Barns tend to be red because of the high availability and low cost of red paint. Paint is created by combining a colored pigment, whose hue depends on the mineral that is in it, and a binder such as acrylic or oil to help the color stick. Red paint is made from red ochre, a combination of iron and oxygen. Iron is one of the most plentiful minerals, as the Earth's crust is about 6% iron. Blue and green pigments are mainly made using copper, which is much less plentiful than iron at less than 0.01% of the Earth’s crust, making those paint colors more expensive.
More about barns:
- Barns in Europe were traditionally colored with a mixture of linseed oil and either milk or lime.
- One theory about the origins of red barns is that farmers would add rust to linseed oil in order to avoid mold.
- Whitewash, a combination of lime and chalk, gained popularity for use on barns during the mid-20th century and began to be used as an alternative to red paint because of its cheaper price, non-toxicity and antibacterial properties.