An Olive Oil Acid Coating to Shield York Minster’s Stone
Chemists at Cardiff University have made a water-repelling coating for old limestone from oleic acid, the main fatty acid in olive oil, and it protected samples of York Minster’s stone from pollution damage in the lab. The work has been circulating since December and reached the olive oil trade press this week. Here is what the researchers did, what the olive part really is, and what it does not mean.
What the researchers did
The study, published in the journal Scientific Reports, is by Rachel Walker, Karen Wilson and Adam Lee of Cardiff University, working with Vicki Grassian and colleagues at the University of Iowa. They mixed oleic acid with a fluorinated silane, a highly water-repellent compound, and applied it to limestone, including stone from York Minster, the great Gothic cathedral in northern England. They then exposed the samples to sulfur dioxide and sulfate particles, the pollutants behind acid rain damage.
The coated stone formed much less gypsum, the crumbly mineral that eats away carved limestone. Grassian said in the University of Iowa’s release that the paper shows limestone buildings and statues “can be protected from degradation by atmospheric corrosion.” Olive Oil Times covered the work on January 15.
| Item | Detail |
|---|---|
| Coating | Oleic acid plus a fluorinated silane |
| Test stone | Limestone, including samples from York Minster |
| Threat tested | Sulfur dioxide and sulfate, the chemistry of acid rain |
| Result | Much less gypsum; stone still able to breathe |
| Stage | Laboratory tests, research ongoing |
Why oleic acid
Oleic acid is the monounsaturated fat that makes up most of olive oil, the same molecule we explained in The fatty-acid profile: why oleic acid is the hero. Its shape is what makes it useful here. Karen Wilson told NPR that one end of the molecule “will selectively react with the stone,” while the other, a long hydrocarbon chain, repels water.
That matters because York Minster’s problem is not just today’s rain. Wilson explained that salts left in the stone from industrial-era pollution build up inside it, “eventually crack it, and large features will start to fall off the building.” Earlier coatings sealed the pores, which trapped moisture and encouraged salt and mold. The new layer repels liquid water but still lets the stone breathe. An earlier experiment with linseed oil at York Minster darkened the stone, NPR reported, which is one reason the team wanted something that leaves the color alone.
What it does not mean
- Nobody is going to paint a cathedral with extra virgin. The coating is a lab-made mixture, and oleic acid is only one of its two ingredients.
- These are laboratory results on stone samples. The researchers describe early, promising work, not a treatment in use.
- It is a nice reminder that olive oil chemistry has uses well beyond the kitchen, as it always has (Olive Oil has many uses).
Oleic acid takes its name from olive oil, but the oleic acid sold to industry is often made from other fats and oils. So when a headline says olive oil will save a building, or a cosmetic says it is rich in oleic acid, it may have nothing to do with an olive grove. If the olive matters to you, look for olive oil itself on the ingredient list, not a chemical named after it.
Sources
- Scientific Reports: Preservation of York Minster historic limestone by hydrophobic surface coatings
- ScienceDaily (University of Iowa release): New way to protect historic limestone buildings
- NPR via WUNC: A Dash Of Olive Oil May Preserve British Cathedral
- Olive Oil Times: Olive Oil May be Key to Protection of Ancient Buildings