What the Paint Is Standing On
A painting is a layered stack. Each layer performs a distinct role:
- The support carries the entire structure.
- The size seals the support from oil.
- The ground provides a stable surface for the Paint.
Supports
Panel provides a rigid surface, but it is heavy. Canvas is light and portable.
- Linen: Spun from flax with high tensile strength. It resists humidity changes.
- Cotton duck: Cheaper and weaker. It slackens in damp air and tightens in dry air.
Canvas frames come in two types:
- A stretcher has expandable keyed corners to adjust tension.
- A strainer has fixed corners and cannot be adjusted.
Sizing and Grounds
Drying oils rot raw cellulose fibres. Size seals the fabric to prevent this decay.
- Animal glue size is prepared at 7 per cent by weight in water, or 70 grams per litre.
- A modern PVA size is non-hygroscopic and will not crack canvas with humidity changes.
Grounds
| Ground | Composition | Best used on |
|---|---|---|
| Traditional gesso | Chalk or gypsum in glue | Rigid panel only |
| Oil ground | White pigment in Drying oil | Canvas or panel |
| Acrylic primer | Pigment in acrylic emulsion | Canvas or panel |
Common pitfall: omitting the size layer. Raw canvas will turn brittle and rot under oil paint.