O T H E R T O O L S F O R I N V E S T I G AT I O N AND MONITORING OTHER TOOLS FOR INVESTIGATION AND MONITORING ILLUSTRATED EXAMPLES 103 T 104 ILLUSTRATED EXAMPLES OTHER TOOLS FOR INVESTIGATION AND MONITORING Overview of Diagnostic Indirect Tools for Conservation John A. Fidler Tools and techniques for the surveying, recording, attempts to defi ne and explain the types of tools features, deforming or moving components and documentation of historic places are part of a available and place them in a conservation context, and providing indications about their Tdiverse and complicated fi eld. When applied in the prior to describing their function and use in more condition and performance in time. service of conservation rather than for academic detail. Some tools, such as tape measures, levels, and total research purposes or as part of an archaeological In conservation, there are two distinct areas of station theodolites, involve direct handheld or investigation, the application of the equipment and survey and recording, with a degree of overlap hand-eye relationships with the operator that are methods to achieve specifi c conservation-related between them: generally simpler to understand and use and are outputs becomes particular and essential, driven by cheaper to operate than indirect tools. Indirect the needs of the architects, engineers, and conser- 1. Metric surveying and recording. This technology such as radiography or thermography— vators involved in the conservation process. area is used to establish the quantifi able often from the medical, aviation, or military physical disposition of form and space. Base Too often the dialogue between surveyors and arena—requires specialized operators and software documentation can be employed in subse- conservators becomes mired in the technical as well as expensive equipment whose documenta- quent complementary phases of a conserva- language of their respective professions—language tion needs to be interpreted for the conservation tion project to map historical, technical, and that neither party fully understands—often leading team to benefi t from the data. Although many other data for assessment, analysis, and to differing expectations. When conservation pieces of equipment and their associated software synthesis of information to create a plan, professionals do not have the option of delegating are being simplifi ed by their manufacturers to the then inform, guide, and instruct others in surveying, recording, and documentation to others, “point-and-shoot” kind of format of, say, a digital taking conservation action. or wish to deliver these components themselves, camera, they remain expensive items usually the integration of actions is often more successful. 2. Diagnostic surveying and recording. contracted temporarily or deployed as part of a The problem comes with larger, more complicated This area is used to locate, isolate, assess, or subcontractor’s hardware. The following is an projects in which specialist equipment, software monitor physical phenomena affecting the overview of the diagnostic indirect tools available and data manipulation, and other complexities are heritage asset. Additional documentation can for conservation. required for cost-effective delivery. This section overlay base documentation and further inform the conservation project’s develop- ment in relation to buried or concealed OVERVIEW OF DIAGNOSTIC TOOLS ILLUSTRATED EXAMPLES 105 Water Optical and Digital Endoscopy The term laser is an acronym for light amplification possible to “see” variations in temperature caused by stimulated emission of radiation. Lasers emit by different materials, voids, and other changes of The simplest way to describe endoscopy is to use light in a narrow, well-defined beam within a construction. the analogy of a periscope: it enables operators to coherent set of wavelengths, and over short dis- look through a long, rigid, or flexible tube inside tances are extremely straight. Used horizontally, Radiography the fabric of a building through holes as small as lasers can be used to align features, determine 4–5 millimeters in diameter. Until the recent Shorter energy wavelengths are necessary to disposition or deflection, and measure angles. A development of tiny digital cameras with motorized deploy radiographic imaging to “see” concealed simpler, cheaper tool is the water line level, which focusing, endoscopy used light-guide bundles of objects within the historic fabric and record it on consists of a flexible, small-diameter plastic or fiber-optic cables to transmit light into cavities, film. X-ray radiography in the range of 15–33 rubber hose pipe with open ends to which plastic collect received light, and pass images back to the kilovolts can be used to find and assess the condi- or glass ends are added. The hose is filled with eye. With range-finding optics, the equipment can tion of timber framing under plasterwork, or of water and the two ends moved up or down, even be used to determine the location or dimensions of floor construction without lifting carpets. Linear around corners, and the horizontal level is deter- cavities or objects, assess the condition of con- accelerator (LINAC) radiography and gamma mined by equalization of atmospheric pressure. cealed pipes or fixings, or aid the routing of wiring radiography have also been employed in the within composite construction. megavoltage range to locate and quantify steel Oblique Angle and Color Filter Photography reinforcement in bridge decks or corroding buried Water, Plumb, and Laser Leveling A simple method of finding concealed doorways or wrought iron in the stonework of lighthouses and window reveals under plastered or stuccoed walls country houses. To assess the trueness, level and relative levels, and is to use oblique angle or color filter photography. plumb or vertical nature of an element of construc- Oblique angle photography captures subtle shadow Magnetometry tion—for example, subsiding floors, leaning walls, lines of inconsistencies and changes of plane in or sagging beams—a variety of levels can be Magnetometer surveys are a type of geophysical plaster surfaces. Color filter, or colored light, employed for repeatable measurements. The mapping technique that relies on the stability of the photography captures partial and different reflec- simplest and one of the oldest construction tools is world’s relatively static magnetic field. These tances in surfaces and helps to reveal patches and the plumb bob. A heavy weight is suspended on the surveys can detect anomalies caused by cultural changes in surface under coatings. end of a long string or wire, which is hung verti- objects interfering with that magnetic field. They cally from the top of a structure. The base of this can be used to locate long-forgotten conduit Infrared Photography and Thermography pendulum is then suspended in water or oil to systems, as well as pipes, cables, or remains buried minimize movement. The vertical line can be Infrared film photography is being superseded by in the ground. measured at fixed points against the structure to thermography or thermal imaging, a type of Metal detectors are employed for pachymetry (e.g., determine the lean of the wall. Laser plumb bobs infrared imaging used to discern concealed open- thickness) measurement in masonry structures by are used in the same way. ings and other anomalies under the surfaces of utilizing electromagnetic induction to detect under- historic facades and internal paneled walls. lying metalwork. They are used especially in the Thermographic cameras detect radiation in the construction industry to detect and size steel infrared range of the electromagnetic spectrum reinforcing bars buried in concrete, as well as pipes (roughly 900–14,000 nanometers, or 0.9–14 µm) and wires buried in walls and floors. In its simplest and produce images of that radiation. Because form, a metal detector consists of an oscillator, infrared radiation is emitted by all objects based on which generates a current that passes through a their surface temperatures, thermography makes it coil, producing an alternating magnetic field. If a 106 ILLUSTRATED EXAMPLES OTHER TOOLS FOR INVESTIGATION AND MONITORING piece of metal, which is electrically conductive, is Pulse Radar Stress-wave Transmission (impact-echo) close to the coil, eddy currents will be induced in Radar is an acronym for radio detection and Using transducer technology, surface and subsur- the metal; this in turn produces an alternating ranging. When fired at the ground or at a thick face vibrations in structures can be detected and magnetic field of its own. If another coil is used to masonry structure, long-wave radiation is partly used to determine anomalies, voids, and other measure the magnetic field (acting as a magnetom- reflected at the surface, partly absorbed, and partly construction problems in otherwise homogeneous eter), the change in the magnetic field due to the transmitted through the construction. Reflections construction. First, the heads of the transducer are metallic object can then be detected. and echoes from this energy are transmitted back placed on either side of a masonry column, for to the receiving antennae, and the time delays in example, or along the side of a historic railway’s Ultrasound Pulse Transmission transmission and losses in signal strength are viaduct. The structure is then hit or impacted with Ultrasound surveys and testing, or sonography, compared to those in the original signal to reveal a known