# Painting I: What the Medium Decides

Art History I · Artistic Languages · https://tryals.app/learn/art-history-i/painting-i-what-the-medium-decides

## Pigment, Binder, Support

Paint consists of a **pigment** held in a **binder** that sticks it to a **support**. The pigments are largely shared. The Binder decides almost everything about how the picture is made.

| Medium | Binder | Drying | What it permits | What it forbids |
|---|---|---|---|---|
| **Fresco** | Lime plaster | Hours | Permanent wall painting | Revision after setting |
| **Tempera** | Egg yolk | Minutes | Precise line, clear colour | Soft blending |
| **Oil** | Drying oil | Days to weeks | Blending, glazing, revision | Speed |
| **Watercolour** | Gum arabic | Minutes | Transparency, luminous whites | Covering a mistake |
| **Acrylic** | Polymer emulsion | Minutes | Fast layering, any support | Slow blending |

### Fresco imposes a schedule

In **buon fresco**, pigment binds chemically to wet lime plaster. The paint becomes part of the wall itself. 

The painter must finish before the plaster sets. Work is therefore divided into **giornate**, or day-pieces. Corrections require cutting out the dry plaster entirely.

### Oil changes what a picture can be

**Oil** paint was not invented by Jan van Eyck. However, fifteenth-century Netherlandish painters perfected its use.

Its slow drying time permits new techniques:

- **Blending**: smooth transitions worked wet into wet.
- **Glazing**: luminous depth through transparent layers.
- **Revision**: changing composition over weeks of work.
- **Deep, saturated darks**: carrying dense loads of pigment.

### Support matters too

A Panel is rigid, stable, and heavy. Canvas is light, flexible, and portable. 

> **Common pitfall:** treating the medium as a technical detail. The medium dictates what a style can achieve. A tempera panel cannot produce the soft transitions of a Venetian oil painting.

## Practice questions

9 of this lesson's 14 practice questions, with answers. The full set is in the app.

### 1. Sort each capability by the medium that permits it.

**Answer:**

- Fresco: Binds chemically to wall, Planned in day-pieces
- Tempera: Precise line, jewel colour, Fast dry, hatched shading
- Oil: Smooth wet-in-wet blend, Glazes on underpainting

**Why:** Drying time explains almost every entry. Fresco gives hours and imposes a schedule; tempera gives minutes and forces hatching to do the work of blending; oil gives days and permits both blending and glazing. The technique follows from the chemistry.

Page: https://tryals.app/practice/art-history-i/painting-i-what-the-medium-decides/sort-each-capability-by-the-medium-that-permits-it

### 2. Why did the arrival of oil paint change the way a picture could be composed, not just how it looked?

A. Transparent glazes meant complex spatial depth could be calculated beforehand purely through linear drawing
B. A medium revisable over weeks lets a painting be developed rather than executed from a settled design
C. Its rapid drying time allowed painters to establish the entire tonal structure in a single sitting
D. The chemical bond formed with the wet plaster ground removed the necessity of full preparatory cartoons

**Answer:** B. A medium revisable over weeks lets a painting be developed rather than executed from a settled design

**Why:** Because it moved the design decisions **into** the painting. Tempera dries in minutes and requires a settled cartoon transferred to the panel; oil can be reworked for weeks, so the composition can be discovered on the support. That is a change in the practice of making pictures, not merely in their surface.

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### 3. Jan van Eyck invented oil painting.

**Answer:** False

**Why:** **False.** The attribution is Vasari's and is wrong: oil binders were in use before the fifteenth century. What van Eyck and his contemporaries did was develop the technique to a point that made oil the dominant European medium for five hundred years, a real achievement that the invention story obscures.

Page: https://tryals.app/practice/art-history-i/painting-i-what-the-medium-decides/jan-van-eyck-invented-oil-painting

### 4. Which follow from the chemistry of buon fresco?

A. The painter can only cover what can be finished before the plaster sets
B. Correction requires cutting out and replastering
C. The paint layer sits on the surface and can be peeled
D. The work is planned in giornate whose joins remain visible

**Answer:** A. The painter can only cover what can be finished before the plaster sets; B. Correction requires cutting out and replastering; D. The work is planned in giornate whose joins remain visible

**Why:** The fourth describes a secco painting, applied to dry plaster, which does sit as a layer and is far less durable. That difference is why secco passages are so often the parts of a fresco that have been lost, the buon fresco is the wall, and the secco is on it.

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### 5. Complete the account of the media.

**Answer:** A paint is pigment held in a **binder** and applied to a support. In buon fresco the pigment binds as the **plaster** carbonates. A day-piece of fresco is a **giornata**. Transparent layers of oil laid over an opaque underpainting are **glazes**.

**Why:** The first blank carries the lesson: pigments are largely shared across media, so it is the binder that decides drying time, working method and what the picture can be. Change the binder and you change the painting before a subject has been chosen.

Page: https://tryals.app/practice/art-history-i/painting-i-what-the-medium-decides/complete-the-account-of-the-media

### 6. Roughly how many days can an oil painting remain workable, allowing wet-into-wet blending?

**Answer:** 2 (within ±1)

**Why:** On the order of **two days**, varying widely with thickness, pigment and medium added. The precise figure matters less than the comparison: tempera gives minutes and fresco gives hours, so oil's working window is larger by one to two orders of magnitude.

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### 7. Arrange the stages of painting a buon fresco in order.

**Answer:**

1. Plan the composition and divide it into day-pieces
2. Apply the rough plaster layer to the wall
3. Lay the fine intonaco over one day-piece only
4. Paint into the wet plaster within hours
5. Move to the next day-piece the following day

**Why:** The order is imposed by the chemistry, not chosen. Plaster only as much as can be painted before it sets, which means the composition must be divided into day-pieces before work begins, so a fresco is planned to a degree an oil painting never has to be.

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### 8. Egg tempera and oil paint rely on identical pigments, yet produce entirely distinct visual styles. What accounts for this formal divergence, and what does it demand of the painter's method?

A. Tempera prohibits multi-layered glazing because the binder remains wet
B. The choice of rigid panel versus flexible canvas dictates the brushwork
C. Egg yolk alters the chromatic strength of the raw powdered pigments
D. The binder determines the drying rate and the feasibility of blending

**Answer:** D. The binder determines the drying rate and the feasibility of blending

**Why:** Pigments provide hue, but the binder governs behaviour. Egg yolk dries in minutes, enforcing sharp delineation, whereas oil dries over weeks, allowing wet-in-wet tonal transitions. Support affects scale and transport, not the intrinsic handling of the paint film itself.

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### 9. The pigments used in fresco, tempera and oil are largely the same; it is the binder that differs.

**Answer:** True

**Why:** **True**, and it is why the differences between the media are so instructive. The same coloured solid behaves completely differently in lime plaster, egg yolk and drying oil, so the visible differences between a fresco, a tempera panel and an oil painting are differences of chemistry rather than of palette.

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