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71-517: There can be intentional stains (such as wood stains or paint ), indicative stains (such as food coloring dye, and staining , the use of one or more substances to enhance visibility of samples in a microscope or other imaging device. Numerous naturally-occurring stains exist, such as rust on iron and a patina on bronze , as do accidental stains such as from ketchup and oil on fabrics and other materials. Different types of material can be stained by different substances, and stain resistance

142-413: A chemical or molecular reaction between the material and the staining material. Many types of natural stains fall into this category. Finally, there can also be molecular attraction between the material and the staining material, involving being held in a covalent bond and showing the color of the bound substance. In many cases, stains are affected by heat and may become reactive enough to bond with

213-464: A chemical composition which includes what are referred to as absorption centers. Many substances are selective in their absorption of white light frequencies . They absorb certain portions of the visible spectrum while reflecting others. The frequencies of the spectrum which are not absorbed are either reflected or transmitted for our physical observation. This is what gives rise to color . The attenuation of light of all frequencies and wavelengths

284-406: A 'binder' which helps to adhere the pigments to the wood. A common binder would be a drying oil such as linseed oil. Most commercial stains contain both dyes and pigments, though often in varying colours and ratios (to each other) depending on the desired colouring effect. Additionally, to some extent, the degree to which a stain will colour a particular wood may be dependent on the length of time it

355-447: A boundary at a steep angle, the light will be completely reflected. This effect, called total internal reflection , is used in optical fibers to confine light in the core. Light travels along the fiber bouncing back and forth off of the boundary. Because the light must strike the boundary with an angle greater than the critical angle , only light that enters the fiber within a certain range of angles will be propagated. This range of angles

426-427: A fiber of silica glass that confines the incident light beam to the inside. In optical fibers, the main source of attenuation is scattering from molecular level irregularities, called Rayleigh scattering , due to structural disorder and compositional fluctuations of the glass structure . This same phenomenon is seen as one of the limiting factors in the transparency of infrared missile domes. Further attenuation

497-409: A finishing agent such as shellac , lacquer , varnish and polyurethane . Coloured or stained finishes do not typically deeply penetrate the pores of the wood and may largely disappear when the finish deteriorates or is removed. Stain is composed of the same three primary ingredients as paint (pigment, solvent (or vehicle), and binder) but is predominantly vehicle, then pigment and/or dye, and lastly

568-453: A greatly lengthened evaporation and curing period. New lumber , such as pine , can have waxlike sealants put on at the mill that will prevent proper staining; stripping or sanding the surface may be required. White stains composed of metal oxides, namely titanium dioxide and zinc oxide, do not penetrate well and remain on the surface. In such cases, wear easily reveals unstained wood. They are also fairly opaque. Thorough preparation of

639-400: A high transmission of ultraviolet light. Thus, when a material is illuminated, individual photons of light can make the valence electrons of an atom transition to a higher electronic energy level . The photon is destroyed in the process and the absorbed radiant energy is transformed to electric potential energy. Several things can happen, then, to the absorbed energy: It may be re-emitted by

710-403: A number of electrons (given by the atomic number Z in the periodic table ). Recall that all light waves are electromagnetic in origin. Thus they are affected strongly when coming into contact with negatively charged electrons in matter. When photons (individual packets of light energy) come in contact with the valence electrons of an atom, one of several things can and will occur: Most of

781-527: A portion of the incoming light. The remaining frequencies (or wavelengths) are free to be reflected or transmitted. This is how colored glass is produced. Most liquids and aqueous solutions are highly transparent. For example, water, cooking oil, rubbing alcohol, air, and natural gas are all clear. Absence of structural defects (voids, cracks, etc.) and molecular structure of most liquids are chiefly responsible for their excellent optical transmission. The ability of liquids to "heal" internal defects via viscous flow

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852-462: A range of wavelengths. Guided light wave transmission via frequency selective waveguides involves the emerging field of fiber optics and the ability of certain glassy compositions to act as a transmission medium for a range of frequencies simultaneously ( multi-mode optical fiber ) with little or no interference between competing wavelengths or frequencies. This resonant mode of energy and data transmission via electromagnetic (light) wave propagation

923-426: A regular lattice and a " sea of electrons " moving randomly between the atoms. In metals, most of these are non-bonding electrons (or free electrons) as opposed to the bonding electrons typically found in covalently bonded or ionically bonded non-metallic (insulating) solids. In a metallic bond, any potential bonding electrons can easily be lost by the atoms in a crystalline structure. The effect of this delocalization

994-491: A relatively low cost. These components are free of internal stress or intrinsic birefringence , and allow relatively large doping levels or optimized custom-designed doping profiles. This makes ceramic laser elements particularly important for high-energy lasers. The development of transparent panel products will have other potential advanced applications including high strength, impact-resistant materials that can be used for domestic windows and skylights. Perhaps more important

1065-586: A small amount of binder. Much like the dyeing or staining of fabric, wood stain is designed to add colour to the substrate (wood and other materials) while leaving some of the substrate still visible. Transparent varnishes or surface films are applied afterwards. In principle, stains do not provide a durable surface coating or film. However, because the binders are from the same class of film-forming binders that are used in paints and varnishes, some build-up of film occurs. Pigments and/or dyes are largely used as colourants in most stains. The difference between

1136-433: A trade-off between optical performance, mechanical strength and price. For example, sapphire (crystalline alumina ) is very strong, but it is expensive and lacks full transparency throughout the 3–5 μm mid-infrared range. Yttria is fully transparent from 3–5 μm, but lacks sufficient strength, hardness, and thermal shock resistance for high-performance aerospace applications. A combination of these two materials in

1207-419: A typical metal or ceramic object are in the form of grain boundaries , which separate tiny regions of crystalline order. When the size of the scattering center (or grain boundary) is reduced below the size of the wavelength of the light being scattered, the scattering no longer occurs to any significant extent. In the formation of polycrystalline materials (metals and ceramics) the size of the crystalline grains

1278-464: Is a natural alternative to synthetic wood stain. The initial application of any paint or varnish is similarly absorbed into the substrate, but because stains contain lower amounts of binder, the binder from a stain resides mainly below the surface while the pigment remains near the top or at the surface. Stains that employ metallic pigments such as iron oxides usually are more opaque; first because metallic pigments are opaque by nature, but also because

1349-414: Is a result of a combination of the stain and properties of the wood. For example, although medium-to-dark stains tend to look blotchy on maple, they get deeper and more glowing on cherry, with a more consistent colouration. Stains that are fast drying will be difficult to apply in hot weather or in direct sunlight. Stains that are slow-drying will be difficult to work with in damp and cold conditions due to

1420-402: Is a type of paint used to colour wood comprising colourants dissolved and/or suspended in a vehicle or solvent . Pigments and/or dyes are largely used as colourants in most stains. The initial application of any paint or varnish is absorbed into the substrate similarly to stains, but the binder from a stain resides mainly below the surface while the pigment remains near the top or at

1491-521: Is an important characteristic in modern textile engineering . The primary method of stain formation is surface stains, where the staining substance is spilled out onto the surface or material and is trapped in the fibers, pores, indentations, or other capillary structures on the surface. The material that is trapped coats the underlying material, and the stain reflects backlight according to its own color. Applied paint, spilled food, and wood stains are of this nature. A secondary method of stain involves

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1562-462: Is called the acceptance cone of the fiber. The size of this acceptance cone is a function of the refractive index difference between the fiber's core and cladding. Optical waveguides are used as components in integrated optical circuits (e.g., combined with lasers or light-emitting diodes , LEDs) or as the transmission medium in local and long-haul optical communication systems. Attenuation in fiber optics , also known as transmission loss ,

1633-481: Is caused by light absorbed by residual materials, such as metals or water ions, within the fiber core and inner cladding. Light leakage due to bending, splices, connectors, or other outside forces are other factors resulting in attenuation. At high optical powers, scattering can also be caused by nonlinear optical processes in the fiber. Many marine animals that float near the surface are highly transparent, giving them almost perfect camouflage . However, transparency

1704-508: Is dependent upon the frequency of the light, the nature of the atoms in the object, and often, the nature of the electrons in the atoms of the object. Some materials allow much of the light that falls on them to be transmitted through the material without being reflected. Materials that allow the transmission of light waves through them are called optically transparent. Chemically pure (undoped) window glass and clean river or spring water are prime examples of this. Materials that do not allow

1775-643: Is designed primarily to form a protective surface film. Some products are marketed as a combination of stain and varnish. Siding stain is one variety of wood stain with very high viscosity (others can be quite thin). Effectively, siding stains are paints that do not cover as well and do not form a hard film. They are designed to penetrate better and contain binders that are softer and more flexible, allowing them to last longer than harder, more brittle paints. Siding stain protects against solar radiation especially UV radiation , water , fungus including mildew , and insects . Different siding stains are distinguished by

1846-416: Is determined largely by the size of the crystalline particles present in the raw material during formation (or pressing) of the object. Moreover, the size of the grain boundaries scales directly with particle size. Thus, a reduction of the original particle size well below the wavelength of visible light (about 1/15 of the light wavelength, or roughly 600 nm / 15 = 40  nm ) eliminates much of

1917-536: Is difficult for bodies made of materials that have different refractive indices from seawater. Some marine animals such as jellyfish have gelatinous bodies, composed mainly of water; their thick mesogloea is acellular and highly transparent. This conveniently makes them buoyant , but it also makes them large for their muscle mass, so they cannot swim fast, making this form of camouflage a costly trade-off with mobility. Gelatinous planktonic animals are between 50 and 90 percent transparent. A transparency of 50 percent

1988-423: Is due to the combined mechanisms of absorption and scattering . Transparency can provide almost perfect camouflage for animals able to achieve it. This is easier in dimly-lit or turbid seawater than in good illumination. Many marine animals such as jellyfish are highly transparent. With regard to the absorption of light, primary material considerations include: With regard to the scattering of light ,

2059-435: Is enough to make an animal invisible to a predator such as cod at a depth of 650 metres (2,130 ft); better transparency is required for invisibility in shallower water, where the light is brighter and predators can see better. For example, a cod can see prey that are 98 percent transparent in optimal lighting in shallow water. Therefore, sufficient transparency for camouflage is more easily achieved in deeper waters. For

2130-410: Is especially important with antiques. Transparency and translucency In the field of optics , transparency (also called pellucidity or diaphaneity ) is the physical property of allowing light to pass through the material without appreciable scattering of light . On a macroscopic scale (one in which the dimensions are much larger than the wavelengths of the photons in question),

2201-498: Is in a vertical position, which can often cause traditional liquid stains to run, drip, or pool. Gel stains often have limited penetrating ability, as they are thixotropic (a liquid that nevertheless does not flow ). Applying stains can be very easy or very difficult depending on the type of substrate, type of stain, and the ambient conditions. Fresh, "green" lumber accepts stain poorly, while aged wood absorbs stains relatively well. Porosity of wood can vary greatly, even within

Stain - Misplaced Pages Continue

2272-497: Is left on the wood, with longer exposure times accomplishing deeper colouration. Typically a 'transparent' stain will accentuate the wood grain (as it is transparent), while a more 'solid' stain will tend to obscure the wood grain (as it is more opaque, akin to what we would usually call 'paint'). Pigments, regardless of the suspension agent, will not give much colour to very dense woods but will deeply colour woods with large pores (e.g. pine). A combination of coffee and vinegar or water

2343-414: Is made up of components with a uniform index of refraction. Transparent materials appear clear, with the overall appearance of one color, or any combination leading up to a brilliant spectrum of every color. The opposite property of translucency is opacity . Other categories of visual appearance, related to the perception of regular or diffuse reflection and transmission of light, have been organized under

2414-494: Is motion at the atomic and molecular levels. The primary mode of motion in crystalline substances is vibration . Any given atom will vibrate around some mean or average position within a crystalline structure, surrounded by its nearest neighbors. This vibration in two dimensions is equivalent to the oscillation of a clock's pendulum. It swings back and forth symmetrically about some mean or average (vertical) position. Atomic and molecular vibrational frequencies may average on

2485-405: Is one of the reasons why some fibrous materials (e.g., paper or fabric) increase their apparent transparency when wetted. The liquid fills up numerous voids making the material more structurally homogeneous. Light scattering in an ideal defect-free crystalline (non-metallic) solid that provides no scattering centers for incoming light will be due primarily to any effects of anharmonicity within

2556-401: Is relatively lossless. An optical fiber is a cylindrical dielectric waveguide that transmits light along its axis by the process of total internal reflection . The fiber consists of a core surrounded by a cladding layer. To confine the optical signal in the core, the refractive index of the core must be greater than that of the cladding. The refractive index is the parameter reflecting

2627-400: Is simply to exaggerate the effect of the "sea of electrons". As a result of these electrons, most of the incoming light in metals is reflected back, which is why we see a shiny metal surface. Most insulators (or dielectric materials) are held together by ionic bonds . Thus, these materials do not have free conduction electrons , and the bonding electrons reflect only a small fraction of

2698-465: Is that walls and other applications will have improved overall strength, especially for high-shear conditions found in high seismic and wind exposures. If the expected improvements in mechanical properties bear out, the traditional limits seen on glazing areas in today's building codes could quickly become outdated if the window area actually contributes to the shear resistance of the wall. Currently available infrared transparent materials typically exhibit

2769-406: Is the reduction in intensity of the light beam (or signal) with respect to distance traveled through a transmission medium. It is an important factor limiting the transmission of a signal across large distances. Attenuation coefficients in fiber optics usually use units of dB/km through the medium due to the very high quality of transparency of modern optical transmission media. The medium is usually

2840-424: Is usually the preferred sandpaper for hand-sanding bare wood; this is due to a sharper and faster cutting grit, and because it does not impart colour from the grit, as aluminium oxide or silicon carbide can do. Other methods include "rubbing" with rottenstone etc. In certain cases it is necessary to clean the wood or remove existing stains prior to staining the wood with a commercial stain in order to avoid damaging

2911-403: The speed of light in a material. (Refractive index is the ratio of the speed of light in vacuum to the speed of light in a given medium. The refractive index of vacuum is therefore 1.) The larger the refractive index, the more slowly light travels in that medium. Typical values for core and cladding of an optical fiber are 1.48 and 1.46, respectively. When light traveling in a dense medium hits

Stain - Misplaced Pages Continue

2982-407: The appearance they impart to wood. Certain solvent-based or oil-based siding stains contain small amounts of paraffin wax , which cannot be painted over, although re-staining is still possible. Gel stains are a late 20th century innovation in stain manufacturing, in that they are high-viscosity liquids and do not 'flow'. This property allows more control during application, particularly when the wood

3053-488: The concept of cesia in an order system with three variables, including transparency, translucency and opacity among the involved aspects. When light encounters a material, it can interact with it in several different ways. These interactions depend on the wavelength of the light and the nature of the material. Photons interact with an object by some combination of reflection, absorption and transmission. Some materials, such as plate glass and clean water , transmit much of

3124-472: The electron as radiant energy (in this case, the overall effect is in fact a scattering of light), dissipated to the rest of the material (i.e., transformed into heat ), or the electron can be freed from the atom (as in the photoelectric effects and Compton effects ). The primary physical mechanism for storing mechanical energy of motion in condensed matter is through heat , or thermal energy . Thermal energy manifests itself as energy of motion. Thus, heat

3195-476: The emerging chemical processing methods encompassed by the methods of sol-gel chemistry and nanotechnology . Transparent ceramics have created interest in their applications for high energy lasers, transparent armor windows, nose cones for heat seeking missiles, radiation detectors for non-destructive testing, high energy physics, space exploration, security and medical imaging applications. Large laser elements made from transparent ceramics can be produced at

3266-561: The form of the yttrium aluminium garnet (YAG) is one of the top performers in the field. When light strikes an object, it usually has not just a single frequency (or wavelength) but many. Objects have a tendency to selectively absorb, reflect, or transmit light of certain frequencies. That is, one object might reflect green light while absorbing all other frequencies of visible light. Another object might selectively transmit blue light while absorbing all other frequencies of visible light. The manner in which visible light interacts with an object

3337-411: The frequency of the incoming light wave is at or near the energy levels of the electrons within the atoms that compose the substance. In this case, the electrons will absorb the energy of the light wave and increase their energy state, often moving outward from the nucleus of the atom into an outer shell or orbital . The atoms that bind together to make the molecules of any particular substance contain

3408-410: The frequency of the light wave and the physical dimension of the scattering center. For example, since visible light has a wavelength scale on the order of a micrometre, scattering centers will have dimensions on a similar spatial scale. Primary scattering centers in polycrystalline materials include microstructural defects such as pores and grain boundaries. In addition to pores, most of the interfaces in

3479-407: The incident wave. The remaining frequencies (or wavelengths) are free to propagate (or be transmitted). This class of materials includes all ceramics and glasses . If a dielectric material does not include light-absorbent additive molecules (pigments, dyes, colorants), it is usually transparent to the spectrum of visible light. Color centers (or dye molecules, or " dopants ") in a dielectric absorb

3550-510: The light scattering, resulting in a translucent or even transparent material. Computer modeling of light transmission through translucent ceramic alumina has shown that microscopic pores trapped near grain boundaries act as primary scattering centers. The volume fraction of porosity had to be reduced below 1% for high-quality optical transmission (99.99 percent of theoretical density). This goal has been readily accomplished and amply demonstrated in laboratories and research facilities worldwide using

3621-401: The light that falls on them and reflect little of it; such materials are called optically transparent. Many liquids and aqueous solutions are highly transparent. Absence of structural defects (voids, cracks, etc.) and molecular structure of most liquids are mostly responsible for excellent optical transmission. Materials that do not transmit light are called opaque . Many such substances have

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3692-440: The material (e.g., the grain boundaries of a polycrystalline material or the cell or fiber boundaries of an organic material), and by its surface, if it is rough. Diffuse reflection is typically characterized by omni-directional reflection angles. Most of the objects visible to the naked eye are identified via diffuse reflection. Another term commonly used for this type of reflection is "light scattering". Light scattering from

3763-413: The material and re-emitted on the opposite side of the object. Such frequencies of light waves are said to be transmitted. An object may be not transparent either because it reflects the incoming light or because it absorbs the incoming light. Almost all solids reflect a part and absorb a part of the incoming light. When light falls onto a block of metal , it encounters atoms that are tightly packed in

3834-406: The most critical factor is the length scale of any or all of these structural features relative to the wavelength of the light being scattered. Primary material considerations include: Diffuse reflection - Generally, when light strikes the surface of a (non-metallic and non-glassy) solid material, it bounces off in all directions due to multiple reflections by the microscopic irregularities inside

3905-443: The order of 0.5  μm . Scattering centers (or particles) as small as 1 μm have been observed directly in the light microscope (e.g., Brownian motion ). Optical transparency in polycrystalline materials is limited by the amount of light scattered by their microstructural features. Light scattering depends on the wavelength of the light. Limits to spatial scales of visibility (using white light) therefore arise, depending on

3976-460: The order of 10 cycles per second ( Terahertz radiation ). When a light wave of a given frequency strikes a material with particles having the same or (resonant) vibrational frequencies, those particles will absorb the energy of the light wave and transform it into thermal energy of vibrational motion. Since different atoms and molecules have different natural frequencies of vibration, they will selectively absorb different frequencies (or portions of

4047-430: The ordered lattice. Light transmission will be highly directional due to the typical anisotropy of crystalline substances, which includes their symmetry group and Bravais lattice . For example, the seven different crystalline forms of quartz silica ( silicon dioxide , SiO 2 ) are all clear, transparent materials . Optically transparent materials focus on the response of a material to incoming light waves of

4118-433: The particles of which they consist are much larger than organic pigments and therefore do not penetrate as well. Most wood stains for interior uses (e.g. floors and furniture) require a secondary application of varnish or finish for longer-term protection of the wood, and also to adjust for matte or gloss effects. Stains are differentiated from varnishes in that the latter usually has no significant added colour or pigment and

4189-475: The photons can be said to follow Snell's law . Translucency (also called translucence or translucidity ) allows light to pass through but does not necessarily (again, on the macroscopic scale) follow Snell's law; the photons can be scattered at either of the two interfaces, or internally, where there is a change in the index of refraction . In other words, a translucent material is made up of components with different indices of refraction. A transparent material

4260-399: The relative transparency or opaqueness may fall somewhere between the two extremes. Typically, dyes will colour very fine-grained woods (such as cherry or maple) while pigments will not colour woods such as these as well. Fine-grained woods generally have pores that are too small for the pigments to settle into. As a result, usually pigment-containing stains will also include a small amount of

4331-647: The same piece of wood. End grain and bias-cut grain are far more absorbent, thus will accept more pigment and will darken considerably in those areas. The hard ring may absorb differently from the soft ring. The characteristic medullary rays in oak will absorb much less and remain mostly blonde . Woods that have been heavily subjected to paint strippers or washed down with detergents or solvents will have an increased open grain and accept substantially more stain than normal. Woods from different species of trees can have huge variations in how well they take stain. Different wood species stain differently—the overall colour and shade

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4402-407: The spectrum) of infrared light. Reflection and transmission of light waves occur because the frequencies of the light waves do not match the natural resonant frequencies of vibration of the objects. When infrared light of these frequencies strikes an object, the energy is reflected or transmitted. If the object is transparent, then the light waves are passed on to neighboring atoms through the bulk of

4473-400: The surface. Wood stain is a type of paint used to colour wood . It consists of colourants dissolved and/or suspended in a vehicle or solvent . Vehicle is the preferred term, as the contents of a stain may not be truly dissolved in the vehicle, but rather suspended , and thus the vehicle may not be a true solvent. The vehicle often may be water, alcohol , a petroleum distillate , or

4544-407: The surfaces of objects is our primary mechanism of physical observation. Light scattering in liquids and solids depends on the wavelength of the light being scattered. Limits to spatial scales of visibility (using white light) therefore arise, depending on the frequency of the light wave and the physical dimension (or spatial scale) of the scattering center. Visible light has a wavelength scale on

4615-586: The time, it is a combination of the above that happens to the light that hits an object. The states in different materials vary in the range of energy that they can absorb. Most glasses, for example, block ultraviolet (UV) light. What happens is the electrons in the glass absorb the energy of the photons in the UV range while ignoring the weaker energy of photons in the visible light spectrum. But there are also existing special glass types, like special types of borosilicate glass or quartz that are UV-permeable and thus allow

4686-469: The transmission of any light wave frequencies are called opaque . Such substances may have a chemical composition which includes what are referred to as absorption centers. Most materials are composed of materials that are selective in their absorption of light frequencies. Thus they absorb only certain portions of the visible spectrum. The frequencies of the spectrum which are not absorbed are either reflected back or transmitted for our physical observation. In

4757-474: The two is in the solubility and in the size of the particles. While dyes are molecules that dissolve into the vehicle, pigments are larger than molecules and are temporarily suspended in the vehicle, usually settling out over time. Stains with primarily dye content are said to be 'transparent', while stains with more pigment in them are said to be 'solid' (opaque); some stains may be called 'semi-solid' or 'semi-transparent', and these may be interchangeable terms, and

4828-746: The underlying material. Applied heat, such as from ironing , dry cleaning or sunlight , can cause a chemical reaction on an otherwise removable stain, turning it into a chemical. Various laundry techniques exist to attempt to remove or reduce existing stains. Stain removal is frequently a highly desired characteristic in laundry detergents and other types of cleaning agent. Some agents are designed to be applied directly onto stains. The removal of some types of stains requires other chemicals or special techniques. Use of an inappropriate technique could make permanent an otherwise removable stain or cause unwanted discoloration of clothing. Wood stain Wood stain

4899-535: The visible portion of the spectrum, this is what gives rise to color. Absorption centers are largely responsible for the appearance of specific wavelengths of visible light all around us. Moving from longer (0.7 μm) to shorter (0.4 μm) wavelengths: Red, orange, yellow, green, and blue (ROYGB) can all be identified by our senses in the appearance of color by the selective absorption of specific light wave frequencies (or wavelengths). Mechanisms of selective light wave absorption include: In electronic absorption,

4970-419: The wood (usually by sanding) is necessary to obtain equal absorption of the stain and thus an even finish. White stain on a bare softwood or oak floor might require a final 'prep' sanding by hand with an orbital/vibrating sander with 80 or 100 grit, whereas certain hardwoods might be orbitally or hand sanded with 220 grit and higher for a darkish organic stain on furniture. Though it is not as durable, " garnet "

5041-423: The wood. This can be the case for both unfinished and finished wood. There are special considerations when cleaning stained wood. One of the most common stains is water stains on stained wood. Techniques to remove water stains have been documented which use a hot iron to remove the water stain. Special caution should be used when trying to remove stains from a stained wood to avoid damaging the original stain. This

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