Traditional Barn Red Primer and Paint

I began looking for a good recipe and guide on making traditional barn red paint, I couldn't find one with volumes and weights so I figured I would catalog my attempt.

Traditional barn red paint is made with Iron oxide(III) more commonly known as rust for pigment. Rust is antifungal and antibacterial, making it a good choice to preserve wood. The carrier of the pigment is typically linseed oil or another drying oil that will cure and keep water out. A thinner or thickener is added depending what type of coat you are making.

These materials will also be preferable to weather proof my rabbit hutch as they are non-toxic in low doses if the bunnies chew it.

SAFETY NOTICE: Someone mentioned in the comments about the flammability of drying oils and I feel it should be pointed out more. You can see a few rags with linseed oil on them drying out on some hardware cloth in this instructable. This is a necessary step before you throw out oil soaked rags, as they drying process is exothermic and generates heat. With enough rags or towels in a trash can heating up you can start a fire, usually MUCH later when you are not present.

Please take care to let rags COMPLETELY dry out before throwing them away.

For the primer coat I used the following tools:

2-1/2 Quart paint mixing cup

wooden stir stick

weight scale with cup

gloves

cheap brush pack

I used the following ingredients to blend the paint:

1 Quart low odor mineral spirits (Traditionally turpentine would be used)

1 Quart Boiled linseed oil (cures faster than pure linseed oil)

2 oz Iron Oxide (III) powder

This is quite simple to start, pour one quart of Boiled Linseed oil (BLO) into the mixing cup, followed by one quart of mineral spirits. These two will have density separation initially and form layers, a brief but thorough stir with the wooden stir stick will blend them well. The mineral spirits here is to help thin the paint so it soaks in quickly and gets deeper into the wood before it cures.

I weighed out one ounce of iron oxide and slowly tapped it into the mixing cup while stirring with the other hand. I felt the color was lacking, even though this was a primer coat so I added a second ounce the same way.

So a few notes as I began brushing this primer on! It is VERY thin and soaks into the wood quickly, which is exactly what we are looking for. It is thin enough I considered getting a sprayer to apply it as it ran everywhere off the brush. I did not have a disposable one handy, so maybe next time.

This is a roughly made rabbit hutch made from rough sawn red oak. I planed it where necessary to get good joint fitup, but left it alone other than that. While the BLO soaked into the wood VERY well all over, the rough surface of the saw cut held the iron oxide coloration more evenly and took a darker color. I believe rough sanding all planed surfaces would have helped.

While most of the iron oxide powder stayed suspended I did have to stir somewhat frequently to keep buildup on the bottom of the mixing cup to a minimum, as you can see by the stir stick still in while I was painting.

If it helps you estimate how much you need, I only used about 1-1/2 quarts of the two quarts I mixed up for this 30x30x120 rabbit hutch. Hopefully I will get the heavy color coat on in the next few days and make another instruct able!

I decided to add onto this instructable for the top coat instead of making a new one for the color coat.

The top coat is made with only 3 ingredients:

1 Quart Boiled linseed oil

12 ounces Diatomaceous earth

2 ounces Red Iron oxide (III) Powder

As with the primer, ingredients have been listed many places online and with many variations. The function of the linseed oil to carry the pigment, spread it evenly across the surface, and cure to a weather resistant coating. The diatomaceous earth is simply a thickening agent. This makes the paint easier to apply heavy coats as it runs less. There were MANY different thickeners used from my research, from powdered clay to change pigment as well to certain versions of limestone powder. And finally the iron oxide pigment gives us the "red" color.

I mixed this the same as the primer. I started with the liquid in the mixing tub, 1 quart boiled linseed oil. I then added the diatomaceous earth(DE) 1 oz at a time and stirred it in. I noticed it wasn't thickening very much so I skipped to adding 2 oz at a time. I stopped at 12 oz of DE in 1 quart of BLO. I think I could have easily added more but it looked good enough for my needs. I will say the DE tended to clump in mixing and I wish I had done this in a larger bucket so I could have mixed it more aggressivly without risk of spilling.

I added in the iron oxide after that, 1 oz at a time until the color looked right. I stopped at 2 oz. This left me with roughly 1-1/2 quarts of topcoat paint.

Not much to say about application, it painted on well and the pigment stayed suspended much better. You can see here half is primed half is painted. The primer dried lighter than it was when I applied it, however the opposite was true about this topcoat. It definitely dried darker.

Here is the rabbit hutch with 1 topcoat of paint cured on it. It was wet for about 1 day, then tacky for a total of 4 days. This paint takes a long time to dry, but it is soaking into the wood and curing the wood surface into a weather resistant coating. I have seen this about 1/16" deep in my broken shovel handles :D.

Conclusion notes:

This paint is darker than I expected for a "Traditional Barn Red" you see in stores. I'm not sure if the vibrant paint in stores is a traditional color, as many metal oxides were used in different formulations of this over the years (look up "Falu Red") I believe lead oxide and mercury oxide have much brighter red pigments, and my research shows me that just about any metal oxide would have the anti-fungal/anti-bacterial properties I wanted. Iron oxide is however very safe to handle and or ingest for bunnies nibbling on a rabbit hutch. All and all I am very happy with the hutch, the outside may get 1 more coat before I make a roof (which will have a traditional whitewash color)