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61-517: 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

122-413: 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

183-406: 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

244-446: A brushable solution . The ingredients and processes of violin varnish are very diverse, with some highly regarded old examples showing defects (e.g. cracking, crazing) associated with incompatible varnish components. Some violin finishing systems use vernice bianca (egg white and gum arabic) as a sealer or ground. There is also evidence that finely powdered minerals, possibly volcanic ash, were used in some grounds. Some violins made in

305-409: 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

366-453: 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

427-453: A harder, decidedly tougher and more waterproof film. However, a thick film of ordinary polyurethane may de-laminate if subjected to heat or shock, fracturing the film and leaving white patches. This tendency increases with long exposure to sunlight or when it is applied over soft woods like pine . This is also in part due to polyurethane's lesser penetration into the wood. Various priming techniques are employed to overcome this problem, including

488-456: A multitude of lacquers . Synthetic resins such as phenolic resin may be employed as a secondary component in certain varnishes and paints. Over centuries, many recipes were developed which involved the combination of resins, oils, and other ingredients such as certain waxes . These were believed to impart special tonal qualities to musical instruments and thus were sometimes carefully guarded secrets. The interaction of different ingredients

549-586: 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

610-440: A straight oil finish, but because of the relatively slow curing time of oils, the emission of certain chemical byproducts, and the need for exposure to oxygen from the air, care must be taken that the oils are sufficiently cured to accept the polyurethane. One of the disadvantages of a polyurethane-based varnish is the tendency to yellow over time. This is because the hydroxyl groups of a regular alkyd are reacted with TDI to produce

671-460: A tendency to yellow over a fairly short period of time. Used when a fast-curing, tough, hard finish is desired, such as for kitchen cabinets and office furniture. Comes in two parts: a resin and an acid catalyst. The first is a blend of an amino resin and an alkyd. The acid catalyst is added right before application in a set ratio determined by the manufacturer. Most produce minimal yellowing. There are, however, two downsides to this finish. The first

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732-758: A true spar varnish maintained its elasticity above other virtues, even if this required a compromise in its UV-resistance. Spar varnishes are thus not necessarily the best choice for outdoor woodwork that does not need to bend in service. Despite this, the widespread perception of "marine products" as "tough" led to domestic outdoor varnishes being branded as "Spar varnish" and sold on the virtue of their weather- and UV-resistance. These claims may be more or less realistic, depending on individual products. Only relatively recently have spar varnishes been available that can offer both effective elasticity and UV-resistance. Drying oils, such as linseed and tung oil , are not true varnishes though often in modern terms they accomplish

793-399: A urethane-alkyd. This introduces a high degree of aromaticity and hence tendency to yellow. Unlike drying oils and alkyds which cure after evaporation of the solvent and upon reaction with oxygen from the air, true polyurethane coatings cure after evaporation of the solvent and then either by a variety of reactions of chemicals within the original mix, or by reaction with moisture from

854-425: A varnish effect by themselves. Originally, turpentine or alcohol was used to dissolve the resin and thin the drying oils. The invention of petroleum distillates has led to turpentine substitutes such as white spirit , paint thinner , and mineral spirit . Modern synthetic varnishes may be formulated with water instead of hydrocarbon solvents. Violin varnishing is a multi-step process involving some or all of

915-467: A wide range of conditions and can be engineered to speed up the cure rate and thus harden faster. Usually this is by the use of metal salt driers such as cobalt salts. Better (and more expensive) exterior varnishes employ alkyds made from high performance oils and contain UV -absorbers; this improves gloss-retention and extends the lifetime of the finish. Various resins may also be combined with alkyds as part of

976-464: 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

1037-414: 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

1098-402: 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

1159-474: Is a varnish. Thus, by far most pieces of wooden furniture are lacquered. Lacquer may be considered different from varnish because it can be re-dissolved later by a solvent (such as the one it was dissolved in when it was applied) and does not chemically change to a solid like other varnishes. Acrylic resin varnishes are typically water-borne varnishes with the lowest refractive index of all finishes and high transparency. They resist yellowing. Acrylics have

1220-687: Is also recorded in the history of East and South Asia; in India , China and Japan , where the practice of lacquer work, a species of varnish application, was known at a very early date. The Tang Chinese used medieval chemistry experiments to produce a varnish for clothes and weapons, employing complex chemical formulas applied to silk clothes of underwater divers , a cream designated for polishing bronze mirrors, and other formulas. Because of flammability concerns, many product containers list safety precautions for storage and disposal for varnishes and drying oils as they are flammable, and materials used to apply

1281-521: 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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1342-643: 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

1403-419: Is difficult to predict or reproduce, so expert finishers were often prized professionals. Shellac is a very widely used single-component resin varnish that is alcohol-soluble. It is not used for outdoor surfaces or where it will come into repeated contact with water, such as around a sink or bathtub. The source of shellac resin is a brittle or flaky secretion of the female lac insect, Kerria lacca , found in

1464-419: Is especially important with antiques. Varnish Varnish is a clear transparent hard protective coating or film. It is not to be confused with wood stain . It usually has a yellowish shade due to the manufacturing process and materials used, but it may also be pigmented as desired. It is sold commercially in various shades. Varnish is primarily used as a wood finish where, stained or not,

1525-498: 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

1586-497: 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

1647-426: Is not dissolved in alcohol. Lacquer is dissolved in lacquer thinner, which is a highly flammable solvent typically containing butyl acetate and xylene or toluene . Lacquer is typically sprayed on, within a spray booth that evacuates overspray and minimizes the risk of combustion. The rule of thumb is that a clear wood finish formulated to be sprayed is a lacquer, but if it is formulated to be brushed on then it

1708-401: Is typically available in "clear" and "amber" (or "orange") varieties, generally as "three-pound cut" or three pounds dry shellac to one US gallon of alcohol. Other natural color shades such as ruby and yellow are available from specialty pigment or woodworker's supply outlets. Dry shellac is available as refined flakes, "sticklac," "button lac," or "seedlac." "White pigmented" shellac primer paint

1769-424: 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

1830-491: Is widely available in retail outlets, billed as a fast-drying interior primer "problem solver", in that it adheres to a variety of surfaces and seals off odors and smoke stains. Shellac clean-up may be done either with pure alcohol or with ammonia cleansers. Modern commercially produced varnishes employ some form of alkyd for producing a protective film. Alkyds have good solvent, moisture and UV light resistance. Alkyds are chemically modified vegetable oils which operate well in

1891-564: The advantage of water clean-up and lack of solvent fumes, but typically do not penetrate into wood as well as oils. They sometimes lack the brushability and self-leveling qualities of solvent-based varnishes. Generally they have good UV-resistance. In the art world, varnishes offer dust-resistance and a harder surface than bare paint – they sometimes have the benefit of ultraviolet light resistors, which help protect artwork from fading in exposure to light. Acrylic varnish should be applied using an isolation coat (a permanent, protective barrier between

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1952-769: The air. Certain polyurethane products are "hybrids" and combine different aspects of their parent components. "Oil-modified" polyurethanes, whether water-borne or solvent-borne, are currently the most widely used wood floor finishes. Exterior use of polyurethane varnish may be problematic due to its heightened susceptibility to deterioration through ultra-violet light exposure. All clear or translucent varnishes, and indeed all film - polymer coatings (e.g. paint, stain , epoxy, synthetic plastic , etc.) are susceptible to this damage in varying degrees. Pigments in paints and stains protect against UV damage. UV-absorbers are added to polyurethane and other varnishes (e.g. spar varnish) to work against UV damage but are decreasingly effective over

2013-556: The ancient name of modern Benghazi in Libya, where the first varnishes in the Mediterranean area were supposedly used and where resins from the trees of now-vanished forests were sold. Early varnishes were developed by mixing resin —pine pitch , for example—with a solvent and applying them with a brush to get the golden and hardened effect one sees in today's varnishes. Varnishing was a technique well known in ancient Egypt . Varnishing

2074-407: 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

2135-411: The course of 2–4 years, depending on the quantity and quality of UV-absorbers added, as well as the severity and duration of sun exposure. Water exposure, humidity, temperature extremes, and other environmental factors affect all finishes. The word lacquer refers to quick-drying, solvent-based varnishes or paints. Although their names may be similarly derived, lacquer is not the same as shellac and

2196-461: The cure rate depends on the type of oil used and, to some extent, on the ratio of oil to resin. The drying and curing time of all varnishes may be sped up by exposure to an energy source such as sunlight , ultraviolet light, or heat. There are many different types of drying oils, including linseed oil , tung oil , and walnut oil . These contain high levels of polyunsaturated fatty acids . Drying oils cure through an exothermic reaction between

2257-663: The curing process are emitted from the oil film even after it is dry to the touch and over a considerable period of time. It has long been a tradition to combine drying oils with resins to obtain favourable features of both substances. Many different kinds of resins may be used to create a varnish. Natural resins used for varnish include amber , kauri gum , dammar , copal , rosin ( colophony or pine resin), sandarac , balsam , elemi , mastic , and shellac . Varnish may also be created from synthetic resins such as acrylic , alkyd , or polyurethane . A varnish formula might not contain any added resins at all since drying oils can produce

2318-468: The distinctive tones and grains in the wood are intended to be visible. Varnish finishes are naturally glossy , but satin/semi-gloss and flat sheens are available. The word "varnish" comes from Mediaeval Latin vernix , meaning odorous resin, perhaps derived from Middle Greek berōnikón or beroníkē , meaning amber or amber-colored glass. A false etymology traces the word to the Greek Berenice ,

2379-431: The finish, such as disposal in a water filled container. Varnish is traditionally a combination of a drying oil , a resin , and a thinner or solvent plus a metal drier to accelerate the drying. However, different types of varnish have different components. After being applied, the film-forming substances in varnishes either harden directly, as soon as the solvent has fully evaporated , or harden after evaporation of

2440-411: The following: primer, sealer, ground, color coats, and clear topcoat. Some systems use a drying oil varnish as described below, while others use spirit varnish made of resin(s) dissolved in alcohol. Touchup in repair or restoration is only done with solvent based varnish. Drying oil such as walnut oil or linseed oil may be used in combination with amber , copal , rosin or other resins . Traditionally

2501-497: The forests of Assam and Thailand and harvested from the bark of the trees where she deposits it to provide a sticky hold on the trunk. Shellac is the basis of French polish , which for centuries has been the preferred finish for fine furniture. Specified "dewaxed" shellac has been processed to remove the waxy substances from original shellac and can be used as a primer and sanding-sealer substrate for other finishes such as polyurethanes, alkyds, oils, and acrylics. Prepared shellac

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2562-401: The formula for typical "oil" varnishes that are commercially available. Spar varnish (also called marine varnish or yacht varnish ) was originally intended for use on ship or boat spars , to protect the timber from the effects of sea and weather. Spars bend under the load of their sails. The primary requirements were water resistance and also elasticity , so as to remain adhering as

2623-659: The late 18th century used ox blood to create a very deep-red coloration. Today this varnish would have faded and currently be a very warm, dark orange. Most resin or gum varnishes consist of a natural, plant- or insect-derived substance dissolved in a solvent, called spirit varnish or solvent varnish. The solvent may be alcohol , turpentine, or petroleum -based. Some resins are soluble in both alcohol and turpentine. Generally, petroleum solvents, i.e. mineral spirits or paint thinner , can substitute for turpentine. The resins include amber , dammar , copal , rosin , sandarac , elemi , benzoin , mastic , balsam , shellac , and

2684-435: The latex particles, and possibly chemical curing of the particles. Oil, polyurethane, and epoxy varnishes remain liquid even after evaporation of the solvent but quickly begin to cure, undergoing successive stages from liquid or syrupy, to tacky or sticky, to dry gummy, to dry to the touch, to hard. Environmental factors such as heat and humidity play a large role in the drying and curing times of varnishes. In classic varnish

2745-411: The oil is prepared by cooking or exposure to air and sunlight, but modern stand oil is prepared by heating oil at high temperature without oxygen. The refined resin is sometimes available as a translucent solid and is then "run" by cooking or melting it in a pot over heat without solvents. The thickened oil and prepared resin are then cooked together and thinned with turpentine (away from open flame) into

2806-422: The painting and the varnish, preferably a soft, glossy gel medium) to make varnish removal and overall conservation easier. Acrylic varnishes used for such a final removable art protection layer are typically mineral-spirit–based acrylic, rather than water-based. Various epoxy resin systems have been formulated as varnishes or floor finishes whereby two components are mixed directly before application. Sometimes,

2867-433: 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

2928-766: The polyunsaturated portion of the oil and oxygen from the air. Originally, the term "varnish" referred to finishes that were made entirely of resin dissolved in suitable solvents, either ethanol (alcohol) or turpentine . The advantage to finishes in previous centuries was that resin varnishes had a very rapid cure rate compared to oils; in most cases they are cured practically as soon as the solvent has fully evaporated. By contrast, untreated or "raw" oils may take weeks or months to cure, depending on ambient temperature and other environmental factors. In modern terms, boiled or partially polymerized drying oils with added siccatives or dryers (chemical catalysts ) have cure times of less than 24 hours. However, certain non-toxic by-products of

2989-399: 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

3050-647: 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

3111-431: The same thing. Polyurethane varnishes are typically hard, abrasion-resistant, and durable coatings. They are popular for hardwood floors but are considered by some wood finishers to be difficult or unsuitable for finishing furniture or other detailed pieces. Polyurethanes are comparable in hardness to certain alkyds but generally form a tougher film. Compared to simple oil or shellac varnishes, polyurethane varnish forms

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3172-422: The solvent through curing processes, primarily chemical reaction between oils and oxygen from the air ( autoxidation ) and chemical reactions between components of the varnish. Resin varnishes dry by evaporation of the solvent and harden quickly on drying. Acrylic and waterborne varnishes dry by evaporation of the water but will experience an extended curing period for evaporation of organic solvents absorbed on

3233-407: The spars flexed. Elasticity was a pre-condition for weatherproofing too, as a finish that cracked would then allow water through, even if the remaining film was impermeable. Appearance and gloss was of relatively low value. Modified tung oil and phenolic resins are often used. When first developed, no varnishes had good UV -resistance. Even after more modern synthetic resins did become resistant,

3294-400: 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

3355-474: 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

3416-482: The two parts are of equal volume and referred to as 1:1 but not always, as 2:1, 3:1, 4:1 and even 5:1 mixing ratios are commercially available. The individual components are usually referred to as Part A and Part B. All two-part epoxies have a pot-life or working time during which the mixed material can be used. Usually the pot-life is a matter of a few hours or less, but this is highly temperature dependent. Both water-borne and solvent-based epoxies are used. Epoxies do have

3477-742: 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

3538-446: The use of certain oil varnishes, specified "dewaxed" shellac, clear penetrating epoxy sealer, or "oil-modified" polyurethane designed for the purpose. Polyurethane varnish may also lack the "hand-rubbed" lustre of drying oils such as linseed or tung oil; in contrast, however, it is capable of a much faster and higher film build, accomplishing in two coats what may require multiple applications of oil. Polyurethane may also be applied over

3599-635: The varnishes may spontaneously combust. Many varnishes contain plant-derived oils (e.g. linseed oil ), synthetic oils (e.g. polyurethanes ) or resins as their binder in combination with organic solvents. These are flammable in their liquid state. All drying oils , certain alkyds (including paints ), and many polyurethanes produce heat (an exothermic reaction) during the curing process. Thus, oil-soaked rags and paper can smolder and ignite into flames, even several hours after use if proper precautions are not taken. Therefore, many manufacturers list proper disposal practices for rags and other items used to apply

3660-419: 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 "

3721-423: 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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