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Pointing, Paints and VarnishesUnit VIBCDProf S S JAHAGIRDARBE (CIVIL), ME(ENV.),PhD(persuing)NK Orchid college of Engg. and Tech. , SolapurPointingFinishing of mortar joints in masonry.In exposed masonry joints are weakest parts.Pointing consists of raking of joints to a depth of 10 to 20 mm.Types of pointing 1. Flush Pointing

Flush pointing The pointing may be level as in flush pointing, which is made by wiping over the finished pointing with the trowel or piece of rough cloth. Does not give good appearance.But it is durable as it does not provide any space for accumulation of dust, water etc 2. Keyed or grooved pointing

In this type mortar is first up flush with the face if wall. A semi circular notch is formed by a tool know as pointer. This type of pointing gives as attractive appearance to the surface. This type is mostly used for superior type work, particularly for vertical joints of walls.3.Recessed pointing

Recessed joints are not suitable for buildings in exposed situations.This is done by pressing mortar back from edges by 5 mm or more.Face of pointing is kept vertical.Only bricks with good frost resistance should be used with recessed joints.Gives good appearance.4. Weathered PointingV shaped projections are made.5. V pointing or bucket handle Formed by forming a V groove.

6. Beaded pointingFormed by steel or iron edge.Gives food appearance but liable to damage easily.7. Tuck pointing

Groove of 5 mm width and 3 mm depth is prepared.It is filled with white cement or putty.8. Struck pointing

Face of pointing is kept inclined Upper edge pressed inside face by 10 mm

Paints and varnishesPaintsPaints are used to protect metals, timber, or plastered surfaces from the corrosive effects of weather, heat, moisture or gases etc and to improve their appearance.

Properties of paintThere are a number of ways to judge paint quality:WearabilityCovering abilityEase of cleaningProtection of the substrateEnvironmentally Friendly AestheticPractical and Cost Effective

Composition of paintsFundamental components of an oil-based paint are:BodyVehiclePigmentThinnerDryer

Body Makes the paint film harder and more resistant to abrasionReduce shrinkage cracks on dryingIn white paint body is also the pigmentCommonly used bases (body) are White lead, Zinc oxide, Iron oxide, Metallic powder such as Al, Cu, Br. Paints more often named after the base as Lead paint, Zinc paint, and Aluminum paint.

The binder or resin, is the actual film forming component of paint. It imparts adhesion, binds the pigments together, and strongly influences such properties as gloss potential, exterior durability, flexibility, and toughness. VehicleOily liquid in which the body and pigment are solubleFacilitates the paint to be conveniently spread over the surfaceOils most commonly used as vehicle. The main purpose of the vehicle is to adjust the viscosity of the paint. It is volatile and does not become part of the paint film.It's main function is as the carrier for the non volatile components. Water is the main vehicle for water based paints.

PigmentPigments are materials which gives the paint its color. In white paint the body is the pigment. Natural pigments (natural iron oxides, chrome oxides). Synthetic pigments (phthalocynines coal tar derivatives)Pigments impart qualities such as color and opacity (sometimes inappropriately called 'hiding'), and influences properties such as gloss, film flow, and protective abilities.

ThinnerLiquid thinner is added in the paint toIncreases fluidityMaking paint more smoothHelp penetration into porous surfacesCommon thinner turpentine (made by distilling gum from a number of pine trees)

DryersAdded to quicken the drying of vehicleOrganic salts of Iron, zinc, lead, manganese, Ca To accelerate the oxidation and hardening of vehicle

Defects in paintingFading:The gradual loss of color is known as fading. This may be due to the effect of sun rays.Flaking or PeelingDue to the poor adhesion, paint may peel off from the surface.Blistering:This is caused by water vapour, which is trapped behind the painted surface. It may occur due to imperfect seasoning of timber.

FLAKING

BLISTERING

PEELINGBloomThe formation of dull patches on the finished surface is known as bloom. It may occur due to bad ventilation or defective paint.Running:The paint runs back and leaves some areas of surface un covered. This defect occurs when surface is too thickly painted sagging will occur.WrinklingIf the horizontal surface is too thickly painted wrinkling will occur.

WRINKLINGLACK OF ADHESION

FlashingThe patches seen on the painted surface is known as flashing. It may be due to poor workmanship, weather action, or poor quality of paint.Grining:If the opacity of the final coat is insufficient, the back ground of the painted surface is clearly visible, this is known as grinning.

EfflorescenceEfflorescence or formation of white powdery deposit on walls after painting is caused due to salts present in the building material like brick and mortar, which surface later on. The Solution- Give a long time gap between plastering and painting (about 6 months including one monsoon) Use paint with a porous film like emulsions and distempers.

EFFLORECENCEBrush marksBrush marks are caused due tounder-thinning of paints or due to poor application of the final coat of paint or due to poor quality brush. The Solution - Ensure paint of the right viscosity is applied using a good brush.

BRUSH MARKSVARNISHDefinition:A transparent solution of resinous substance in linseed oil, turpentine or in alcohol is called varnish.

VARNISHCharacteristics of a good varnishIt should dry rapidly.It should form a hard film on drying.It should not crack on drying.It should be durable and weather resistant.It should give uniform and pleasing appearance.It should not hide the natural grains of the inner surface of timber.

Painting the woodwork - StepsPreparation of surface:The new wood should be seasoned and it must be dried before painting. The surface of the wood should be cleaned and nails should be punched below the surface.

Knotting:The knots covered with suitable material is called knotting.

3. First coat:After knotting the primary coat is applied on the surface of the wood. It is usually applied before the wood work is fixed.4. Second coat:This coat is applied after knotting and priming coat. Each coat applied longitudinally in thin film and crossed, so that no brush mark is seen on this painted surface.5. Final coat:This coat is applied over the second coat without any brush mark.

Surface Preparation for Enamel painting Previously painted wooden surfaces must be properly sanded to remove any dust or grease. Apply wood primer by brush, after thinning to given ratio by recommended thinner.Allow it to dry for 6-8 hr then apply putty or Lambi Sand the applied putty with number 180 sand paper and then apply second coat of wood primer. Now the wooden surface is ready for painting with the top coat

Painting with enamelApply wood primer by brush, after thinning to given ratio by recommended thinner.Allow it to dry for 6-8 hr then apply putty or Lambi.Sand the applied putty with 180 no. sand paper and apply 2nd coat of wood primer. Now the wooden surface is ready for painting with the top coat

Enamels are normally applied by brushing although they can also be sprayed. The drying time of enamels is longer; hence care must be taken to ensure a dust free environment while the paint film is drying. Two coats of paint is sufficient in most cases, however if the earlier paint shade was significantly darker than the new shade an additional coat of paint is recommended.

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