Why Are Clay Courts Red? Red vs Green Clay

The clay court is the most recognisable surface in tennis: a red field, white lines and a player sliding across it. Yet clay is not one colour. In Europe it is brick red; in the eastern United States it is grey-green. This article answers three questions in the red clay vs green clay comparison: where the red comes from, what green clay is, and how the two differ in material, play and appearance. By the end you can look at a photograph of a court and say which clay you are seeing, and decide which tone to choose when bringing that colour to a wall.

Where the colour comes from: called clay, made of brick

Almost all red clay courts today are made not of natural clay but of crushed brick. The red comes from the brick itself: when clay is fired, the iron in it oxidises and gives brick its familiar reddish tone. That is why the colour of a court depends on the brick used; the range runs from light yellow to deep red, and the red of one venue is never quite the red of another.

The names of the surface tell the same story from language to language. French "terre battue" means beaten earth and Italian "terra rossa" means red earth; in German the material is called "Ziegelmehl", literally brick flour. English "clay" describes how the surface looks rather than what it is. Nor is brick the only option: there are courts of burnt shale in Britain and of crushed ant-bed soil in parts of Australia. A general comparison of the surfaces is given in court surfaces and their colours; this article deals with clay alone.

How red clay began

The story of red clay starts at the end of the nineteenth century in Cannes, on the French Riviera. As it is told, the grass court of the English twin brothers who were the champions of the day could not stand up to the Mediterranean sun. The solution was to cover the grass with a fine powder, obtained from broken terracotta pots made in the nearby town of Vallauris. The idea caught on, dozens of courts in Cannes were soon built the same way, and brick dust gradually replaced the pot dust.

Early in the twentieth century, a faster-draining surface made from a mix of crushed brick and burnt shale was developed in England. The logic of today's courts is the same: draining layers below, a fine powder on top.

The layers of a clay court

Red is only the surface of the court. The figures published for the courts on which the French Open is played give the section of a typical clay court; the numbers vary slightly from source to source.

At the top lies 1–2 millimetres of red brick dust. This is the layer that gives the colour and the slide.

Beneath it is about 6–8 centimetres of compacted white limestone. This is the real playing base of the court.

Below that comes roughly 7–10 centimetres of clinker, a coal residue. It holds water and gives the court its flexibility.

At the bottom lies 25–30 centimetres or more of gravel or crushed stone, whose job is to carry the court and drain the water.

This section explains two things. First, the red layer is so thin that where it wears away the pale base beneath shows through; the colour of the court is a covering that is regularly renewed. Second, a clay court is a living surface that needs care: it is watered, swept and compacted with a roller.

What green clay is

Green clay is made of stone, not brick. Its material is metabasalt, a hard greenish rock found in the Blue Ridge Mountains of Virginia in the United States; the rock is crushed, screened and mixed in set proportions. The surface was developed in the early 1930s by an American engineer looking for a more consistent bounce; it was first used in 1932 in the state of Maryland and became known under the trade name Har-Tru. According to its manufacturer, the surface is porous and dries quickly after rain.

Its colour is not a bright green but a grey-green. It is found mainly in the eastern and southern United States and in central and eastern Canada. In Europe and Latin America, the usual clay court is red.

Red clay vs green clay: the differences

Material

Red clay is fired clay, that is brick, ground down; green clay is crushed natural rock. Both are built as a loose, granular top surface over a base that drains water.

Colour

Red clay is a warm brick tone that darkens with moisture. Green clay is a cool, greyish green. On a red court the yellow ball sets up a strong contrast; on a green court the difference in tone is softer.

Play

Both are slow surfaces: the ball loses part of its speed when it lands and bounces relatively high, players slide into their shots and points last longer. Green clay is considered slightly harder and slightly faster than red. On both, the ball leaves a mark, which helps to show whether a ball was in or out.

Geography and tournaments

The professional clay season is played in spring, mostly in Europe and on red clay; the big tournaments in Monte Carlo, Madrid and Rome fall in this period, as does the French Open, the only one of the four Grand Slams played on clay. The best-known home of green clay on the professional calendar is the women's tournament played in Charleston, in the US state of South Carolina. Green clay also has a Grand Slam past: the US Open was played on it for three years, from 1975 to 1977.

Telling the two clays apart in a photograph

In a photograph of a court, three signs are usually enough. The first is colour: a brick or terracotta tone means red clay, a matt greyish green means green clay; the green of a hard court is flatter and more saturated. The second is the surface: clay shows footprints and slide marks, worn pale areas around the baseline and brush marks; a hard court shows none of these. The third is the place: a clay court photographed in Europe or Latin America is almost always red, while one photographed on the east coast of the United States may be green.

Does the colour of clay change the game

What changes the game is the material, not the colour. The best-known test came in Madrid in 2012, when the red clay was dyed blue so that the ball would show up better on television. Players found the surface slippery, and the tournament went back to red the following year. Red holds its place through a tradition of material, not a design decision.

Moisture, on the other hand, changes the colour every day. A watered court darkens and the dust settles; a court that dries out turns paler and dustier. Because the surface absorbs water, play can continue in light rain. At this time of the season the tour is on hard courts; the week's tournaments can be followed in Aurecort's tennis this week piece.

Step by step: bringing clay-court colour to a wall

Step one is to decide which clay you want. Red clay gives a warm, familiar palette; green clay a calm and unusual one.

Step two is to choose the tone. A freshly watered court is a dark, saturated terracotta; a dry court is pale and dusty. The dark tone makes a strong focal point; the pale tone is easier to carry over large areas.

Step three is to set the proportion. Red is a dominant colour; the size of the red area in the work is considered together with the other warm tones in the room.

Step four is to know the opposite colour. Red and green sit opposite each other on the colour wheel; red clay is balanced by green surroundings, green clay by wood and warm white.

Step five is the surface. The dusty, matt texture of clay is more convincing on a matt surface; court-themed works can be seen in the Framed Art Series in the standard 50 × 70 cm format. How colour, texture and composition work together is covered in tennis wall art: colour, texture and composition.

Common mistakes

Taking a clay court for clay is the first misconception. Today's red surface is crushed brick, not natural clay.

Taking green clay for dyed red clay is the second. Green clay is a different material: crushed metabasalt.

Thinking the red layer is thick is the third. The dust that gives the colour is only a millimetre or two; the body of the court is limestone, clinker and gravel.

Assuming that all clay courts are the same red is the fourth. The tone changes with the brick used and with the moisture on the day.

Believing that colour sets the speed is the fifth. Speed is set by material, compaction and moisture; the blue clay experiment showed as much.

Spreading red over every surface of a wall is the sixth. Brick red works as the focal point of a single piece and needs a neutral area around it.

Frequently asked questions

Why are clay courts red?

Because the surface is crushed brick, and brick turns reddish when the iron in the clay oxidises during firing. This dust is only 1–2 millimetres thick; the limestone beneath it is white.

Where is green clay used?

Mainly in the eastern and southern United States and in central and eastern Canada. Its best-known example on the professional calendar is the women's tournament in Charleston.

Is green clay faster than red clay?

Slightly. Green clay is considered a little harder and faster than red; both are still slow compared with hard courts and grass.

Has there ever been a blue clay court?

It was tried for one year at the tournament in Madrid in 2012, when the red clay was dyed blue. Players found the surface slippery and the tournament returned to red in 2013.

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