Civil Engineering MaterialsCE-115byDr. S. Muhammad JamilSchool of Civil and Environment EngineeringNational University of Sciences and Technology, Islamabad

**Building MaterialsBuilding stonesBricks and clay productsCement concreteTimber and wood productsMetals and alloysPaints, varnishes, distempersAsphalt, bitumen and tarPlastics and fibersGlassInsulating MaterialsMiscellaneous Materials

**Paints and Varnishes

**DefinitionsPaint is a coating of fluid material applied over timber and metal surface as protective coating which on drying forms a thin film on surfacePaint is a mixture of liquid or medium and a coloring or pigment to impart color and provide protective coating to the surfaceOil based paints are polymers or pre-polymer solutions which form a film upon evaporation of the solventPaint is a dispersion of pigments in a drying oil, with addition of driers and thinners

**DefinitionsVarnish is a transparent or nearly transparent solution of resinous material and oil, alcohol or turpentine to form a clear, tough, matt or glossy protective film on woodwork.Enamel. Bases like zinc oxide ground in varnish. Dry quickly to furnish hard glossy finish.

**DefinitionsDistemper is a comparatively cheap decorative paint for walls and ceilings applied on brickwork, or plastered surfacesWater Wash and Color Wash. Fresh lime slacked with water, mixed thoroughly, screened and added with glue and may be a pigment

**DefinitionsFrench Polish. Type of spirit varnish prepared by dissolving resin in methylated spirit at room temperature for use on hardwood substances to hide grain defects.Wax Polish. Bees wax dissolved in turpentine used for highlighting the grain over wooden surfaces.

**Functions of PaintsTo protect the surface from weathering effects of the atmosphere and actions by other liquids, fumes and gasesTo provide pleasing, colorful and decorative appearance to the surfacesTo prevent decay of wooden membersTo prevent corrosion of metallic surfacesTo provide a smooth surface for easy cleaning

**Classification of Paints

**Classification of Paints

**Types of PaintsOil Paint: ordinary paintBituminous paint: prepared by dissolving asphalt or bitumen in oil or petroleumCement paint: It consists of cement and hydrated lime mixed along with a coloring pigmentColloidal paint: a paint with no inert materialAluminum paint: aluminum powder suspended in spirit varnish or oil varnishAsbestos paint:Cellulose paint: prepared from nitro cotton celluloid sheets

**Types of PaintsEmulsion paint: It consists of polyvinyl acetate and synthetic resin as binding materialEnamel paint: It consists of white lead ground in small quantity of oil and mixed with petroleum spirit and resinous matterGraphite paint:Luminous paint: contains calcium sulphide with varnishSilicate paint: prepared by mixing calcined ground silica with resinous substancesAnti-corrosive paint: consists of oil and strong drierPlastic paint: Synthetic rubber paint: prepared from resin

**Composition of Oil PaintsConstituents of oil paintsBaseVehicle an oil, generally linseed oilColoring pigment (s)Solvent or thinnerDrierInert fillerBy suitable variation of the type and proportion of various constituents the paints are made asDryGlossyflat

**Composition of Oil Paints - BaseBase : principal constituent, a solid matter forming the main body of paint and possessing binding properties.White lead, red lead, zinc oxide, iron oxide, metallic powders of aluminum, copper and bronze, etcMakes the paint film harder and more resistant to abrasionForms an opaque layer to obscure the surfaceReduces shrinkage cracks on drying

**Composition of Oil Paints - BaseWhite leadCheapest and most commonly used baseGreater covering power than all othersDense so good to obscure surfacesWeathers wellNot suitable for delicate works as gets discoloredNot suitable for painting of iron work due to rusting

**Composition of Oil Paints - BaseRed leadSticks well and protects against rusting. With oil considered best for first coat or prime coatGood drier for linseed oilLead paints are poisonous. Precautions needed while spraying or scrapping paint

**Composition of Oil Paints - BaseZinc oxide or Zinc whiteNot affected by weatherTakes a fine polish hence good for decoration worksNot poisonousLess durable and more costly than lead basedIron oxideUsed basically in finishing coat for iron workPrevents rust formationComparatively cheaperTints vary from yellowish brown to black

**Composition of Oil Paints - VehicleVehicle: Carrier liquid which carries solid materials of base and helps them to spread evenly on the surface to be painted. Linseed oil, poppy oil, nut oil, soyabean oil, castor oil, fish oil, latex emulsionsOily liquid in which base and pigment are solubleFacilitates the paint to be conveniently spread evenly over the surfaceActs as a binder for the base and causes it to stick to the surfaceOn drying forms a tough and elastic film

**Composition of Oil Paints - VehicleRaw linseed oilThin, pale and transparent oilSweet taste, no smellBecomes hard and stiff on exposure to airWhen spread in thin film, looks like varnishDries very slowlyUsed for painting delicate interior work and wood work

**Composition of Oil Paints - VehicleBoiled linseed oilThicker and darker in color (deep amber to rich brown)Dries quickly. On drying leaves a hard, glossy and durable surfaceHas more area coverage capacityUsed for exterior workDouble boiled linseed oilLight in color as raw linseed oil but with different smellDries quicker and gives better resultsRequires and thinning agent like turpentine oil

**Composition of Oil Paints - PigmentColoring pigments: finely divided solid coloring matter to provide shade, color and capacity to paintBlacks: lamp black, vegetable black, ivory blackBlues: indigo, Prussian blueYellows: chrome yellow, raw Siena, yellow ochreGreens: copper sulphateBrowns: raw umber, burnt umberRed: red lead, vermillion, carmine

**Composition of Oil Paints - ThinnerSolvent or thinner: A volatile liquid added to prepare paint to increase fluidity thus workability and ease of applicationThinner helps penetration of paint in porous surfacesTurpentine oil is most common thinnerExcessive thinner dulls the colors and glossExcessive thinner reduces protective value of paint

**Composition of Oil Paints - DrierDrier: added to paint to quicken the drying of vehicleLinseed oil dries by absorbing oxygenDrying process expedited by adding oxygen rich substancesCommon driers are: Litharge, Red lead, Lead acetate, Manganese dioxide, Zinc sulphateExcessive drier destroys the elasticity of paint and causes flakingDrier is added to the paint just before use

**Composition of Oil Paints - FillerInert fillerAn adulterant mixed to replace the base in part thus reducing the cost of paintCommonly used fillers are silica, charcoal, powdered chalk, aluminum silicate, barium sulphate, etc

**Characteristics of Good PaintsShould have a good body or spreading powerShould work smoothly and freely to be laid in thin coatShould form durable, tough and wear resistant film upon dryingColor should not fade or changePainted surface should dry in about 9 hoursShould become hard enough in 24 hours to take up another coatShould not crack upon dryingShould give a smooth and pleasing finishShould dry quicklyShould not damage the painted surface

**Manufacture of Oil PaintsThe base (white lead) is thoroughly ground in oilThinner (turpentine oil) is mixed to give it necessary workabilityPigment and drier are separately ground in linseed oil and mixed with turpentine oil to make it thinPigment mixture intimately mixed with already prepared base Prepared paint is strained through fine cloth or sieve

**Manufacture of Oil Paints

**Defects in PaintingCracking: cracks extending throughout the entire thickness of paint, due toImproper seasoning of woodExcessive use of drierApplication of too many coatsCrazing and crocodiling: Hairline cracks in top coat, due toUse of excessive oilUse of impure oilInsufficient drying of under coat

**Defects in PaintingBlistering and peeling:Exposure of paint to strong sunshineLeaving oil or grease on the surface to be paintedPainting a surface with moisture on surface or in pores of woodRuns and sage:Application of too thick or slow drying paintPainting over a glossy surfaceUse of excessive drierExcessive humidity or rapid thermal changes during drying period

**Defects in PaintingChalking: rub off with hands or clothesUse of insufficient oil in priming coatWashing off: deposition of water soluble dissolved matter at lower edges forming streaksDull appearance: caused by use of excessive drier or on aging

**Defects in PaintingSlow drying: use of inferior or old oilsPainting over damp surfacesPainting during unfavorable weatherYellowing of white paint:Use white enamel where gloss is desiredFor indoors use linseed oil with yellow tint that does not bleach unless exposed to sunshine

**LINSEED OIL

**Brown OchreOchreorOcher(pronounced/okr/OH-kr, from theGreek,khrs, pale) is term for both agolden-yellowor light yellowbrowncolor and for a form of earthpigmentwhich produces the color.

**VARIOUS PIGMENTS