{"id":32172,"date":"2024-07-18T17:31:18","date_gmt":"2024-07-18T16:31:18","guid":{"rendered":"https:\/\/www.hawkins.biz\/?post_type=insight&#038;p=32172"},"modified":"2025-07-29T17:09:11","modified_gmt":"2025-07-29T16:09:11","slug":"materials-science-fire-investigation","status":"publish","type":"insight","link":"https:\/\/www.hawkins.biz\/insight\/materials-science-fire-investigation\/","title":{"rendered":"The Role of Materials Science in Fire Investigations"},"content":{"rendered":"\t\t<div data-elementor-type=\"wp-post\" data-elementor-id=\"32172\" class=\"elementor elementor-32172\" data-elementor-post-type=\"insight\">\n\t\t\t\t\t\t<section class=\"has_eae_slider elementor-section elementor-top-section elementor-element elementor-element-7b40214 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-eae-slider=\"63033\" data-id=\"7b40214\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-71bebd1\" data-eae-slider=\"18839\" data-id=\"71bebd1\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-d1559da elementor-widget elementor-widget-text-editor\" data-id=\"d1559da\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>Investigations to identify both the origin and cause of fires form a large portion of Hawkins\u2019 cases. An experienced fire investigator will make their initial observations at the fire scene to identify where the damage is most severe, whether there are anomalies in the damage and debris, and whether a source of the ignition can be identified.\u00a0\u00a0<\/p><p>The heat of the fire causes damage to different <a href=\"https:\/\/www.hawkins.biz\/expertise\/materials-chemistry-biology\/\" target=\"_blank\" rel=\"noopener\">materials<\/a> in different ways. Organic materials such as wood and paper can be completely consumed to ash, and plastics may be melted and burnt to almost unrecognisable residues. However, a fire will not always cause complete destruction. Following the patterns of burnt and unburnt wood damage, or where plastics or paint coatings have either charred, softened, or melted, can help track the fire spread and identify where the most damage occurred, which is often where the fire started.<\/p><h4><span style=\"color: #007aa3;\">Broken Glass<\/span><\/h4><p>Glass windows will not usually reach temperatures hot enough to melt in a fire, but broken windows are often present at fire scenes, not least because the heat of a fire can crack glass panels due to thermal stress. Broken windows can be a result of someone breaking in to deliberately set a fire or may have been broken by the fire service to gain access or to assist with clearing smoke from the building. A fire investigator needs to recognise glass fracture patterns consistent with a thermally cracked window, differentiating them from those that have been deliberately broken, as this can have significant consequences for the potential recovery or repudiation of a claim. Cracks from heat damage initiate from the edge of a window and propagate around the glass panel in a gently curving shape. In contrast, a glass window that has been hit or struck will show an impact mark with cracks propagating radially from the point of impact where the glass may be crushed.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"has_eae_slider elementor-section elementor-top-section elementor-element elementor-element-755715f elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-eae-slider=\"36661\" data-id=\"755715f\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-86e681d\" data-eae-slider=\"20002\" data-id=\"86e681d\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<section class=\"has_eae_slider elementor-section elementor-inner-section elementor-element elementor-element-11c9174 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-eae-slider=\"23824\" data-id=\"11c9174\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-50 elementor-inner-column elementor-element elementor-element-a630250\" data-eae-slider=\"92276\" data-id=\"a630250\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-9ff70d4 elementor-widget elementor-widget-image\" data-id=\"9ff70d4\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img fetchpriority=\"high\" decoding=\"async\" width=\"800\" height=\"732\" src=\"https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-1.jpg\" class=\"attachment-large size-large wp-image-32186\" alt=\"Heat-damaged window from a previous Hawkins investigation\" srcset=\"https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-1.jpg 899w, https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-1-300x275.jpg 300w, https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-1-768x703.jpg 768w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-50 elementor-inner-column elementor-element elementor-element-414b6e7\" data-eae-slider=\"32421\" data-id=\"414b6e7\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-231e99f elementor-widget elementor-widget-image\" data-id=\"231e99f\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"342\" height=\"823\" src=\"https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-2.jpg\" class=\"attachment-large size-large wp-image-32187\" alt=\"Impact damaged glass panel from a previous Hawkins case\" srcset=\"https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-2.jpg 342w, https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-2-125x300.jpg 125w\" sizes=\"(max-width: 342px) 100vw, 342px\" \/>\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"has_eae_slider elementor-section elementor-top-section elementor-element elementor-element-e78eacb elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-eae-slider=\"49360\" data-id=\"e78eacb\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-3d141e0\" data-eae-slider=\"63653\" data-id=\"3d141e0\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-535aa75 elementor-widget elementor-widget-text-editor\" data-id=\"535aa75\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p><em>Heat-damaged windows (left) and impact damage to a glass door panel indicated with an arrow (right).<\/em><\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"has_eae_slider elementor-section elementor-top-section elementor-element elementor-element-be30725 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-eae-slider=\"55253\" data-id=\"be30725\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-ee94b92\" data-eae-slider=\"27112\" data-id=\"ee94b92\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-b12c329 elementor-widget elementor-widget-text-editor\" data-id=\"b12c329\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p><span style=\"color: #000000;\">In addition to recognising the cracking patterns, investigators will also examine any glass fragments that have fallen from the window. Identifying if the fragments are soot-stained, and whether the glass has fallen inside or outside the window, will determine when and how the window was broken.\u00a0<\/span><\/p><h4>Fire Damage to Structural Steel<\/h4><p><span style=\"color: #000000;\">After large fires, the majority of identifiable materials that remain are metals, because they do not burn in fires, but they may melt or soften. A typical domestic or vehicle fire can reach temperatures in excess of 900\u00b0C. The fire is unlikely to get hot enough to melt iron and steel (above 1500\u00b0C), but even metals that don\u2019t melt will nonetheless be affected by the heat of a fire, as the yield strength of metals and alloys reduces at higher temperatures. The strength of steel can be reduced by half when it is heated above 500\u00b0C. This means that steel beams can bend, distort, and buckle, and can cause the collapse of a roof structure under the heat of a fire. This presents a significant risk because the temperature will be highest at the roof level in an enclosed building fire.<\/span><\/p><p>\u00a0<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"has_eae_slider elementor-section elementor-top-section elementor-element elementor-element-3da3b86 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-eae-slider=\"70380\" data-id=\"3da3b86\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-816be6e\" data-eae-slider=\"96116\" data-id=\"816be6e\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-561d333 elementor-widget elementor-widget-image\" data-id=\"561d333\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img decoding=\"async\" width=\"800\" height=\"821\" src=\"https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-3.jpg\" class=\"attachment-large size-large wp-image-32188\" alt=\"Image of a structural collapse of a steel framed roof caused by fire\" srcset=\"https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-3.jpg 949w, https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-3-292x300.jpg 292w, https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-3-768x788.jpg 768w\" sizes=\"(max-width: 800px) 100vw, 800px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Structural collapse of a steel framed roof as a consequence of a fire.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"has_eae_slider elementor-section elementor-top-section elementor-element elementor-element-e0b22c4 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-eae-slider=\"55954\" data-id=\"e0b22c4\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-e1baad6\" data-eae-slider=\"48250\" data-id=\"e1baad6\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-88ac45c elementor-widget elementor-widget-text-editor\" data-id=\"88ac45c\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>When steels are heated above 723\u00b0C they go through what is known as a \u2018phase change\u2019 and the microscopic crystalline structure of the solid steel (i.e. its microstructure) changes. When it cools back down again, a steel that has been through a phase change usually ends up with a different set of room temperature properties; i.e. after a phase change the steel has been permanently altered by the heat of the fire. In contrast, steel that has been exposed to a heat lower than 723\u00b0C retains the same microstructure once it cools down, and therefore returns to its original room temperature strength. Whether a steel beam or component has been permanently affected by the heat of a fire can have implications for the insurance claim value and the possible repair options. By looking at the microstructure of the steel, it is possible to determine whether steel has been fundamentally damaged by the fire.<\/p><p>To reveal a metal\u2019s microstructure, the metal sample\u2019s surface is first polished to a mirror finish. This is done by grinding, using increasingly finer grades of sandpaper and then polishing with diamond polishing paste. The polished surface is then etched with an acid, which eats away at the boundaries around the crystalline grains in the metal microstructure. The etched surface can then be examined using a microscope to reveal the microstructure, i.e. the size, shape, and arrangement of the crystals of different constituent phases of the metal. For metal components in service, the microstructure can be captured using the local preparation of a small polished and etched surface, and then laying a softened sheet of thin acetate over the surface which embeds into the etched grain boundaries. A replica of the microstructure is captured on the acetate sheet, which can then be taken from the site for a microscopic examination at a laboratory. Comparing the microstructures from undamaged areas to those that have been in the fire, can show whether a steel has been heated sufficiently to be permanently affected, or whether it remains structurally sound.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"has_eae_slider elementor-section elementor-top-section elementor-element elementor-element-fbf1461 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-eae-slider=\"96048\" data-id=\"fbf1461\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-881e9e0\" data-eae-slider=\"96388\" data-id=\"881e9e0\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-dfbd4f0 elementor-widget elementor-widget-image\" data-id=\"dfbd4f0\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"707\" height=\"660\" src=\"https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-4.jpg\" class=\"attachment-large size-large wp-image-32189\" alt=\"Image of materials expert Philippa Moore sampling the microstructure of a fire-blackened steel beam\" srcset=\"https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-4.jpg 707w, https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-4-300x280.jpg 300w\" sizes=\"(max-width: 707px) 100vw, 707px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">On-site metallographic preparation to sample the microstructure of a fire-blackened steel beam.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"has_eae_slider elementor-section elementor-top-section elementor-element elementor-element-ea32358 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-eae-slider=\"29819\" data-id=\"ea32358\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-88ddf74\" data-eae-slider=\"78733\" data-id=\"88ddf74\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-8d804e8 elementor-widget elementor-widget-text-editor\" data-id=\"8d804e8\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h4><span style=\"color: #007aa3;\">Other Metals and Alloys<\/span><\/h4><p>In addition to steel, there can be many different metals and alloys present in a fire scene. Understanding of the thermal behaviour of various common metals and alloys, such as those shown in the melting temperature given in Table 1, can help to understand the temperatures that have been reached in a fire. While it may not be immediately obvious what a particular metal is, some techniques can help identify metals in the debris of a fire scene.<\/p><p>A magnet will stick to mild steel, structural steel and cast iron, but not to austenitic stainless steel, aluminium or copper alloys. Looking at the colour of the metal.; dull grey metals could be iron, steel or lead; brighter grey is typical of aluminium or zinc-galvanised steel; the orange colour of copper is characteristic; as is the yellow-golden colour of some brasses.<\/p><p>The acidic constituents of smoke, combined with the water from extinguishing a fire, can cause many metal surfaces to corrode after a fire. The colour of the corrosion products can also help identify a metal. Orange coloured rust is characteristic of iron and steel, while blue\/green coloured corrosion occurs with copper. A white oxide could mean lead is present. <\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"has_eae_slider elementor-section elementor-top-section elementor-element elementor-element-d4d5ab2 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-eae-slider=\"59884\" data-id=\"d4d5ab2\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-618cb84\" data-eae-slider=\"99425\" data-id=\"618cb84\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-687d9ff elementor-widget elementor-widget-image\" data-id=\"687d9ff\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"395\" height=\"196\" src=\"https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/table.jpg\" class=\"attachment-large size-large wp-image-32176\" alt=\"A table to show the melting temperatures of various common metals and alloys\" srcset=\"https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/table.jpg 395w, https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/table-300x149.jpg 300w\" sizes=\"(max-width: 395px) 100vw, 395px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Table 1\tMelting temperatures of various common metals and alloys.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"has_eae_slider elementor-section elementor-top-section elementor-element elementor-element-4a535a8 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-eae-slider=\"89186\" data-id=\"4a535a8\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-b721951\" data-eae-slider=\"66395\" data-id=\"b721951\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-21e8a66 elementor-widget elementor-widget-text-editor\" data-id=\"21e8a66\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<h4><span style=\"color: #007aa3;\">Metal Behaviour in a Fire<\/span><\/h4><p>Two particular <a href=\"https:\/\/www.hawkins.biz\/expertise\/materials-chemistry-biology\/metallurgy\/\" target=\"_blank\" rel=\"noopener\">metallurgical<\/a> features to look out for in fire scenes are <em>arc strikes<\/em> and <em>contact alloying<\/em>.<\/p><p>An arc is a single-event electrical discharge across conductors, often copper wires. The localised heat from the arc is enough to melt the copper at the arc contact point. An arc will often leave a notch or groove where molten material is transferred between conductors. Finding evidence of an electrical arc is significant because a spontaneous arc strike from a faulty or damaged electrical item could provide sufficient heat to ignite a fire. However, arcs can occur as both a consequence and the cause of a fire. The heat from an established fire melts or burns the insulation from energised cable or flex, which then allows arc strikes to occur.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"has_eae_slider elementor-section elementor-top-section elementor-element elementor-element-6b66185 elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-eae-slider=\"46105\" data-id=\"6b66185\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-bda8963\" data-eae-slider=\"89017\" data-id=\"bda8963\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-8354f6d elementor-widget elementor-widget-image\" data-id=\"8354f6d\" data-element_type=\"widget\" data-widget_type=\"image.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t\t\t\t<figure class=\"wp-caption\">\n\t\t\t\t\t\t\t\t\t\t<img loading=\"lazy\" decoding=\"async\" width=\"350\" height=\"263\" src=\"https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-5.png\" class=\"attachment-large size-large wp-image-32190\" alt=\"The image depicts high-magnification of two ends of copper wires after an arc strike between them, showing characteristic notch and melted droplet from a previous Hawkins case\" srcset=\"https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-5.png 350w, https:\/\/www.hawkins.biz\/wp-content\/uploads\/2024\/07\/PM-pic-5-300x225.png 300w\" sizes=\"(max-width: 350px) 100vw, 350px\" \/>\t\t\t\t\t\t\t\t\t\t\t<figcaption class=\"widget-image-caption wp-caption-text\">Figure 4\tHigh magnification image of the appearance of two ends of copper wires after an arc strike between them, showing characteristic notch and melted droplet.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<section class=\"has_eae_slider elementor-section elementor-top-section elementor-element elementor-element-d7ee8cb elementor-section-boxed elementor-section-height-default elementor-section-height-default\" data-eae-slider=\"96227\" data-id=\"d7ee8cb\" data-element_type=\"section\">\n\t\t\t\t\t\t<div class=\"elementor-container elementor-column-gap-default\">\n\t\t\t\t\t<div class=\"has_eae_slider elementor-column elementor-col-100 elementor-top-column elementor-element elementor-element-6516d57\" data-eae-slider=\"76571\" data-id=\"6516d57\" data-element_type=\"column\">\n\t\t\t<div class=\"elementor-widget-wrap elementor-element-populated\">\n\t\t\t\t\t\t<div class=\"elementor-element elementor-element-c56814d elementor-widget elementor-widget-text-editor\" data-id=\"c56814d\" data-element_type=\"widget\" data-widget_type=\"text-editor.default\">\n\t\t\t\t<div class=\"elementor-widget-container\">\n\t\t\t\t\t\t\t\t\t<p>Fire investigators interpret the location and patterns of arc strikes, together with other fire damage or melting around the arc site, as part of the evidence they use to build up their impression of what caused the fire. Identifying arc strikes in wires and conductors can help track fire progression, in a process known as arc mapping. Between two wires, for instance, the furthest arc from the electrical supply must have been the first one to occur. This is because if an arc occurred closer to the electrical power supply first, that would prevent the current from travelling further down the wires. The sequence of various arc strike events can be mapped in this way.<\/p><p>Contact alloying, also known as <em>eutectic melting<\/em> can occur when molten metal drops onto a solid component of a different metal. Often the initial liquid metal is aluminium, which can be present in sufficient amounts in some fire scenes that when it melts above 600\u00b0C it can trickle and drip.<\/p><p>An alloy is a mixture of two (or more) different metallic elements. An effect of this is that the alloy can have different properties to either of the individual constituents; an example is that yellow brasses behave differently to pure copper or pure zinc, its two constituent elements. When liquid aluminium drips onto solid copper, for instance, the interface between them forms a thin layer of aluminium-copper alloy. At certain proportions of aluminium to copper, these alloys can have melting points lower than pure aluminium. At a specific composition, called the <em>eutectic composition<\/em>, the melting point will be at its lowest. In the aluminium-copper example, the eutectic has 35% copper and 65% aluminium and melts at only 542\u00b0C. Therefore, liquid aluminium at 600\u00b0C dripping onto solid copper, can form a liquid alloy, with the copper appearing to <em>\u2018melt away\u2019<\/em>; hence the term<em> \u2018eutectic melting\u2019<\/em>. Without understanding how contact alloying can occur, the risk is that the discovery of melted copper at a fire scene might lead to an assumption that temperatures had exceeded 1000\u00b0C, or that there was an arc-strike to the copper, potentially misleading the investigator in their interpretation of the fire damage.<\/p><p>When molten liquid metals that have re-solidified in an unusual manner are found in fire debris, they can be identified by further laboratory work, including metallography to identify the microstructures and mixing in the alloy, and chemical analysis to determine the elements present.<\/p><h4><span style=\"color: #007aa3;\">Summary<\/span><\/h4><p>An understanding of the general behaviours of metals, plastics and glass when exposed to fire is a necessary part of a fire investigator\u2019s experience. Consulting with a forensic materials engineer when further analysis is needed can help get to the root cause of the fire, identify if there are prospects for recovery or repudiation and help scope the size of a claim relating to damaged steelwork that might appear smoke-blackened, but is fundamentally undamaged.<\/p><h4><span style=\"color: #007aa3;\">About the Author<\/span><\/h4><p>Materials expert <a href=\"https:\/\/www.hawkins.biz\/experts\/philippa-moore\/\" target=\"_blank\" rel=\"noopener\">Dr Philippa Moore<\/a> specialises in materials failures, escape of water and oil, and mechanical and engineering failures. Philippa graduated from the University of Cambridge with MA and MSci degrees in materials science and metallurgy. She then spent 18 years working at TWI Ltd and developed an international reputation in fracture toughness testing, and engineering failure investigations, often of welded steel structures, through her project work and consultancy. Philippa previously led forensic investigations of metallic and\/or non-metallic components that had cracked, fractured, or failed, and is an expert on topics related to welding engineering, materials science &amp; metallurgy, failure modes in metals, and structural integrity.<\/p><p>With extensive experience in forensic investigations, Philippa has published over 45 conference and journal papers on her academic research, and on topics supporting her involvement on British and International standards committees for fracture testing.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t<\/div>\n\t\t","protected":false},"excerpt":{"rendered":"<p>Fire causes damage to materials in different ways. Patterns can help track the fire spread identifying where most damage occurred, which is where the fire started.  <\/p>\n","protected":false},"featured_media":32239,"parent":0,"template":"","insight_category":[],"experties":[66,68],"class_list":["post-32172","insight","type-insight","status-publish","has-post-thumbnail","hentry","experties-fire-explosions","experties-materials-chemistry-biology"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO plugin v25.5 - https:\/\/yoast.com\/wordpress\/plugins\/seo\/ -->\n<title>Fire Forensics: Role of Materials Science<\/title>\n<meta name=\"description\" content=\"Explore how materials science helps forensic experts identify fire origins and causes by analyzing damage patterns in various materials.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.hawkins.biz\/insight\/materials-science-fire-investigation\/\" 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