system
Given the following post, respond as if you're commenting on Reddit:
human
Why are barns painted red?

At least with the American ones, just about every barn I've seen is painted that same dark red. Is it culture, superstition, availability, all of the above?
gpt
Centuries ago, European farmers would seal the wood on their barns with an oil, often linseed oil - a tawny-colored oil derived from the seed of the flax plant. They would paint their barns with a linseed-oil mixture, often consisting of additions such as milk and lime. 

The combination produced a long-lasting paint that dried and hardened quickly. 

(Today, linseed oil is sold in most home-improvement stores as a wood sealant). 

As for the red, there are two predominant theories:

* Wealthy farmers added blood from a recent slaughter to the oil mixture. As the paint dried, it turned from a bright red to a darker, burnt red.

* Farmers added ferrous oxide, otherwise known as rust, to the oil mixture. Rust was plentiful on farms and is a poison to many fungi, including mold and moss, which were known to grown on barns. These fungi would trap moisture in the wood, increasing decay.


Regardless of how the farmer tinted his paint, having a red barn became a fashionable thing. They were a sharp contrast to the traditional white farmhouse.

As European settlers crossed over to America, they brought with them the tradition of red barns. In the mid to late 1800s, as paints began to be produced with chemical pigments, **red paint was the most inexpensive to buy**. 

Red was the color of favor **until whitewash became cheaper**, at which point white barns began to spring up.

Today, the color of barns can vary, often depending on how the barns are used.