Moisture meters are measuring instruments used to measure the percentage of water in a given substance, as physical properties are strongly affected by moisture content and high moisture content for a period of time may progressively degrade a material. Meters exist for various substances, including wood, building materials, concrete, and soil.
Moisture meters are measuring instruments used to measure the percentage of water in a given substance. Direct gravimetric measurement of free moisture requires removing, drying, and weighing of a sample, so moisture sensors measure the volumetric water content indirectly by using some other property of the substrate, such as electrical resistance or dielectric constant.
Moisture content can be used to determine if the material is ready for use, unexpectedly wet or dry, or otherwise in need of further inspection. Wood and paper products are very sensitive to their moisture content. Physical properties are strongly affected by moisture content and high moisture content for a period of time may progressively degrade a material.
Newly-cut logs can have a moisture content (MC) of 80% or more, depending on species. Since wood shrinks, and can also split, twist or otherwise change shape as it dries, most wood is dried before being used. This is most often done using a kiln, but may use the air drying method, which is much slower. In most parts of the United States, the minimum moisture content that can be generally obtained in air drying is about 12 to 15 percent. Most air-dried material is usually closer to 20 percent moisture content when used. [1]
In-kiln drying is usually monitored by some type of moisture meter. Moisture meters are used to measure the amount of water in the wood so that the woodworker can determine if it is suitable for the intended purpose. Building inspectors and many more, carpenters, hobbyists, and other woodworkers often are required to have moisture meters. Wood flooring installers, for example, have to verify that the MC of the wood matches the relative humidity in the air of the building. If this step is skipped, a vast array of problems may present itself: cracking, cupping, crowning, buckling, sunken joints, and cracked finishes.
The problems caused by varying degrees of moisture content in wood go beyond simple shrinkage in the dimensions of wood parts. Problems with distortions in the shape of the wood, such as twisting, warping and cupping, occur because of the difference in the degree of dimensional change in wood cells tangentially (perpendicular to the grain and parallel to the growth rings) versus radially (perpendicular to the growth rings). [2]
A moisture meter gives a reading of the approximate moisture content of wood. The reading helps in determining whether the wood is suitably dry for its intended purpose. The moisture content reading can also assist in planning a project design that will accommodate future changes in dimension caused by changes in relative humidity. The amount of overall shrinkage lumber will undergo in the drying process varies from wood species to wood species. The difference between radial and tangential shrinkage also varies from species to species. Woods with a low ratio of tangential to radial shrinkage, such as teak and mahogany, are less prone to distortion due to changes in moisture content than woods with a high ratio, such as eastern white pine and certain species of oak. Species with both low overall shrinkage and a low tangential/radial shrinkage ratio are more stable and will react better to changes in moisture content. [3]
For wood that is to be used in making furniture, for wood floors, in construction or for any building project, the ideal state is one of equilibrium moisture content (EMC). EMC means that the wood is in balance with the relative humidity it surrounding environment, and is therefore neither gaining or losing in moisture content. In reality, however, it is extremely rare for an environment to maintain a constant fixed relative humidity, and some degree of dimensional change along with seasonal changes in relative humidity is to be expected. [4]
For typical woodworking operations, two basic types of moisture meters are available. [5] Depending in the brand, pin-type meters measure the electrical resistance, termed resistivity, or its reciprocal, conductance, of the wood substrate. [6] Water freely conducts electricity; consequently, increasing water content correlates to increased conductance. Pin-type meters incorporate two pin electrodes which are driven into the wood fibers and directly measure electrical resistance or conductivity. Each brand of moisture meter utilizes proprietary calculations and displays the final moisture content as a percentage.
The second type of moisture meter relies on the dielectric properties of wood. The meter incorporates two pads which serve as rubber electrodes that transmit and receive a signal when pressed into the wood substrate. The pad type moisture meter is non-invasive in nature and requires only surface contact with the wood to obtain a reading. [7] [8] The non-invasive meter creates a low-frequency electrical wave between the two pads and measures the electrical properties of the wood, similar to the invasive pin-type meter. [9]
Moisture meters may also be utilized by building-industry professionals and water damage restoration consultants to ascertain precise moisture content of a wide range of materials found in the built environment, such as gypsum board drywall or interior finish plaster. Locating high moisture within buildings is essential in locating leaks that may not be visible to the eye. [10] Moisture content is measured in the same manner as wood and displayed in Wood Moisture Equivalent, or WME. WME is the theoretical moisture content that the substrate would contain if it were wood. This ability to locate and measure moisture anomalies can help manage and control indoor air quality by locating and preventing hidden mold growth within buildings. [11]
Joinery is a part of woodworking that involves joining pieces of wood, engineered lumber, or synthetic substitutes, to produce more complex items. Some woodworking joints employ mechanical fasteners, bindings, or adhesives, while others use only wood elements.
Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance's molecules, adsorbing substances can become physically changed, e.g. changing in volume, boiling point, viscosity or some other physical characteristic or property of the substance. For example, a finely dispersed hygroscopic powder, such as a salt, may become clumpy over time due to collection of moisture from the surrounding environment.
A hygrometer is an instrument which measures the humidity of air or some other gas: that is, how much water vapor it contains. Humidity measurement instruments usually rely on measurements of some other quantities such as temperature, pressure, mass and mechanical or electrical changes in a substance as moisture is absorbed. By calibration and calculation, these measured quantities can lead to a measurement of humidity. Modern electronic devices use the temperature of condensation, or they sense changes in electrical capacitance or resistance to measure humidity differences. A crude hygrometer was invented by Leonardo da Vinci in 1480. Major leaps came forward during the 1600s; Francesco Folli invented a more practical version of the device, while Robert Hooke improved a number of meteorological devices including the hygrometer. A more modern version was created by Swiss polymath Johann Heinrich Lambert in 1755. Later, in the year 1783, Swiss physicist and Geologist Horace Bénédict de Saussure invented the first hygrometer using human hair to measure humidity.
A humidor is a humidity-controlled box or room used primarily for storing cigars, cigarettes, cannabis, or pipe tobacco. Either too much or too little humidity can be harmful to tobacco products; a humidor's primary function is to maintain a steady, desirable moisture level inside; secondarily it protects its contents from physical damage and deterioration from sunlight. For private use, small wooden boxes holding a few dozen or fewer cigars are common, while cigar shops may have walk-in humidors. Many humidors use hygrometers to monitor their humidity levels.
A log house, or log building, is a structure built with horizontal logs interlocked at the corners by notching. Logs may be round, squared or hewn to other shapes, either handcrafted or milled. The term "log cabin" generally refers to a smaller, more rustic log house, such as a hunting cabin in the woods, that may or may not have electricity or plumbing.
A humidifier is a household appliance or device designed to increase the moisture level in the air within a room or an enclosed space. It achieves this by emitting water droplets or steam into the surrounding air, thereby raising the humidity.
The equilibrium moisture content (EMC) of a hygroscopic material surrounded at least partially by air is the moisture content at which the material is neither gaining nor losing moisture. The value of the EMC depends on the material and the relative humidity and temperature of the air with which it is in contact. The speed with which it is approached depends on the properties of the material, the surface-area-to-volume ratio of its shape, and the speed with which humidity is carried away or towards the material.
Water content or moisture content is the quantity of water contained in a material, such as soil, rock, ceramics, crops, or wood. Water content is used in a wide range of scientific and technical areas, and is expressed as a ratio, which can range from 0 to the value of the materials' porosity at saturation. It can be given on a volumetric or mass (gravimetric) basis.
Dry rot is wood decay caused by one of several species of fungi that digest parts of wood which give it strength and stiffness. It was previously used to describe any decay of cured wood in ships and buildings by a fungus which resulted in a darkly colored deteriorated and cracked condition.
Wood drying reduces the moisture content of wood before its use. When the drying is done in a kiln, the product is known as kiln-dried timber or lumber, whereas air drying is the more traditional method.
Tonewood refers to specific wood varieties used for woodwind or acoustic stringed instruments. The word implies that certain species exhibit qualities that enhance acoustic properties of the instruments, but other properties of the wood such as esthetics and availability have always been considered in the selection of wood for musical instruments. According to Mottola's Cyclopedic Dictionary of Lutherie Terms, tonewood is:
Wood that is used to make stringed musical instruments. The term is often used to indicate wood species that are suitable for stringed musical instruments and, by exclusion, those that are not. But the list of species generally considered to be tonewoods changes constantly and has changed constantly throughout history.
Moisture analysis covers a variety of methods for measuring the moisture content in solids, liquids, or gases. For example, moisture is a common specification in commercial food production. There are many applications where trace moisture measurements are necessary for manufacturing and process quality assurance. Trace moisture in solids must be known in processes involving plastics, pharmaceuticals and heat treatment. Fields that require moisture measurement in gasses or liquids include hydrocarbon processing, pure semiconductor gases, bulk pure or mixed gases, dielectric gases such as those in transformers and power plants, and natural gas pipeline transport. Moisture content measurements can be reported in multiple units, such as: parts per million, pounds of water per million standard cubic feet of gas, mass of water vapor per unit volume or mass of water vapor per unit mass of dry gas.
Fibre saturation point is a term used in wood mechanics and especially wood drying, to denote the point in the drying process at which only water bound in the cell walls remains - all other water, called free water, having been removed from the cell cavities. Further drying of the wood results in strengthening of the wood fibres, and is usually accompanied by shrinkage. Wood is normally dried to a point where it is in equilibrium with the atmospheric moisture content or relative humidity, and since this varies so does the equilibrium moisture content. Laboratory testing has found the average FSP in many types of wood to be approximately 26%. Individual species may differ from the average.
The conservation and restoration of parchment constitutes the care and treatment of parchment materials which have cultural and historical significance. Typically undertaken by professional book and document conservators, this process can include preventive measures which protect against future deterioration as well as specific treatments to alleviate changes already caused by agents of deterioration.
Mold or mould, also sometimes referred to as mildew, is a fungal growth that develops on wet materials. Mold is a natural part of the environment and plays an important part in nature by breaking down dead organic matter such as fallen leaves and dead trees; indoors, mold growth should be avoided. Mold reproduces by means of tiny spores. The spores are like seeds, but invisible to the naked eye, that float through the air and deposit on surfaces. When the temperature, moisture, and available nutrient conditions are correct, the spores can form into new mold colonies where they are deposited. There are many types of mold, but all require moisture and a food source for growth.
Green wood is wood that has been recently cut and therefore has not had an opportunity to season (dry) by evaporation of the internal moisture. Green wood contains more moisture than seasoned wood, which has been dried through passage of time or by forced drying in kilns. Green wood is considered to have 100% moisture content relative to air-dried or seasoned wood, which is considered to be 20%.
A concrete moisture meter is a type of moisture meter used by installers of flooring to measure the moisture levels of concrete. These meters have been used for decades to measure the moisture content in different materials and substances. Concrete meters have evolved from the successful wood moisture meter as flooring contractors tried to use their wood meters to measure the moisture in concrete.
Dynamic vapor sorption (DVS) is a gravimetric technique that measures how quickly and how much of a solvent is absorbed by a sample such as a dry powder absorbing water. It does this by varying the vapor concentration surrounding the sample and measuring the change in mass which this produces. The technique is mostly used for water vapor, but is suitable for a wide range of organic solvents. Daryl Williams, founder of Surface Measurement Systems Ltd, developed Dynamic Vapor Sorption in 1991; the first instrument was delivered to Pfizer UK in 1992. DVS was originally developed to replace the time and labor-intensive desiccators and saturated salt solutions used to measure water vapor sorption isotherms.
Rift sawing is a woodworking process that aims to produce lumber that is less vulnerable to distortion than flat-sawn lumber. Rift-sawing may be done strictly along a log's radials—perpendicular to the annular growth ring orientation or wood grain—or as part of the quarter sawing process.
Interstitial condensation is a type of condensation that may occur within an enclosed wall, roof or floor cavity structure, which can create dampening.