Graphic-Plastic Materials, Tools and Supports
This domain tests whether you can name, choose and justify the physical chain behind any graphic-plastic work: pigment, binder, vehicle and support. PAU questions here are practical (which paper for a wet wash, why prime a board before oil), so link every material to a behaviour: absorbency, tooth, drying time, permanence.
The four-part chain
- Pigment gives colour; binder forms the film (gum arabic, linseed oil, acrylic polymer, wax, egg); the vehicle/diluent adjusts consistency (water, white spirit, alcohol); the support receives the film.
- The same pigment behaves differently by binder: raw umber in gum arabic stays rewettable (watercolour), in linseed oil it forms a slow-drying paint film.
- Paper: gramaje (g/m²), grain (rough, cold-pressed/medium, hot-pressed/satinado), and encolado (sizing) which controls absorbency. Acid-free and lignin-free for permanence.
- Canvas: linen (strong, low elasticity), cotton (cheaper, more elastic), synthetic; always sized and primed. Oil on unprimed canvas or paper rots the fibres.
- Rigid supports: primed board, sealed MDF or plywood; seal both faces to avoid warping. Cardboard is for studies only.
Tools
- Brushes differ by filament and shape: cerda (stiff, for oil/acrylic), marta or natural hair (soft, watercolour washes), synthetic filament (springy, durable). Shapes: redondo, plano, lengua de gato, abanico, pincel de arrastre.
- Palette knives mix paint; gubias and buriles belong to printmaking, not painting.
- ISO A formats keep the 1:√2 ratio; A0 measures 1 m².
Worked example
Task: choose and justify supports for (a) a watercolour wash and (b) an oil sketch. For (a) use cotton or acid-free cellulose paper of about 300 g/m², cold-pressed so granulating pigments settle; soak and tape it to a board so it dries taut, because thinner paper cockles and pools. For (b) reject paper entirely: use cotton canvas or sealed MDF with two coats of primer plus a lean ground, since oil both penetrates and embrittles unprotected fibre.
Marks-losing traps
- Treating gramaje as a quality guarantee: 300 g/m² wood-pulp paper still yellows.
- Calling acrylic gesso an oil ground; a true oil ground is pigment in drying oil.
- Assuming all watercolour paper is cotton; much of it is cellulose.
- Forgetting that hot-pressed paper kills dry-brush texture and rough paper breaks fine line.