Surface protection of another kind with the Castillo de San Marcos
Usually, when pontificating on the topic of natural stone, we talk about the need for people to apply surface protection. It’s not often that it’s the reverse – the stone surface providing protection for people. Yet when one considers the Castillo de San Marcos in St. Augustine, Florida, that’s exactly what you see.
In a list of American history’s most impregnable structures, the Castillo de San Marcos must surely rank somewhere near the top. Built by the Spanish sometime between 1672 and 1695, in its more than 300 years of existence, the fort has never once been conquered – and lord knows people have tried, including English General James Oglethorpe in 1740.
What is the secret behind its success?
Florida’s unique coquina stone
When the Spanish decided to build a fort in St Augustine, there was little choice in terms of building materials. The only option seemed to be coquina, a light, porous stone made from a mixture of limestone, various types of sea shells, coral and other materials, which could be found on the east coast of Florida.
Ironically, what seemed to be coquina’s greatest weakness – its many holes and ridges – was what made it so effective. While tougher stones like granite or brick would shatter into pieces at the strike of a cannonball, coquina’s millions air pockets allowed it to compress, and so withstand the assault of cannonballs.
Nothing lasts forever
Nonetheless, while the stone was good at rebuffing bullets and cannon fire, over time it succumbed to the effects of erosion. Today, there is a comprehensive preservation project aimed at keeping the fort’s walls standing strong for years to come.
If nothing else, it’s a good reminder of the importance of sealing any limestone you might have around the home. Household limestone – which doesn’t tend to come mixed with sea shells and compressed over thousands of years – is less porous than coquina, yet still tends to absorb water rapidly. Preventing water damage means you’ll have to implement top-notch limestone protection.
In other words, be sure to keep the enemy – water – at the gates, and seal your limestone with Dry-Treat’s STAIN-PROOF Original™.