Lecture 6 - Paint & Coatings

Māori architecture:
- Pigments: $\text{red}$ , $\text{black}$ , $\text{blue}$ , $\text{white}$ —all derived from natural minerals, plants or clays.
- Natural binders (“sizes”) & extenders were mixed to improve brightness, viscosity or coverage.
Western precedents:
- Whitewash & wood stain (decorative + protective).
- Examples: $14^{th}$ -century Spanish hall, $16^{th}$ -century English townhouse.
- Gilding used to highlight architectural elements.
European cities display a “natural palette” driven by locally quarried stone, brick or timber.
Early New Zealand:
- Stone, slate, timber.
- Timber was routinely painted to resist rot; Wellington nicknamed the “Painted Town” (e.g.a0colourful houses along $\text{Tinakori Rd}$ ).

Base material & inherent properties
- Dimensional stability, expansion/contraction, porosity, reaction to UV/moisture.
Surface condition & preparation
- Cleaning, filling, sanding, de-contamination.
Coating system
- Primer ➔ undercoat ➔ top-coat / clear-coat / texture, etc.
Environment & exposure
- Interior vs exterior, humidity, marine, abrasion, chemicals.
Stakeholders
- Designer/specifier, applicator/contractor, owner, end-user.

Mild steel: galvanising, $\text{zinc-alume}$ , paint, baked enamel, powder-coat, chrome.
Brass: chrome, satin chrome, black chrome, BMA (black matte anodised), lacquer.
Aluminium: anodising, powder-coating, wet-spray lacquer (limitations on adhesion & UV stability).
Manufacturing note: Powder-coat = electro-statically charged powder baked onto substrate (modern “enamel”).

Solid timber finishes (historic ➔ modern):
- French polish (shellac), oils, wax, varnish, polyurethane (high VOC), hard-wax oils, stains, paint.
Particle-board / MDF:
- Paint is straightforward.
- Clear/stain require special sealer because board contains waxes & $\text{formaldehyde}$ ➔ uneven absorption if unsealed.

Concrete, plaster & fibre-boards: paint or specialist textured coatings (consult manufacturer).
GIB (drywall):
- Option $1$ —fasten, stop, seal/prime, paint.
- Option $2$ —lining paper (texture or anaglypta) then paint/wallpaper.

Acrylic (water-based)
- Exterior weatherboards, concrete/plaster; interior walls & ceilings.
Acrylic enamel (e.g.a0Resene Enamacryl)
- Water-borne but cures to hard enamel-like film—used where durability + quick dry = priority.
Alkyd enamel (synthetic “oil”)
- Tougher, slower dry; kitchen/bath joinery, exterior doors, skirtings.
Traditional oil-based linseed formulations
- Still available; longest drying, highest gloss, strong odour.

Oils: teak oil, tung oil—enhance grain, periodic re-coat.
Polyurethanes:
- Solvent-borne (amber over time, high VOC).
- Moisture-cure: hardest film, very long off-gassing.
- Water-borne acrylic PU: low VOC, non-yellowing, may need wax over-coat for floors.
Hard-wax oils: new hybrid giving tougher surface with natural look.

Mineral silicate paints, limewash, anti-graffiti, marine epoxies, speckle/stone, automotive two-pack lacquers, waterproofing membranes (fibreglass, liquid-applied roof systems).
Limewash: Porters (imported Italian) forms protective calcite crust; aesthetically ages (white “blooms”).

Industry palettes:
- $02/1960$ (NZ standard, circa $1950$ s).
- $BS\,5252$ (British Standard $5252$ ).
Proprietary fan-decks (Resene, Dulux) + designer ranges (e.g.a0Karen Walker) have custom codes.
Always request a brush-out (large hand-painted swatch) and test on actual substrate under multiple lighting conditions.
Computer tinting ≠ foolproof: UV ageing means touch-ups after $\approx$ $10$ years rarely match.

Dark colours ➔ absorb heat; light ➔ reflect.
- Dark paint on unstable timber may cause warping/twisting.
Substrate porosity: concrete will "drink" paint—may take extra coats to match fibre-cement panel beside it.

Gloss = more binder/less pigment
- Hard, washable, dirt-resistant; unforgiving of surface defects; ideal for windowsills, joinery, kitchens.
Flat/Matt = less binder/more pigment
- Hides imperfections; susceptible to burnishing; good for ceilings & low-wear walls.
Semi-gloss, satin & low-sheen fill the performance/appearance spectrum in between.

Historic toxins:
- Lead paint in buildings pre- $1980$ ; asbestos in certain boards/coatings—OK if sealed outside but must be professionally removed inside.
Personal Protective Equipment (PPE): gloves, goggles, long sleeves, rated respirator (NOT a simple paper dust mask).
Chemical hazards:
- Solvents = flammable + suspected carcinogen; strong odour is a warning.
- Oil-soaked rags can spontaneously combust—always hang flat to dry before disposal.
- Isocyanates (two-pack PU, automotive lacquers) = highly toxic to lungs/skin/eyes.
- Paint strippers—even citrus-based—can burn skin; wear PPE.
- Metal pre-treatment acids/alkalis burn tissue.
- Dust (especially concrete & asbestos) = respiratory hazard.

Old method: generic notes (“All doors: enamel paint; All walls: acrylic”).
Current best practice: product-specific, manufacturer-backed system for performance warranty.
- Large firms often insist on certified applicators.
Small jobs may still use generic spec but include colour code & sheen.
Typical schedule fields: substrate ➔ prep steps ➔ primer ➔ undercoat ➔ top-coat (# of coats, brand, product, colour, sheen) ➔ coverage rate (e.g.a0 $10 \text{m}^2/\ell$ ).
Finishes keyed on drawings (plans, elevations, reflected ceiling) via triangles, tags, or alphanumeric codes.

Rapid shift toward water-borne technology (acrylic enamels) for faster turnaround & lower VOCs while approaching oil-paint flow/outcome.
Digital tools: Resene Colour Vision, Dulux Colour Easy allow on-screen testing and palette export to BIM.
Minimal-finish design: exposing raw timber/concrete to maintain material honesty, reduce cost & embodied energy.
Heritage/patina argument: each repaint erases historic surface stories.