Painting: media and techniques

In short

Painting is the laying of a coloured film on a support, and every technique is governed by one chain: pigment + binder (vehicle) + diluent, on a ground, on a support. Choice of binder decides working time, transparency, how thick a layer may be, whether the dry film is reversible, and how long the work survives — so "media and techniques" is really applied material science for the studio. It is examined in BFA/BVA studio practice vivas and theory papers (material and method, Indian traditional techniques, conservation basics) and in UGC-NET Visual Arts. It is used daily by studio painters, muralists, scenic and background painters, illustrators, conservation assistants at labs such as NRLC Lucknow and INTACH, art teachers, and product/demo roles at colour makers like Kokuyo Camlin, Pidilite (Fevicryl) and Brustro.

Explained

Pigment, binder, diluent, ground, support

• Pigment: insoluble coloured particles. Named internationally by Colour Index: PW6 titanium white, PW4 zinc white, PY43 yellow ochre, PR101 red oxide, PR108 cadmium red, PB29 ultramarine, PB15:3 phthalocyanine blue, PG7 phthalo green, PV19 quinacridone, PBr7 umber/sienna, PBk7 carbon black. Read the CI number, not the fancy marketing name — "Crimson" may be PR83 (fugitive) or PV19 (permanent).
• Dye vs pigment: a dye dissolves and stains; a pigment stays as particles suspended in the binder. Student-grade "hues" often use dye-based or extended pigments and fade.
• Binder: the film former — drying oil, acrylic emulsion, gum arabic, egg yolk, lime, wax, casein, animal glue.
• Diluent/solvent: thins the paint and evaporates — water, turpentine, odourless mineral spirit (OMS). A medium modifies the binder (stand oil, damar varnish, alkyd, acrylic gel, retarder).
• Extender/filler: chalk, barytes, marble dust — cheapen and body the paint, reduce tinting strength.
• Support: stretched fabric (cotton duck, linen), rigid panel (MDF, plywood, hardboard), paper, wall plaster, metal.
• Ground: the prepared white or toned layer between support and paint — controls absorbency, tooth and brightness.
• Sizing: seals the support from the binder. Traditional animal glue (rabbit-skin) is hygroscopic and brittle; modern practice uses PVA size or an acrylic dispersion.
• True gesso = chalk/gypsum + animal glue; brittle, so only on a rigid panel; absorbent and ideal for tempera and gilding. Acrylic "gesso" = titanium white + chalk in acrylic binder; flexible, safe on canvas, but not real gesso.
• Half-chalk and oil grounds are less absorbent and give slicker handling for oils.

Oil painting

• Binder: drying oils that cure by oxidative polymerisation (they absorb oxygen and cross-link; they do not "dry" by evaporation), so an oil film gains weight as it sets.
• Linseed (highest iodine value, fastest drying, yellows most), walnut (intermediate), poppy and safflower (slower, least yellowing — used for whites and pale blues). Stand oil (heat-bodied) levels brushmarks; sun-thickened oil dries faster.
• Fat over lean (the central rule): each successive layer must contain more oil than the one below. A lean, fast-drying layer over a fat, slow one dries faster, shrinks more and becomes brittle, so the top film cracks.
• Thick over thin, slow over fast: large impasto goes on last.
• Drying order of pigments matters: umbers, siennas, Prussian blue and lead white dry fast; ivory black, vermilion, cadmiums and alizarin dry slowly.
• Techniques: *alla prima* (wet-in-wet, finished in one session); glazing (transparent dark over light, builds depth); scumbling (opaque/semi-opaque light dragged over dark); impasto (ridged paint, knife or stiff brush); grisaille/underpainting (monochrome value study, then colour glazes); dry brush; sgraffito (scratching through); frottage/tonking; oiling out to restore sunken passages.
• Defects: *sinking in* (matte dull patches — binder absorbed by ground), cracking (fat-over-lean violation or excess solvent), wrinkling (too much oil), blooming (bluish haze from damp varnish), yellowing, blanching.
• Alkyd paints and mediums speed drying; water-mixable oils avoid solvents.
• Touch-dry in 2-10 days; varnish only after about 6-12 months of curing.

Acrylic, watercolour, gouache, tempera and other media

• Acrylic: waterborne polymer dispersion; dries by water evaporation and coalescence of the particles. Fast, water-cleanable, flexible, dries slightly darker and glossier, water-insoluble once dry, so no reworking by wetting. Needs retarder/flow improver in dry climates; mediums include gloss/matte, gel, modelling paste. Apply an isolation coat (dilute gloss medium) before varnishing, because the paint film itself is soluble in the varnish solvent. Low glass-transition temperature means the film stays slightly soft and picks up dirt.
• Watercolour: pigment in gum arabic with glycerine (humectant), ox gall (wetting agent) and sometimes honey. Transparency comes from light passing through to the white paper. Terms: flat wash, graded wash, wet-on-wet, wet-on-dry, lifting, reserving whites, masking fluid, granulating vs staining pigments, charging. Work light to dark; no white paint.
• Gouache: opaque watercolour with chalk added; matte, dries lighter in value, reworkable, used for illustration and design boards.
• Egg tempera: yolk emulsion binder, on rigid gessoed panel; dries in seconds, so modelling is done by hatching and cross-hatching in thin layers; cannot be used thickly; dries paler and darkens on varnishing. Film is tough and does not yellow.
• Casein (milk protein) — matte, hard, used for murals and models. Encaustic — beeswax with damar resin, fused with heat. Pastel and oil pastel — minimal binder, needs fixative and glazing.
• Fresco buono (true fresco): pigment in lime water painted into wet lime plaster (intonaco over arriccio); sets by carbonation, the pigment locked in a crystalline calcite skin. Alkali-stable earth and mineral pigments only; work planned in giornate (a day's patch); design transferred by cartoon, pouncing (spolvero) or incising. Fresco secco is painted on dry plaster with a binder and is less durable.
• Indian traditional techniques (frequently asked): Ajanta is tempera on mud plaster (secco), not true fresco; Kerala murals use the *panchavarna* five-colour scheme of mineral and vegetable pigments in a vegetable binder; Tanjore painting builds raised chalk-and-adhesive gesso relief set with gold foil and stones; Rajasthani/Pahari miniature uses wasli (layered handmade paper), burnished with agate, squirrel-hair brushes, pigments such as *hingul* (vermilion), *harital* (orpiment), *safeda* (lead white), ultramarine and shell gold; araish/Jaipur fresco is burnished lime and marble-dust plaster; Kalamkari uses myrobalan-treated cotton with a bamboo *kalam* and iron/alum mordants; Madhubani, Warli, Phad, Pichwai each have a fixed pigment and ground tradition.

Supports, brushes and the preparation sequence

• Canvas: cotton duck (cheap, weaker) or linen (stronger, finer weave, costlier). Fabric weight is quoted in oz/sq yd or GSM; 10-12 oz is normal for stretching.
• Stretcher: mitred bars with a bevelled inner edge and keys/wedges at the corners to re-tension; cross-bar needed beyond about 100 cm. Staple or tack from the centre of each side outwards.
• Paper: cotton rag (archival, pH-neutral) vs wood-pulp; hot press (smooth), cold press/NOT (medium), rough; 300 GSM or heavier resists cockling, lighter sheets are stretched when wet.
• Brushes: hog bristle (stiff, for oil/acrylic), sable and kolinsky (soft, watercolour), synthetic taklon; shapes — round, flat, bright, filbert, fan, rigger, mop; plus palette knife and painting knife.
• Standard preparation sequence: stretch → size → 2-4 thin gesso coats, each sanded and crossed at 90° to the last → optional toned imprimatura → drawing/transfer → underpainting → colour layers → oiling out if needed → varnish.
• Varnish: must be removable — natural damar (yellows) or synthetic (MSA, Regalrez, acrylic resin); gloss, satin or matte; many carry UV absorbers. Works on paper are protected by acid-free mount board and glazing instead.

Colour behaviour, permanence and standards

• Subtractive mixing for paint (pigment primaries approximated by cyan-ish, magenta-ish and yellow-ish paints); additive mixing applies to light, not paint.
• Hue, value, chroma/saturation; tint (+ white), shade (+ black), tone (+ grey). Low-chroma greys made by mixing complements are livelier than black-mixed greys.
• Opacity/transparency depends on the refractive-index difference between pigment and binder — this is why a pigment can be transparent in oil and opaque in acrylic or gouache.
• Tinting strength (how far a pigment takes white) and oil absorption (g of oil per 100 g pigment) govern handling and drying.
• Lightfastness: ASTM D4303 ratings I (excellent) to V (very poor) — use I and II for professional work; the Blue Wool scale runs 1-8 with 8 most permanent. Fugitive pigments to avoid in exhibition work include alizarin crimson lake types and many fluorescents.
• Labelling of artists' colours in India must satisfy the Legal Metrology (Packaged Commodities) Rules, 2011 declarations; children's paints are covered by the toy-safety standard and the BIS toy quality control order. Many imported tubes carry the US ASTM D4236 health-labelling statement — useful but not an Indian requirement.
• Hazardous pigments: lead white (basic lead carbonate), cadmiums, cobalt, chrome, vermilion (mercury), orpiment (arsenic), and old emerald green. Risk is from dust and ingestion, not from touching a wet film: no sanding dry paint without a mask, no eating or pointing brushes with the lips, wet-wipe surfaces instead of sweeping.
• Solvents: turpentine and OMS need ventilation; store in closed metal containers, never pour down a drain. Solvent and rag waste is hazardous waste under the Hazardous and Other Wastes (Management and Transboundary Movement) Rules, 2016; general studio waste falls under the Solid Waste Management Rules, 2026. Oily rags can self-heat — keep them flat or in water. Workplace safety in a commercial studio or paint factory is governed by the OSH&WC Code, 2020, in force from 21 November 2025 in place of the former Factories Act.
• Rights and trade: the painter's copyright and moral rights (right of attribution and against distortion) arise under the Copyright Act, 1957; a work more than 100 years old is an antiquity under the Antiquities and Art Treasures Act, 1972 and cannot be exported freely. Under GST (slabs of 5%, 18% and 40% since 22 September 2025), artists' colours and brushes are bought at the standard rate while original paintings and sculptures fall in the lower slab — rates on art have been revised more than once, so confirm the current notification for HSN 9701 before invoicing.

Key points

• Paint - pigment (colour) + binder (film former) + diluent (thinner); change the binder and you change the whole technique.
• Fat over lean - every upper oil layer must contain more oil than the one below, or it cracks.
• Thick over thin, slow over fast - impasto and slow-drying colours belong in the final layers.
• Oil cures by oxidation, acrylic dries by water loss and coalescence, watercolour and tempera dry by evaporation of water from their binders.
• True gesso is brittle - rigid panel only; acrylic gesso is the flexible substitute for canvas.
• Size first - unsized fabric lets oil reach and rot the fibres.
• Glazing is transparent dark over light; scumbling is opaque light over dark.
• Egg tempera needs hatched thin strokes on a rigid panel; it never cracks but cannot be thick.
• Gouache dries lighter, acrylic dries darker and glossier, tempera dries paler - allow for the shift while mixing.
• Buon fresco is painted into wet lime and fixed by carbonation; secco is painted on dry plaster with a binder.
• Ajanta is secco tempera on mud plaster, not true fresco - a standard exam trap.
• Colour Index names (PB29, PW6) identify a pigment; trade names do not.
• ASTM lightfastness I-II / Blue Wool 7-8 for any work meant to last.
• Varnish must be removable and oils must cure 6-12 months first; acrylics need an isolation coat beneath the varnish.
• Pigment hazards are dust-and-ingestion hazards - ventilate, wet-clean, never dry-sand cadmium or lead films.
• Supports: canvas flexes (oil/acrylic), panel is rigid (tempera, gilding, gesso relief), 300 GSM cotton rag paper for watercolour.
• Indian traditions each pair a specific ground with a specific binder - wasli with gum, Tanjore gesso with gold foil, panchavarna with vegetable binder.

Formulas and examples

Example 1 — preparing a 90 × 60 cm canvas and its cost.

• Bar depth t = 4 cm, wrap a = 5 cm → cut = (90 + 8 + 10) × (60 + 8 + 10) = 108 × 78 cm.
• From 150 cm wide cotton duck at ₹250 per running metre, 0.78 m is needed → ₹195.
• Painted area = 0.90 × 0.60 = 0.54 m²; 3 gesso coats = 1.62 m² of coverage. At a spreading rate of 8 m²/L, gesso needed = 1.62 ÷ 8 = 0.203 L; at ₹600/L → ₹122.
• Material cost before stretcher bars ≈ ₹317.

Example 2 — fat over lean for three layers, 60 ml of medium each.

• Layer 1 at 1:3 → 15 ml oil + 45 ml OMS, f = 0.25.
• Layer 2 at 1:1 → 30 ml + 30 ml, f = 0.50.
• Layer 3 at 2:1 → 40 ml + 20 ml, f = 0.67.
• f rises 0.25 → 0.50 → 0.67, so the rule is satisfied. Reversing layers 1 and 3 would put a lean film over a fat one and crack the surface within months.

Example 3 — PVC of two oil paints.

• Titanium white: 100 g pigment, density 4.0 g/cm³ → V_p = 25 cm³. Oil absorption 20 g/100 g; linseed density 0.93 g/cm³ → V_b = 20 ÷ 0.93 = 21.5 cm³. PVC = 25 ÷ 46.5 = 53.8%.
• Burnt umber: 100 g, density 3.0 → V_p = 33.3 cm³. Oil absorption 60 g/100 g → V_b = 60 ÷ 0.93 = 64.5 cm³. PVC = 33.3 ÷ 97.8 = 34.1%.
• The umber paint is far oil-richer (lower PVC) — softer, glossier, more prone to yellowing; the titanium paint is stiffer and more opaque.

Example 4 — enlarging a sketch by grid.

• Sketch 30 × 20 cm onto a 120 × 80 cm canvas: AR both = 1.50, so k = 120/30 = 4. A 2 cm grid on the sketch becomes 8 cm on the canvas; 15 × 10 = 150 squares.
• Same sketch onto a 120 × 90 cm canvas: AR = 1.333 ≠ 1.50. Matching the width (k = 4) gives an image 120 × 80 — a 10 cm band left bare. Matching the height (k = 120/... = 90/20 = 4.5) gives 135 × 90 — 15 cm must be cropped from the width. Decide the crop before drawing, not after.

Example 5 — selling the 120 × 90 cm painting.

• Area = 1.20 × 0.90 = 1.08 m² = 1.08 × 10.7639 = 11.63 sq ft. At ₹8,000 per sq ft → ₹93,000, rounded to a list price of ₹95,000.
• With a 40% gallery commission the artist receives 95,000 × 0.60 = ₹57,000.
• If registered under GST and the lower 5% slab applies to the original painting, tax = ₹4,750 and the invoice is ₹99,750; the 18% GST paid on tubes and canvas is input credit against it. Verify the current HSN 9701 rate before raising the bill.

Where it is used

• Studio and gallery practice: solo and group shows through galleries and auction houses — Saffronart, Pundole's, AstaGuru; events such as the Kochi-Muziris Biennale and India Art Fair.
• Public and commercial murals: metro stations and public-wall programmes (Delhi, Bengaluru, Kochi metros; St+art India walls in Mumbai and Delhi), hotel and corporate commissions — exterior work demands lightfast pigments and weather-stable acrylic or mineral systems.
• Film, television and theatre: backdrop and scenic painting at Film City and Ramoji Film City, set texturing and ageing, matte-painting references for VFX.
• Conservation and museums: assistant and technician roles at NRLC Lucknow, INTACH art-conservation centres, National Museum and state museum labs, IGNCA — varnish removal, consolidation, retouching with reversible media.
• Colour industry and retail: product development, quality control and demonstration for Kokuyo Camlin, Pidilite Fevicryl, Brustro, Anupam; workshop and demo artists.
• Teaching, illustration and craft clusters: BFA/B.Ed and NET-qualified art teaching, children's-book and editorial illustration, animation background painting, and traditional clusters such as Srikalahasti kalamkari, Mithila/Madhubani, Thanjavur and Kerala mural ateliers.

Interview questions

• Q: What are the three essential constituents of any paint? A: Pigment for colour, a binder that forms the dry film, and a diluent that thins the paint and then evaporates; extenders and additives are optional.
• Q: State and explain the fat-over-lean rule. A: Each successive oil layer must hold more oil than the layer under it, because an oil-poor film dries faster and shrinks more; put on top of a fatter layer it cracks.
• Q: Why can true gesso not be used on stretched canvas? A: Chalk-and-glue gesso is hard and brittle, so it cracks with the movement of a flexible fabric; it belongs on a rigid panel, and acrylic gesso is used on canvas.
• Q: Difference between glazing and scumbling? A: Glazing is a transparent darker film over a lighter dry layer, deepening colour; scumbling is a broken opaque or semi-opaque lighter film dragged over a darker one.
• Q: Are the Ajanta paintings frescoes? A: No — they are tempera on dry mud plaster with a lime finish, that is a secco technique; buon fresco means painting into wet lime plaster.
• Q: Why does oil paint yellow and which oil yellows least? A: The oxidised linseed film develops yellow chromophores and darkens; poppy and safflower oils yellow least, which is why they are used in whites and pale tints.
• Q: What does "sinking in" mean and how do you treat it? A: Dull matte patches where an absorbent ground has drawn the binder out of the paint; it is corrected by oiling out with a thin film of medium before the next layer.
• Q: Why is an isolation coat applied to an acrylic painting before varnishing? A: Because the dry acrylic paint film dissolves in the same solvents as the varnish, so a clear coat of gloss medium is needed to let the varnish be removed later without lifting the paint.
• Q: How do you judge whether a colour is fit for exhibition work? A: Check the Colour Index pigment number and the lightfastness rating — ASTM I or II, or Blue Wool 7-8 — not the trade name.
• Q: How are cadmium and lead-based colours handled safely? A: Treat them as dust and ingestion hazards: no dry sanding, no spraying, wet-clean the bench, keep food away, wear gloves, and dispose of solvent and rags as hazardous waste.
• Q: Why does gouache dry lighter while acrylic dries darker? A: Gouache contains chalk and dries matte, scattering more light; the milky acrylic binder turns clear and glossy on drying, so the colour appears deeper.
• Q: How long should an oil painting cure before varnishing, and why? A: About 6-12 months depending on thickness, because the oil film continues to oxidise; varnishing too early traps solvent and the film can bloom or wrinkle.

Common mistakes

• Painting a lean, turpentine-heavy layer over a fat one — and then blaming the cracking on the canvas.
• Using true gesso or rabbit-skin glue on stretched canvas, or skipping sizing so the oil reaches the fibres.
• Calling Ajanta "fresco" and confusing buon fresco with fresco secco in theory papers.
• Mixing colours without allowing for the drying shift — gouache and tempera lighten, acrylic darkens.
• Over-thinning acrylic with plain water (above roughly a 1:1 ratio) so the film is under-bound and powders off; use a medium instead.
• Buying by trade name and ignoring the Colour Index number and lightfastness rating, then losing a crimson or a violet within a year.
• Varnishing an oil painting weeks after finishing it, or varnishing acrylics with no isolation coat; and dry-sanding cadmium or lead films without a mask or extraction.

Related topics

Sculpture: modelling, carving and casting · Printmaking: relief, intaglio and screen printing · Photography: camera, light and composition · Colour theory and composition · Indian art history: murals, miniatures and folk traditions · Art conservation and archival framing.