm.We can offer Heat Soak threathment which minimizes spontaneous breakage possibility.(Read more in the end of&#8230;<\/p>\n","protected":false},"author":2,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_kadence_starter_templates_imported_post":false,"_kad_post_transparent":"","_kad_post_title":"","_kad_post_layout":"","_kad_post_sidebar_id":"","_kad_post_content_style":"","_kad_post_vertical_padding":"","_kad_post_feature":"","_kad_post_feature_position":"","_kad_post_header":false,"_kad_post_footer":false,"_kad_post_classname":"","footnotes":""},"class_list":["post-73","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/chemicaltempering.com\/index.php\/wp-json\/wp\/v2\/pages\/73","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/chemicaltempering.com\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/chemicaltempering.com\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/chemicaltempering.com\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/chemicaltempering.com\/index.php\/wp-json\/wp\/v2\/comments?post=73"}],"version-history":[{"count":8,"href":"https:\/\/chemicaltempering.com\/index.php\/wp-json\/wp\/v2\/pages\/73\/revisions"}],"predecessor-version":[{"id":91,"href":"https:\/\/chemicaltempering.com\/index.php\/wp-json\/wp\/v2\/pages\/73\/revisions\/91"}],"wp:attachment":[{"href":"https:\/\/chemicaltempering.com\/index.php\/wp-json\/wp\/v2\/media?parent=73"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}