BY Urmi Shah | July 05, 2023
Steam thermography is a process that is used to enhance chemical contrast in thermographic images by exposing a surface to water vapor during imaging.
The exposure of water vapor to the surface generates heat, and can differentially increase the thermographically measured apparent temperature of imaged surfaces.
Steam thermography is based on the principle of thermal imaging, which involves the detection of temperature differences on the surface of an object. When steam is directed onto a surface, it causes a temperature difference to form between the surface and the steam, which can then be detected using a thermal imaging camera.
In this technique, the steam creates a thermal gradient on the surface of the object, which can be used to reveal hidden or concealed information, such as fingerprints, blood, or alterations to a document. The steam causes a temperature difference to form between the object and the hidden information, which can then be detected using the thermal imaging camera.
The thermal imaging camera detects infrared radiation emitted by the object and converts it into a visible image. The different temperatures on the surface of the object are represented by different colors on the image, with warmer temperatures appearing as lighter colors and cooler temperatures appearing as darker colors.
Thermal imaging cameras, also known as infrared cameras or thermographic cameras, are devices that detect and capture images of the infrared radiation emitted by objects. Unlike traditional cameras that rely on visible light, thermal imaging cameras detect and measure the heat emitted by objects and translate it into a visible image.
Figure 1 - Thermal Imaging Camera
This camera consist of several components that work together to detect and capture infrared radiation emitted by objects and convert it into a visible image. The main components of a thermal imaging camera include:
• Detector: The detector is the part of the camera that detects and measures infrared radiation. It is typically made of materials such as indium antimonide or microbolometers, which are sensitive to infrared radiation and can convert it into an electrical signal.
• Optics: The optics of a thermal imaging camera consist of a lens that focuses the infrared radiation onto the detector. The lens may be made of materials such as germanium or silicon, which are transparent to infrared radiation.
• Signal processing: The electrical signal generated by the detector is processed by the camera's software to create a visible image. The software adjusts the image to account for variations in temperature across the scene, and may include features such as color palettes, temperature scales, and image enhancement tools.
• Display: The display is the part of the camera that shows the visible image created by the software. It may be a built-in screen or an external device such as a computer or smartphone.
• Housing: The housing of a thermal imaging camera is typically made of materials such as plastic or metal, and is designed to protect the camera's internal components from damage and environmental factors such as dust and moisture.
• Power source: Thermal imaging cameras require a power source to operate, which may be provided by batteries or an external power supply.
The construction of a thermal imaging camera is designed to detect and capture infrared radiation emitted by objects and convert it into a visible image that can be used for a variety of applications, from building inspections to medical diagnostics to forensic investigations
Steam thermography can be used in forensic science investigations to identify hidden or concealed evidence. The method involves using a thermal imaging camera to detect temperature differences caused by the presence of steam or moisture, which can be indicative of the presence of certain materials, substances or activities.
i. Steam thermography can be used to identify concealed drug labs, where illicit substances are manufactured. These labs often generate significant amounts of heat and steam, which can be detected by thermal imaging cameras. By using steam thermography to detect these labs, law enforcement officials can quickly and safely locate and dismantle them.
ii. Steam thermography can also be used to identify the presence of human remains in clandestine graves. The decomposition process produces heat and moisture, which can create a temperature difference that is detectable by thermal imaging cameras. By using steam thermography to locate these temperature differences, forensic investigators can pinpoint the location of the grave and recover the remains.
Thus, Steam thermography is a useful tool for forensic investigations, as it allows investigators to detect hidden or concealed evidence that may be difficult or impossible to identify through other means. By providing a non-invasive and non-destructive method for detecting temperature differences, steam thermography can help to uncover important evidence in a range of forensic contexts.
Some broad areas where steam thermography can be used:
Steam thermography can be used in forensic science investigations to detect fingerprints on non-porous surfaces, such as glass or metal.
To perform steam thermography for fingerprint detection, the object is first heated to a temperature higher than that of the steam. Steam is then directed onto the surface of the object, causing a temperature difference to form between the surface and the fingerprint. This temperature difference can then be detected using a thermal imaging camera, which will produce an image of the fingerprint as a result.
Steam thermography can be used to detect blood on a variety of surfaces, including clothing, furniture, and flooring.
The method involves using steam to create a temperature difference between the surface of the object and the blood, which can then be visualized using a thermal imaging camera.
Blood absorbs and retains heat differently than the surrounding surface, which creates a temperature difference that can be detected using a thermal imaging camera. By directing steam onto the surface of the object, the blood and surrounding surface will respond differently, and the thermal imaging camera can detect the resulting temperature difference.
Steam thermography can be used in forensic science investigations to examine questioned documents, such as checks, contracts, and legal documents. The method involves using steam to reveal alterations, erasures, or other changes made to the document that are not visible to the naked eye.
To perform steam thermography for questioned document examination, the document is exposed to steam, which can cause changes in the absorption or reflectance of ink or other materials on the surface. These changes can then be visualized using a thermal imaging camera, which will produce an image that highlights the areas of the document that have been altered or tampered with.
Steam thermography can also be used to detect the presence of additional layers or substrates in a document. By using steam to remove the uppermost layers of a document, the underlying layers or substrates can be revealed, which may contain important information or evidence.
Overall, steam thermography is a useful tool for forensic investigations, as it provides a non-destructive and highly sensitive method for detection of evidences that may be missed by other methods, which can ultimately help to solve crimes and bring perpetrators to justice.
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Note - The figures and images used in this blog are only for educational purposes.