Varnish is a transparent, hard, protective finish or film primarily used in wood finishing but also for other materials. In Optics, transparency (also called pellucidity) is the Material property of allowing Wood finishing refers to the process of embellishing and/or protecting the surface Varnish is traditionally a combination of a drying oil, a resin, and a thinner or solvent. A drying oil is an Oil which hardens to a tough solid film after a period of exposure to air Resin, not to be confused with Rosin, is a Hydrocarbon Secretion of many Plants particularly coniferous trees. Mineral turpentine, also known as turpentine substitute, turps substitute, or just Turps is an inexpensive Petroleum -based A solvent is a liquid or gas that dissolves a solid liquid or gaseous Solute, resulting in a Solution. Varnish finishes are usually glossy but may be designed to produce satin or semi-gloss sheens by the addition of "flatting" agents. This article is about the literary term For other uses see Gloss (disambiguation. Satin is a Cloth that typically has a glossy surface and a dull back Varnish has little or no color, is transparent, and has no added pigment, as opposed to paints or wood stains, which contain pigment and generally range from opaque to translucent. For the drug referred to as "pigment" see Black tar heroin. Paint is any Liquid, liquifiable or mastic composition which after application to a substrate in a thin layer is converted to an opaque Solid A Wood stain, is a sub-category of Paint, consists of a Pigment suspended in a "vehicle" of Solvent and binding agent ( Alkyd, Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation especially visible Light. Opacity is the measure of impenetrability to electromagnetic or other kinds of radiation especially visible Light. Varnishes are also applied over wood stains as a final step to achieve a film for gloss and protection. Some products are marketed as a combined stain and varnish.
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 the solvent through certain curing processes, primarily chemical reaction between oils and oxygen from the air (autoxidation) and chemical reactions between components of the varnish. Evaporation is the process by which Molecules in a Liquid state (e Autoxidation is any Oxidation that occurs in open air or in presence of Oxygen and/or UV radiation and forms Peroxides and Hydroperoxides Resin varnishes "dry" by evaporation of the solvent and harden almost immediately upon drying. Acrylic and waterborne varnishes "dry" upon evaporation of the water but experience an extended curing period. 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. A cure is a substance or procedure that makes a sick or diseased person well Environmental factors such as heat and humidity play a very large role in the drying and curing times of varnishes. In classic varnish 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 speeded up by exposure to an energy source such as sunlight or heat. Sunlight, in the broad sense is the total spectrum of the Electromagnetic radiation given off by the Sun. Other than acrylic and waterborne types, all varnishes are highly flammable in their liquid state due to the presence of flammable solvents and oils. All drying oils, certain alkyds, and many single-component polyurethanes produce heat during the curing process. Therefore, oil-soaked rags and paper can literally burst into flame hours after application if they are bunched or piled together, or, for example, placed in a container where the heat cannot dissipate. Spread rags and paper out to dry. As an added safety measure, douse the waste materials with water prior to drying. Alternatively they can be submersed in water in an airtight metal container and kept for later use or disposal. Check with manufacturer for details.
The word "varnish" comes from Latin vernix meaning odorous resin, which etymology comes from Greek Berenice, ancient name of modern Bengasi in Libya, credited with the first use of varnishes. Berenice comes from the Greek words phero (to bring) + nike (victory).
Contents |
Components of Classic Varnish
Drying oil
There are many different types of drying oils, including linseed oil, tung oil, and walnut oil. Linseed oil, also known as flax seed oil or simply flax oil, is a clear to yellowish Drying oil derived from the dried ripe seeds of the Flax Tung oil is used as a Wood finishing product It has two distinct meanings pure tung oil and tung oil finishes, which are often confused Walnut oil is oil extracted from Walnuts Culinary use Walnut oil is not used as extensively as other oils in Food preparation due to cost These contain high levels of polyunsaturated fatty acids. In nutrition polyunsaturated fat is an abbreviation of polyunsaturated Fatty acid. In Chemistry, especially Biochemistry, a fatty acid is a Carboxylic acid often with a long unbranched Aliphatic tail ( chain) which
Resin
Resins that are used in varnishes include amber, kauri gum, dammar, copal, rosin (pine resin), sandarac, balsam, and others. Amber is Fossil tree Resin, which is appreciated for its color and beauty Gum-diggers were men and women who dug for kauri gum a fossilised Resin, in the old kauri fields of New Zealand at the end of the nineteenth Dammar gum is obtained from the Dipterocarpaceae family of trees in India and East Asia, principally those of the genera Copal is a type of Resin produced from plant or tree secretions, often taken from members of the genus Copaifera. Rosin, formerly called colophony or Greek pitch ( Pix græca) is a solid form of Resin obtained from Pines and some other Plants In Mineralogy, sandarac, or sandarach, may refer to Realgar or native arsenic disulfide but is generally (a use found in Dioscorides) a Balsam of Mecca (or balsam of Gilead or balm of Gilead) is a Resinous gum of the tree Commiphora gileadensis (syn The word varnish probably derives ultimately via ancient Greek from a placename of a city in ancient Libya where resins from the trees of once existing forests were sold. Toponymy refers to the scientific study of place-names ( toponyms) their origins meanings use and Typology. Libya ( ليبيا ar-Latn Lībiyā; Libyan vernacular: Lībya; Amazigh:) officially the Great Socialist People's Libyan Arab In modern English the ancient city is referred to as Berenice; otherwise the existing city in modern Libya is called Benghazi. Berenice or Berenike ( Greek:, Berenikē) is the Ancient Macedonian form for Attic Greek Φερενίκη ( Pherenikē Benghazi or Bengasi ( Arabic بنغازي, transliterated Banġāzī,) is the second largest city in Libya and the
Turpentine or solvent
Traditionally, natural (organic) turpentine was used as the thinner or solvent, but has been replaced by several mineral based turpentine substitutes such as white spirit or "paint thinner". Turpentine (also called spirit of turpentine oil of turpentine wood turpentine gum turpentine is a fluid obtained by the Distillation of Resin obtained from trees Mineral turpentine, also known as turpentine substitute, turps substitute, or just Turps is an inexpensive Petroleum -based White spirit, also known as Stoddard solvent, is a Paraffin -derived clear transparent liquid which is a common organic Solvent used in painting and
Types
Violin
For violin varnish, walnut oil and linseed oil are most often used in combination with amber, copal, rosin or other resins. The oil is prepared by cooking or exposing to air and sunlight. The refined resin is typically available as a translucent solid and is then "run" by cooking or literally 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 a brushable solution.
Resin
Most resin or "gum" varnishes consist of a natural, plant- or insect-derived substance dissolved in a solvent. The two main types of natural varnishes are spirit varnish (which uses alcohol as a solvent) and turpentine or petroleum-based varnish. In Chemistry, an alcohol is any Organic compound in which a Hydroxyl group ( - O[[hydrogen H]]) is bound to a Carbon Petroleum ( L petroleum, from Greek πετρέλαιον, lit Some resins are soluble in both alcohol and turpentine. Generally, petroleum solvents, i. e. mineral spirits or paint thinner, can substitute for turpentine. Mineral Spirits, also called Stoddard solvent 8052-41-3 is a petroleum distilate commonly used as a paint thinner and mild Solvent. A paint thinner is a Solvent used to thin oil-based paints or as a cleaning agent The resins include amber, dammar, copal, rosin {pine resin}, sandarac, balsam, shellac, and a multitude of lacquers. Shellac is the commercial resin marketed in the form of amber flakes made from Lac, the secretion of the family of lac-producing insects though most commonly from the In a general sense lacquer is a clear or coloured Varnish, that dries by solvent evaporation and often a curing process as well that produces a hard durable finish in any Synthetic resins such as phenolic resin are typically employed as a secondary component in certain varnishes and paints. In Chemistry, chemical synthesis is purposeful execution of Chemical reactions in order to get a product, or several products Over centuries, many recipes were developed which involved the combination of resins, oils, and other ingredients such as certain waxes. Wax has traditionally referred to a substance that is secreted by Bees ( Beeswax) and used by them in constructing their These were believed to impart special tonal qualities to musical instruments and thus were sometimes carefully guarded secrets. The interaction of different ingredients is difficult to predict or reproduce, so expert finishers were often prized professionals.
Shellac
Shellac is a very widely used single component resin varnish that is alcohol soluble. Shellac is the commercial resin marketed in the form of amber flakes made from Lac, the secretion of the family of lac-producing insects though most commonly from the Shellac is the commercial resin marketed in the form of amber flakes made from Lac, the secretion of the family of lac-producing insects though most commonly from the 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 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. Lac is the scarlet resinous secretion of a number of species of Lac-producing insects the most commonly cultivated of which is Kerria lacca. Lac is the scarlet resinous secretion of a number of species of Lac-producing insects the most commonly cultivated of which is Kerria lacca. Assam) ( Assamese: অসম Ôxôm) is a northeastern state of India with its capital at Dispur, a suburb of the city The Kingdom of Thailand (ˈtaɪlænd ราชอาณาจักรไทย, râːtɕʰa-ʔaːnaːtɕɑ̀k-tʰɑj Shellac is the basis of French polish, a difficult technique that produces an inimitable sheen, and which for centuries has been the preferred finish for fine furniture. French polishing is a Wood finishing technique that results in a very high gloss deep colour and tough surface 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.
Shellac varnish is typically available in "clear" and "amber" (or "orange") varieties. Other natural color shades such as ruby and yellow are available from specialty pigment or woodworker's supply outlets. "White pigmented" shellac primer paint 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. Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor
Alkyd
Typically, modern commercially produced varnishes employ some form of alkyd for producing a protective film. Alkyd coatings are a class of Polyester coatings derived from the reaction of an Alcohol (alkohol and an acid or acid Anhydride hence the term alk-yd from Alkyds are chemically modified vegetable oils which operate well in a wide range of conditions and can be engineered to speed up the cure rate and thus harden faster. Alkyd coatings are a class of Polyester coatings derived from the reaction of an Alcohol (alkohol and an acid or acid Anhydride hence the term alk-yd from 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. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Various resins may also be combined with alkyds as part of the formula for typical "oil" varnishes that are commercially available.
Spar Varnish
Spar varnish (also called marine varnish) is high quality, waterproof, and sunlight-resistant varnish named for its use on ship or boat spars and other woodwork where a glossy finish is desired. Marine is an Umbrella term. As an adjective it is usually applicable to things relating to the Sea or Ocean, such as Marine biology, Marine A ship /ʃɪp/ is a large vessel that floats on water Ships are generally distinguished from Boats based on size A boat is a Watercraft of modest size designed to float or plane on water and provide transport over it In Sailing, a spar is also know as a round pole of wood or Metal used on a Sailing ship. Modified tung oil and phenolic resins are often used. Tung oil is used as a Wood finishing product It has two distinct meanings pure tung oil and tung oil finishes, which are often confused Better grades of spar varnish have substantially higher amounts of uv-absorbers added. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays
Drying Oils
By definition, drying oils, such as linseed and tung oil, are not true varnishes though often in modern terms they accomplish the same thing. Flax (also known as common flax or linseed) (binomial name Linum usitatissimum) is a member of the genus Linum Drying oils cure through an exothermic reaction between the polyunsaturated portion of the oil and oxygen from the air. In Thermodynamics, the word exothermic "outside heating" describes a process or reaction that releases Energy usually in the form of Heat, but Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the 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 finishers 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. A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst However, certain non-toxic byproducts of 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 favorable features of both substances .
Polyurethane
Polyurethane varnishes are typically hard, abrasion-resistant, and durable coatings. A polyurethane, commonly abbreviated PU, is any Polymer consisting of a chain of organic units joined by urethane links They are popular for hardwood floors but are considered by some to be difficult or unsuitable for finishing furniture or other detailed pieces. The term hardwood is used to describe Wood from broad-leaved angiosperm Trees mostly Deciduous, but not necessarily in the case of tropical Polyurethanes are comparable in hardness to certain alkyds but generally form a tougher film. Compared to simple oil or shellac varnishes, polyurethane varnish forms 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 article is about the tree For other uses of the term "pine" see Pine (disambiguation. This is also in part due to polyurethane's lesser penetration into the wood. Various priming techniques are employed to overcome this problem, including the use of certain oil varnishes, specified "dewaxed" shellac, clear penetrating epoxy sealer, or "oil-modified" polyurethane designed for the purpose. In Chemistry, epoxy or polyepoxide is a Thermosetting Epoxide Polymer that cures (polymerizes and crosslinks when mixed with a 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 "build" of film, accomplishing in two coats what may require multiple applications of oil. Polyurethane may also be applied over 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.
Unlike drying oils and alkyds which cure, after evaporation of the solvent, upon reaction with oxygen from the air, true polyurethane coatings cure after evaporation of the solvent by a variety of reactions of chemicals within the original mix, or by reaction with moisture from the air. Evaporation is the process by which Molecules in a Liquid state (e A chemical substance is a Material with a definite chemical composition. 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. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays It must be noted, however, that all clear or transluscent varnishes, and indeed all film-polymer coatings (e. A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds g. paint, stain, epoxy, synthetic plastic, etc. A stain is a discoloration that can be clearly distinguished from the sufrace Plastic is the general common term for a wide range of synthetic or semisynthetic organic solid materials suitable for the manufacture of industrial products ) are susceptible to this damage in varying degrees. Pigments in paints and stains protect against UV damage. For the drug referred to as "pigment" see Black tar heroin. UV-absorbers are added to polyurethane and other varnishes (e. g. spar varnish) to work against UV damage but are decreasingly effective over the course of 1-4 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. By contrast, wooden items retrieved from the Egyptian pyramids have a remarkably new and fresh appearance after 4000 years of storage. The Egyptian pyramids are pyramid shaped structures located in Egypt, and were built as a tomb for dead pharaohs Even there, however, fungal colonies were present, and mildew and fungus are another category of entities which attack varnish. In other words, the only coat of varnish with near perfect durability is the one stored in a vacuum, in darkness, at a low and unvarying temperature. Otherwise, care and upkeep are required.
Many modern polyurethanes have been formulated to overcome a variety of problems that plagued earlier polys.
Lacquer
The word lacquer refers to quick-drying, solvent-based varnishes or paints. In a general sense lacquer is a clear or coloured Varnish, that dries by solvent evaporation and often a curing process as well that produces a hard durable finish in any Although their names may be similarly derived, Lacquer is not the same as Shellac and is not dissolved in alcohol. Shellac is the commercial resin marketed in the form of amber flakes made from Lac, the secretion of the family of lac-producing insects though most commonly from the Lacquer is dissolved in Lacquer Thinner, which is a highly-flammable solvent. Lacquer is typically sprayed on, within a spray booth that evacuates overspray and minimizes the risk of combustion.
Outside America, 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 is a varnish. Thus the vast majority of wooden furniture is lacquered.
Acrylic
Acrylic varnishes are typically water-borne varnishes with the lowest refractive index (highest degree of clarity) of all finishes. In Organic chemistry, the acryl group is the Functional group with structure H 2 C =CH-C(= O)- it is the Acyl group The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium They impart little or no color. Acrylics have 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-levelling 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 the painting and the varnish, preferably a soft, glossy gel medium) to make varnish removal and overall conservation easier.
Two-Part
Various epoxies have been formulated as varnishes or floor finishes whereby two components are mixed directly before application. Often, the two parts are of equal volume and are referred to as "part A" and "part B". True polyurethanes are two-part systems. All two-part epoxies have a "pot-life" or "working time" during which the epoxy can be used. Usually the pot-life is a matter of a few hours but is also highly temperature dependent. Both water-borne and solvent based epoxies are used.
See also
- Desert varnish
- UV Coating - print finishing
- Tack cloth
References
- Bob Flexner (1993). Desert varnish, or rock varnish is a dark coating found on exposed rock surfaces in Arid environments The term "UV coating" has various meanings Ultra-violet coating of paper Ultra-violet cured coatings can be applied over ink printed on paper and dried by exposure Tack cloth is a sticky (or tacky material used for removing dust from a surface prior to finishing it with Paint, Varnish, or some similar product Understanding Wood Finishing: How to Select and Apply the Right Finish. Rodale Press: Emmaus, PA. ISBN 0-87596-566-0
External links
- The 17th century varnish of Lorenz Mizler
- Tung and Linseed Oils by Steven D. Russel
Dictionary
varnish
-noun
- A type of paint with a solvent that evaporates to leave a hard, transparent, glossy film.
- Anything resembling such a paint.
- By extension: A deceptively showy appearance.
-verb
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic