Interior painting is a fundamental finishing process in interior design that shapes the aesthetic and functional qualities of interior spaces. For Kenyan interior design professionals, mastering the selection and application of paints ensures that spaces not only meet client expectations but also comply with environmental and durability standards. This chapter introduces the essential knowledge about paints, their types, properties, and how they influence the overall interior design outcome. Understanding paints deeply aids in making informed decisions that enhance the durability, appearance, and maintenance of interior finishes.

5.1 Introduction to paints.

Paint is a liquid or paste coating that is applied to a surface in a thin layer and dries to form a solid, continuous film that protects and decorates the surface. It is the most widely used interior finish because it is relatively cheap, quick to apply, available in almost any colour and easy to renew. In interior design, paint is used not only to colour walls, ceilings, doors and furniture but also to protect them from moisture, stains and wear, to improve hygiene and to reflect light. Example: when a private hospital refurbished its wards, the designer specified a washable, mould-resistant paint so that walls could be cleaned daily while giving the rooms a calm, light colour.

Functions of paint

• Protection: Shields surfaces from moisture, dirt, corrosion, insects and wear.
• Decoration: Adds colour and finish, changing the mood and character of a space.
• Hygiene: Gives smooth, washable surfaces that resist dirt and bacteria.
• Light reflection: Light colours reflect daylight and artificial light, making rooms brighter.
• Identification: Colours mark zones, safety areas, services and directions.
• Concealment: Hides minor defects and joins and gives a uniform appearance.

Composition of paint

Every paint is a mixture of a few basic ingredients, and the proportions of these decide how it performs.

• Pigment: Fine powder that gives colour and hiding power, such as titanium dioxide for white and iron oxides for reds and yellows.
• Binder (vehicle): The film-forming material, such as acrylic resin, alkyd resin or linseed oil, that holds the pigment and sticks to the surface.
• Solvent or thinner: Water or organic solvents that make the paint fluid enough to apply and then evaporate as it dries.
• Extenders: Inexpensive fillers such as chalk or clay that add body and reduce cost.
• Additives: Small amounts of driers, fungicides, thickeners and anti-settling agents that improve performance.

Properties of a good paint

• Good adhesion: Sticks firmly to the surface without peeling.
• Good opacity: Hides the surface below in as few coats as possible.
• Easy application: Spreads smoothly by brush, roller or spray without runs.
• Reasonable drying time: Dries fast enough for work to continue but slowly enough to level out brush marks.
• Durability: Resists fading, cracking, chalking and wear over time.
• Washability: Can be cleaned without damage.
• Safety: Low in toxic substances and harmful fumes.

The paint system

Paint is usually applied as a system of compatible coats, each with a job to do.

• Primer: The first coat, which seals the surface and helps later coats stick.
• Undercoat: Builds film thickness and provides an even base colour.
• Finishing coat: The final visible coat that gives the colour, sheen and protection.
• Sealers: Special first coats for porous or stained surfaces.
• Compatibility: All coats in a system must be compatible, for example water-based over water-based.

Sheen levels

Paints are produced in different sheen levels, which affect appearance, durability and how well they hide defects.

Worked example: spreading rate

Spreading rate = area covered ÷ volume of paint used

A painter uses 4 litres of paint to cover 48 m² of wall in one coat.

Spreading rate = 48 ÷ 4

Spreading rate = 12 m² per litre

Health and environmental considerations

• Volatile organic compounds (VOCs): Solvents released while paint dries cause headaches, breathing problems and indoor air pollution; low-VOC or VOC-free paints are preferred in hospitals, schools and homes.
• Lead and heavy metals: Old paints may contain lead, which is poisonous, especially to children. Lead paint must not be used, and old coatings suspected of containing lead should be removed with wet methods and dust control, never by dry sanding or burning.
• Allergens and odour: Some paints trigger allergies or strong odours; low-odour, hypoallergenic products suit occupied buildings and sensitive users.
• Standards and labels: Check that products meet Kenya Bureau of Standards (KEBS) requirements and carry recognised eco-labels where specified.
• Disposal: Leftover paint, thinners and washing water must not be poured into drains or soil; dispose of them as the county environment office and NEMA rules require.

Chapter Summary

This chapter provides a comprehensive overview of interior painting, beginning with an introduction to paints that explains their composition and function. Various types of paints are explored, highlighting their specific uses and characteristics. The chapter also examines paint effects, detailing how different finishes can influence the appearance and ambiance of interior spaces. Essential painting tools and equipment are described to ensure proper selection and use for quality results. Colour schemes are discussed in relation to design principles and psychological impact, guiding effective colour choices. Painting techniques and the step-by-step paint application process are presented to achieve professional finishes. The chapter further addresses emerging trends in paint technology, including eco-friendly options that promote sustainability. Finally, it covers repair and maintenance practices necessary to preserve painted surfaces and extend their lifespan.