We’ve been experimenting with exterior wood paint with some great results.
The research is based on the traditional Scandinavian red paint, which is a base of linseed oil with various things added. One description:
Centuries ago, European farmers sealed the wood on their barns with an oil, often linseed oil, which was a sort of tawny-colored oil made from flax seeds. They painted their barns with this linseed-oil mixture, often adding milk and lime. The combination produced a long-lasting paint that dried and hardened quickly. Today, linseed oil is still used to seal wood.
Historically, “barn red” is not the bright, fire-engine red that we often see today, but more of a burnt-orange red. As to how the oil mixture became traditionally red, there are two predominant theories:
Sometimes 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.
Some 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. So it made a lot of sense to add rust to the paint, which would also give it a red tinge.
Both blood (often ox blood but not always) and ferrous oxide are used around the world in traditional paint because they both have good properties for long lasting, anti fungal paint.
We decided to go the Ferrous Oxide route since we didn’t have any ox blood in the fridge. But we did have red coloring from MilkPaint.com which is a mix of casein (whey) and natural earthen pigment (sort of ferrous oxide).
We mixed the milk paint coloring with boiled linseed oil and citrus solvent. The citrus solvent was to dilute the oil so that it seeped deeper into the wood.
If you want to get the real deal boiled linseed oil you can get it from SolventFreePaint.com. It is so natural you can practically drink the stuff (don’t). But you pay a pretty penny for it. We just went with the boiled linseed oil from the local hardware store. Yes it is loaded with emulsifiers and other nasty stuff but we just pretend it is natural.
The results are pretty astounding. Below you can see the Brooklyn Show House green roof. We built a bulkhead and pergola (for solar PV and water heating) out of old salvaged wood. We painted it with the boiled linseed oil mix. It works really, really well.
Below is what it looked like before painting it. It looks fine. The natural look is beautiful too. But the beauty of the linseed oil paint is the synthesis of beauty as function. It is not simple decoration. It will extend the wood from maybe 10-15 years to maybe 50-60 years. That is pretty phenomenal.