Lesson Notes By Weeks and Term v3 - Senior Secondary 2
Wood finishes and finishing
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Wood finishes and finishing
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Subject: Wood-Work
Class: Senior Secondary 2
Term: 1st Term
Week: 7
Theme: Design And Construction
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Identify and state the uses of different wood finishes Name the to ols, equipment and materials for applying finishes State properties of wood finishes Prepare surfaces for wood finishing Apply finishes to wood surfaces
Equipment, and Materials for Applying Finishes (Objective 2)
Application Tools: Brushes: Various sizes and types (natural bristles for oil-based, synthetic for water-based) for precise application.
Rollers: For large, flat surfaces, ensuring even application (foam rollers for smooth finishes, nap rollers for textured).
Spray Guns: For professional, smooth, and even application, especially for lacquer and polyurethane. Requires an air compressor, spray gun, and appropriate nozzles.
Wiping Cloths/Pads: For oil finishes, stains, and waxes. Lint-free cloths are essential.
Applicator Pads: Special pads for applying certain clear finishes.
Surface Preparation Tools & Materials: Sandpaper: Various grits (e.g., 80, 120, 180, 220, 320, 400) for progressive sanding.
Sanding Blocks/Pads: For manual sanding.
Orbital Sanders/Belt Sanders: For mechanical sanding of large surfaces.
Wood Fillers/Putty: For filling holes, cracks, and imperfections.
Scrapers: For removing old finishes or stubborn imperfections.
Steel Wool: For specific finishing steps or rubbing out finishes.
Tack Cloths/Dusting Brushes: For removing dust particles before finishing.
Solvents/Thinners: For cleaning brushes, thinning finishes, or degreasing surfaces (e.g., mineral spirits, lacquer thinner, turpentine). Safety Equipment (PPE - Personal Protective Equipment): Respirators/Dust Masks: To protect against inhaling sanding dust and chemical fumes from finishes.
Safety Goggles/Glasses: To protect eyes from splashes or dust.
Gloves: To protect hands from finishes and solvents.
Ventilation: Ensure adequate airflow in the workspace. 2.
4. Properties of Wood Finishes (Objective 3)
Durability: The finish's ability to resist scratches, abrasions, impacts, and general wear. Polyurethane and lacquer are generally highly durable.
Water Resistance: The finish's ability to repel water and prevent moisture penetration into the wood. Varnishes and paints offer good water resistance.
UV Resistance: The ability to withstand degradation from ultraviolet light, which can cause discolouration or breakdown of the finish, especially for outdoor applications.
Drying Time: The time it takes for a finish to become tack-free or ready for the next coat. Lacquers dry very quickly, while oil-based varnishes dry slower.
Ease of Application: How easy it is to apply the finish evenly and smoothly without drips or brush marks. Wiping varnishes and oils are generally easier to apply for beginners.
Adhesion: How well the finish sticks to the wood surface. Proper surface preparation is crucial for good adhesion.
Aesthetic Qualities: Gloss Level: Ranges from high gloss (very shiny) to semi-gloss, satin, and matte (dull, non-reflective).
Colour: Whether the finish is clear, tinted, or opaque (paint).
Clarity: How transparent the finish is, allowing the wood grain to show through.
Flexibility: The finish's ability to flex with the natural movement of wood (expansion/contraction) without cracking.
Chemical Resistance: Resistance to household chemicals, alcohol, and cleaning agents.
Heat Resistance: The ability of the finish to withstand moderate heat without blistering or discolouring. 2.
5. Preparing Surfaces for Wood Finishing (Objective 4) Thorough surface preparation is paramount for a high-quality finish.
Stages:
1. Initial Cleaning and Inspection: Remove all dirt, grease, old finishes (if refinishing), and any foreign matter. Inspect the wood for defects like scratches, dents, gouges, or glue residue.
2. Filling and Repairing: Fill all nail holes, screw holes, and minor cracks with a suitable wood filler or putty that matches the wood species or intended stain colour. Allow to dry completely. For larger defects, use wood patches or epoxy fillers.
3. Sanding: This is a crucial, multi-stage process.
Coarse Sanding: Start with a relatively coarse grit sandpaper (e.g., P80 or P100) to remove planer marks, saw marks, and initial imperfections. Sand with the grain.
Medium Sanding: Progress to finer grits (e.g., P120, then P150) to remove scratches left by the previous coarser grit. Continue sanding with the grain.
Fine Sanding: Finish with fine grits (e.g., P180, P220) for most clear finishes, or even P320-P400 for high-gloss, ultra-smooth finishes. Each finer grit removes the sanding marks of the previous grit, creating a progressively smoother surface.
Important: Always sand with the grain to avoid unsightly cross-grain scratches. Ensure all previous sanding marks are removed before moving to the next grit.
4. Dust Removal:** After the final 2.
1. Definition and Purpose of Wood Finishes A wood finish is a substance applied to the surface of a wooden object.
Its primary purposes are: Protection: To shield the wood from moisture, dirt, chemicals, ultraviolet (UV) radiation, insects (like termites and wood borers), and general wear and tear. This prevents warping, cracking, staining, and decay.
Enhancement of Appearance: To bring out the natural beauty of the wood grain, add colour, create gloss or matte effects, and generally improve the aesthetic appeal of the product.
Smoothness: To create a smooth, tactile surface that is pleasant to touch and easy to clean.
Durability: To increase the resistance of the wood to scratches, abrasions, and impacts. 2.
2. Types of Wood Finishes and Their Uses (Objective 1) | S/N | Type of Finish | Description & Key Characteristics | Typical Uses in Nigeria | | :-- | :------------- | :--------------------------------------------------------------------------------------------------------------------------------------- | :----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | 1. | Varnish | A clear or slightly amber-tinted coating that hardens to a durable, transparent film. Available in gloss, semi-gloss, and matte. Resistant to water and abrasion. Types include Oil Varnish, Spirit Varnish, Polyurethane Varnish. | Most common for indoor and outdoor furniture (tables, chairs, cabinets), doors, window frames, wooden floors, wall paneling. Chosen for its durability and protective qualities against moisture and scratches. Widely used in homes and offices. | | 2. | Lacquer | A clear, fast-drying finish that creates a hard, durable, and highly protective film. Often applied by spraying. Can be clear or pigmented. | Furniture (especially those requiring a smooth, tough finish like dining tables, cabinet doors), musical instruments (guitars, drums), wooden crafts, and decorative items. Popular in modern furniture workshops due to fast drying time, allowing quicker production cycles. | | 3. | Paint | An opaque coating that provides colour and protection, completely obscuring the wood grain. Available in various types (oil-based, water-based/emulsion). Provides excellent weather resistance. | Outdoor furniture (garden benches), play equipment, wooden gates, fascia boards, and decorative interior elements where a specific colour scheme is desired. Also used on cheaper timber to give an aesthetic upgrade or protect against elements, especially in areas with high rainfall and humidity. | | 4. | Stain | A liquid containing dyes or pigments designed to change the colour of wood without obscuring its natural grain. Penetrates the wood surface. | Used to mimic the appearance of expensive timber on cheaper wood, or to achieve a specific aesthetic effect on furniture, carvings, and wooden crafts. Common for enhancing the grain of Iroko, Mahogany, or creating antique looks. Often followed by a clear topcoat (varnish, lacquer) for protection. | | 5. | Polish | Often a combination of wax (e.g., beeswax, carnauba wax) and solvents. Provides a soft sheen, enhances the natural feel of the wood, and offers mild protection. Shellac is a traditional polish. | Traditional or antique furniture, wooden carvings, decorative items where a natural, soft luster is desired. Shellac is particularly used for French polishing and sealing purposes. Wax polishes are also used for maintaining finished surfaces, offering a renewable protective layer. | | 6. | Oil Finishes | Penetrating finishes (e.g., Linseed oil, Tung oil, Danish oil) that soak into the wood rather than forming a film on the surface. Enhance the natural grain and provide a warm, soft look. Easily repaired. | Kitchen countertops, cutting boards, wooden bowls, tool handles, and furniture where a natural, tactile feel is preferred. Often chosen for items that might come into contact with food or where minor scratches can be easily blended in. Requires regular re-application. | 2.
3. Tools, Equipment, and Materials for Applying Finishes (Objective 2)
Application Tools: Brushes: Various sizes and types (natural bristles for oil-based, synthetic for water-based) for precise application.
Rollers: For large, flat surfaces, ensuring even application (foam rollers for smooth finishes, nap rollers for textured).
Spray Guns: For professional, smooth, and even application, especially for lacquer and polyurethane. Requires an air compressor, spray gun, and appropriate nozzles.
Wiping Cloths/Pads: For oil finishes, stains, and waxes. Lint-free cloths are essential.
Applicator Pads: Special pads for applying certain clear finishes. * Sanding: Progress to finer grits (e.g., P120, then P150) to remove scratches left by the previous coarser grit. Continue sanding with the grain.
Fine Sanding: Finish with fine grits (e.g., P180, P220) for most clear finishes, or even P320-P400 for high-gloss, ultra-smooth finishes. Each finer grit removes the sanding marks of the previous grit, creating a progressively smoother surface.
Important: Always sand with the grain to avoid unsightly cross-grain scratches. Ensure all previous sanding marks are removed before moving to the next grit.
4. Dust Removal: After the final sanding, thoroughly remove all sanding dust using a stiff brush, vacuum cleaner, or compressed air. Wipe the surface with a tack cloth (a sticky cloth designed to pick up fine dust) or a clean cloth dampened with mineral spirits (for oil-based finishes) or water (for water-based finishes).
5. Conditioning/Sealing (Optional but Recommended): For softwoods or woods with inconsistent grain absorption (e.g., pine, birch), apply a wood conditioner to ensure even stain absorption and prevent blotching. Apply a sanding sealer as a first coat for clear finishes. This seals the wood pores, raises the grain slightly (which can then be lightly sanded smooth), and provides a uniform base for subsequent finish coats. 2.
6. Applying Finishes to Wood Surfaces (Objective 5) General principles apply to most finishes, but specific techniques vary.
1. Read Manufacturer's Instructions: Always follow the specific instructions on the product label regarding application, drying times, thinning, and safety.
2. Ventilation and Safety: Work in a well-ventilated area. Wear appropriate PPE (respirator, gloves, safety glasses).
3. Mixing: Stir finishes thoroughly before and during use to ensure even dispersion of solids. Do not shake, as this can create air bubbles.
4. First Coat (Sealer/Primer/Thinned Coat): If using a sealer, apply it evenly. Lightly sand with a very fine grit (P320-P400) after drying to smooth out the raised grain, then clean thoroughly. For some finishes (e.g., varnish), the first coat can be thinned slightly to improve penetration and adhesion.
5. Application Technique: Brushing: Dip the brush about one-third into the finish. Apply in long, even strokes, working with the grain. Avoid overworking the finish, as this can lead to brush marks and air bubbles. Feather out the edges to avoid overlap marks. Work on one section at a time.
Rolling: Use a suitable roller cover (e.g., foam for smooth finishes). Apply in even passes, overlapping slightly to ensure full coverage. Follow with a light brush stroke (tipping off) if necessary to smooth out roller marks.
Spraying: Maintain a consistent distance (typically 6-10 inches) from the surface. Use consistent, overlapping passes (about 50%) to ensure even coverage. Move the gun parallel to the surface at a steady speed. Practice on scrap wood first to get the right technique and settings.
Wiping (for oils/stains): Apply generously with a lint-free cloth or brush. Allow to penetrate for the recommended time (e.g., 5-15 minutes). Wipe off excess thoroughly with a clean, dry, lint-free cloth. Failure to wipe off excess can result in a sticky, uneven finish.
6. Drying Between Coats: Allow each coat to dry completely according to manufacturer instructions. Applying too soon can lead to adhesion problems, bubbling, or a soft finish.
7. Sanding Between Coats (for film-building finishes): Lightly sand between coats with a fine grit sandpaper (e.g., P220-P320) to ensure good adhesion for the next coat and to remove any dust nibs or imperfections. Clean off all sanding dust before applying the next coat.
8. Final Coat and Curing: Apply the final coat and allow it to cure fully. Curing time is often much longer than drying time (can be days or weeks, depending on the finish type). Avoid heavy use during the curing period.
Example: Finishing a Plywood Cabinet Door with Varnish
1. Prepare the door:** Ensure the door is clean and free of sawdust or glue. Fill any small holes (e.g., from nails) with wood filler and allow to dry. * Sand the entire door, starting with P120 grit, then P180, and Final Coat and Curing: Apply the final coat and allow it to cure fully. Curing time is often much longer than drying time (can be days or weeks, depending on the finish type). Avoid heavy use during the curing period.
Example: Finishing a Plywood Cabinet Door with Varnish
1. Prepare the door: Ensure the door is clean and free of sawdust or glue. Fill any small holes (e.g., from nails) with wood filler and allow to dry. Sand the entire door, starting with P120 grit, then P180, and finally P220, always sanding with the grain. Thoroughly clean off all sanding dust with a tack cloth.
2. Apply Sanding Sealer (Optional but recommended): Apply a thin, even coat of sanding sealer with a brush. Allow to dry completely (check manufacturer's instructions). Lightly sand with P320 grit to knock down raised grain, then clean dust.
3. Apply Varnish: Stir the varnish well. Using a good quality brush, apply a thin, even coat of varnish, working with the grain. Avoid drips and sags. Allow to dry completely (e.g., 6-8 hours). Lightly sand with P220-P320 grit to de-nib and improve adhesion for the next coat. Clean off dust.
4. Repeat Varnish Application: * Apply a second, and if desired, a third coat of varnish, following the same drying and light sanding steps between coats.
5. Final Curing: Allow the final coat to cure for several days or weeks before heavy use to achieve maximum durability.
Entrepreneurship and Skill Development: Many young Nigerians are engaged in carpentry, furniture making, and craft work. Mastering wood finishing techniques directly equips them with a valuable skill for self-employment or employment in the informal and formal sectors. This includes furniture production, wooden door and window fabrication, and creating decorative wooden items (e.g., carved masks, stools, trays) for local consumption and export, enhancing their market value and durability.
Home Maintenance and Preservation: Understanding wood finishes allows individuals to properly maintain and protect wooden assets in their homes, such as doors, windows, roof trusses, and furniture, from the effects of the tropical climate (humidity, rain, sun) and pests (termites). This knowledge helps in making informed decisions when renovating or repairing, leading to cost savings and extended lifespan of wooden structures.
Environmental and Health Awareness: The use of certain finishes and solvents can have environmental and health implications. This topic can integrate discussions on using eco-friendly, low-VOC (Volatile Organic Compounds) finishes available in Nigeria, proper disposal of waste materials (e.g., used solvents, finish containers), and the importance of ventilation and PPE, fostering responsible practices among future woodworkers. This aligns with broader national efforts for sustainable development and public health.