Interior Wall Painting Honor

Vocational Activities

Requirements

  1. Explain how to prepare wood to receive varnish.

    Answer: Sand progressively (80, 120, 220), remove the dust, apply a pore-filling sealer, re-sand with 320, and then apply varnish with a soft brush in thin coats at an interval of 4-6h. — Unprepared wood absorbs varnish unevenly and becomes blotchy. Progressive sandpaper eliminates previous marks. The sealer saves varnish and evens out. Traditional varnish is polyurethane-based (more resistant) or nitrocellulose. Marine varnish resists moisture. Always work with PPE and a ventilated area.

  2. Explain and demonstrate how to prepare and finish wood using the following techniques:
    • Bleaching (lightening)
    • Varnish
    • Painting

    Answer: 1) Bleaching: apply 30-volume hydrogen peroxide or oxalic acid over the already-sanded wood, let it act for about 20 min, neutralize with vinegar (or a solution of water and baking soda), rinse, and let it dry well before proceeding. It serves to even out the tone and remove stains. 2) Varnish: sand the wood progressively (80 → 220), remove the dust, apply a sealer/primer, and give 2 coats of varnish, sanding lightly between coats for a smooth, protective finish. 3) Painting: sand the surface, apply a primer-sealer suitable for wood and, after it dries, give 2 coats of synthetic enamel or acrylic paint, sanding lightly between coats for good adhesion and a uniform finish. — Bleaching removes dark stains in old wood. Oxalic acid (white crystals) is milder than peroxide. Polyurethane varnish is more resistant than nitrocellulose. Synthetic enamel has superior coverage. Always use PPE: goggles, nitrile gloves, and a mask against fumes in a ventilated environment.

  3. Mention 2 methods of creating texture on walls.

    Answer: A textured foam roller with relief creates an orange-peel effect. Textured compound (graffiato) applied with a trowel and finished with a roller, sponge, or brush gives a rustic effect. — Suvinil, Coral, and Sherwin-Williams have specific lines: 'Texturatto', 'Coralcrim'. Graffiato gives a classic scratched effect. Roughcast (chapisco) is more rustic. Fine compound + sponge simulates travertine. Always apply over an acrylic sealer on a crack-free wall. Work while wet so as not to leave seams.

  4. In what situation should a paint gun (spray gun) be used, and know how to set the correct pressure for painting.

    Answer: Use it on large, irregular surfaces or those with many details (paneled doors, furniture). HVLP pressure: 30-40 psi (2-3 bar), distance 20-25 cm from the surface, nozzle 1.4-1.8 mm for enamels. Parallel movements overlapping 50% without stopping at the ends. — HVLP (High Volume Low Pressure) has ~70% paint transfer efficiency vs. ~40% for the conventional spray gun. The paint must be thinned according to the nozzle (a viscosity cup measures it). Spraying requires a booth or an isolated area with a plastic curtain. PPE is mandatory: an organic-filter mask, sealed goggles, a coverall.

  5. Describe the proper methods of cleaning and caring for paint and varnish brushes.

    Answer: Latex/PVA: water and soap while still wet. Enamel/oil/varnish: mineral spirits. Comb the bristles, dry, and hang with the bristles up. Never soak it for hours — it warps. — Natural-bristle brushes (hog) for oil; synthetic ones (polyester, nylon) for latex. Mineral spirits is a petroleum distillate; thinner is a more aggressive mixture. A good brush costs R$30-200 and lasts for years with care. Incomplete washing hardens it and leads to discarding it.

  6. Demonstrate how to correctly use wall filler (joint compound).

    Answer: Apply with a trowel in thin layers (1-2 mm), in crossed horizontal and vertical movements. Wait for it to dry (4-6h), sand with 220 grit, and remove the dust with a damp cloth. Repeat until level. Use only in dry indoor environments — drywall joint compound dissolves with water. — Drywall joint compound is PVA + mineral filler; acrylic compound resists moisture. A layer >3mm cracks as it dries. On joints use drywall mesh tape. 220 grit for a smooth finish, 320 for super smooth. Do not use it in a bathroom or outdoor area — for these, acrylic compound is the correct one.

  7. Explain the difference between paints for exterior and interior painting.

    Answer: Exterior: resists UV, rain, fungi, and sea air (acrylic facade paint, with anti-mold additives). Interior: focus on coverage, washability, and low VOC emission (PVA latex, enamel for wood). Exterior is more expensive and resistant; interior is more washable and economical. — Exterior Coralit/Suvinil Fachada uses acrylic resins + water-repellent additives. VOC = volatile organic compounds; premium paints have 'low VOC' or 'zero VOC' (Eucatex, Sherwin Harmony). CONAMA Resolution 491/2018 limits VOC. Painting indoors with exterior paint heats up the environment.

  8. Make a list of 10 color combinations for interior painting, using the color chart of a well-known brand. Why are strong colors not advisable?

    Answer: Ten color combinations for interiors (based on the fan decks of brands like Suvinil/Coral): 1) White with serene blue; 2) Beige with coffee brown; 3) Light gray with moss green; 4) Off-white with terracotta; 5) Sand with caramel; 6) Lilac with lavender; 7) Salmon with cream; 8) Mint green with white; 9) Ice with graphite; 10) Peach with snow white. Strong colors are not advisable in interiors because they tire the eyes, make the room feel heavy and visually smaller, are harder to combine with furniture, and show dirt/application flaws more. — Suvinil, Coral, and Sherwin have a 'Decora' app to combine. The 60-30-10 rule: dominant 60%, secondary 30%, accent 10%. Cool colors enlarge, warm ones make cozy. Pantone 2024 'Peach Fuzz' applied as an accent. Highly saturated colors (bright red, fluorescent orange) reflect onto nearby walls, creating an irritating 'indirect paint'.

  9. Explain the composition of the following paints and in what situations they should be used:
    • Glossy paint
    • Matte paint
    • Water-soluble paint

    Answer: 1) Glossy paint: composed of alkyd resins or polyurethane; results in a glossy, washable, and resistant finish. Used in humid and high-use environments, such as the bathroom and kitchen, and on surfaces that need to be cleaned frequently. 2) Matte paint: has a matte finish (without gloss); it conceals flaws and imperfections of the wall. Used on ceilings and bedrooms, where a soft, reflection-free look is desired. 3) Water-soluble paint: PVA- or acrylic-based, dilutable in water, non-toxic, and quick-drying. Used in interior environments in general, because it is easy to apply and low-odor. — 'Satin' gloss has 30-50% reflection; semi-gloss 50-70%; high gloss 70%+. Matte <10% reflection. Oil paint (alkyd) needs a solvent (mineral spirits); water paint (PVA) cleans with water — hence 'water-soluble'. PVA is most used on ceilings; acrylic is better on walls because of its washability.

  10. Paint the wooden parts of at least 4 rooms.

    Answer: Select 4 rooms; identify the wood (door, window, baseboard, built-in furniture); prepare it (sand, primer); apply 2 coats with a 4-6h interval; paint from top to bottom; mask off with masking tape and plastic; document with before/after photos. — Each room uses ~150 ml of paint for doors and baseboards. Synthetic enamel (premium) covers in 2 coats; economical needs 3. Painting from top to bottom avoids drips. Mask doorknobs with painter's tape. Work with the windows open and ventilation to reduce the VOC inhaled during application.

  11. Paint at least 1 entire room.

    Answer: Empty the room, protect with a tarp, sand, joint compound, sealer. Apply 2 coats with a roller and brush, starting from the ceiling and going down. Wait 24h between coats with the window open. — Professional sequence: ceiling → walls → windows/doors → baseboards. A foam roller for latex; a high-pile wool roller for textures. Work in a 'W' (up-and-down) and finish with a vertical pass without reloading. A 12 m² room uses ~3L of paint for 2 coats. Keep the windows open for 48h after finishing to cure.

  12. What is the difference between wall filler and fine lime?

    Answer: Drywall joint compound: PVA + mineral filler; for indoor use in a dry environment; levels walls; easy to sand. Fine lime (lime putty): hydrated lime + filler; resists moisture; used in outdoor areas and humid environments. Joint compound dissolves with water; fine lime does not. — Joint compound costs about 30% less than fine lime but is restricted to dry interiors. Fine lime contains CH-I lime (NBR 7175). For bathrooms and kitchens, acrylic compound (intermediate) is used. Cure time: joint compound 4-6h per coat; fine lime 12-24h per coat because of the chemical reaction.

  13. Know the correct ratio for diluting the following types of paint:
    • Latex or PVA
    • Acrylic
    • Enamel
    • Varnish
    • Oil
    • Epoxy

    Answer: 1) Latex or PVA: thin with 20-30% water. 2) Acrylic: thin with 10-20% water. 3) Enamel (synthetic): thin with 10-15% mineral spirits (solvent). 4) Varnish: thin with 10-15% mineral spirits for the first coat (subsequent coats thicker, as per the manufacturer). 5) Oil: thin with 10-20% mineral spirits. 6) Epoxy: do not use water or solvent to thin; mix the two components (A + B) in the proportion indicated by the manufacturer, usually 4:1. — Thinning incorrectly causes running or poor adhesion. The paint on the label already comes 'ready to use' but with a roller the 1st coat needs more thinning. Epoxy has a catalyst (hardener) — once mixed, the pot life is ~30 min. Mineral spirits is less aggressive than thinner; always test compatibility first.

  14. Know what precautions to take and the PPE necessary to work with interior painting.

    Answer: PPE: a mask with an organic filter, sealed goggles, nitrile gloves, closed shoes, a coverall. Precautions: ventilation, empty the room, protect the floor, do not eat in the area, dispose of cans at a recycling drop-off point. — VOCs (volatile organic compounds) from paints cause headaches, irritation of the respiratory tract, and in the long term liver problems. CONAMA Resolution 491/2018 limits VOC. A surgical mask does NOT protect — a chemical filter is needed. Children and pregnant women should avoid the painted area for 48h after finishing.