A World Built of Oyster Shells

Earlier this week, I wrote about the historic use of oyster shells for constructing roads on the North Carolina coast. But coastal people didn’t only use oyster shells for road building. Particularly before the Civil War, they also used oyster shells as an important source of lime.

Burnt down in kilns, an incredible tonnage of oyster shells was used in making cement, mortar, bricks, wall plaster and whitewash.

The ruins of St. Philip's Episcopal Church at the Brunswick Town State Historic Site, Brunswick County, N.C. Photo by Tim Buchanan. Courtesy, Preservation North Carolina

The ruins of St. Philip’s Episcopal Church at the Brunswick Town/Fort Anderson State Historic Site, Brunswick County, N.C. Photo by Tim Buchanan. Courtesy, Preservation North Carolina

The remains of Brunswick Town, for example, founded in 1725 and the first permanent European settlement on the Lower Cape Fear, show that the builders made the foundations of their homes out of a lime cement produced from oyster shells.

First they burnt the shells to make lime, and then they mixed that lime with sand, water, and crushed oyster shells.

Likewise, the walls of Fort Johnston, built in 1802 to protect the mouth of the Cape Fear River, consisted solely of what its slave builders called a “batter” of burnt-down oyster shells and pitch pine.

The Lane House, Edenton, N.C., ca. 1718-19. This is during the early stage of its restoration in 2015. Courtesy, Charlotte Business Journal

The Lane House, Edenton, N.C., ca. 1718-19. This is during the early stage of its restoration in 2015. Courtesy, Charlotte Business Journal

Similarly, the builders of the first Cape Hatteras Lighthouse, which was in service from 1802 to 1871, used a lime mortar that was made out of burnt oyster shells.

Coastal builders also used lime made from burning oyster shells to make plaster, whitewash and paint.

In Edenton, for instance, the Lane House, built circa 1718-19 and the state’s oldest known domicile, has interior walls covered with a whitewash made from slaked lime produced from burnt oyster shells.

Oyster Shells in Fields and Gardens

Lime made from burning oyster shells had another important use on the North Carolina coast as well. Coastal people also produced lime from oyster shells in order to fertilize their fields and gardens.

Then, as now, lime (which is primarily calcium carbonate), was a crucial fertilizer for many crops. It increased the pH of acidic soils; was a source of magnesium and calcium; improved water penetration in acidic soils; and heightened the nutrient uptake of nitrogen, potassium and phosphorous in plants grown in those soils.

Before the Civil War, the major and often only source of lime for fertilizing crops in coastal North Carolina was oyster shells.

Later in the 19th century, farmers often used marl as a source of calcium carbonate for their crops. Marl is made up of a mix of calcium carbonate and clay and is abundant on the state’s southern coast—there are still large marl pits being mined along the coast, in fact.

Edmund Ruffin’s An Essay on Calcareous Manures was a very influential 1852 treatise on the advantages of fertilizing crops with marl. Courtesy, Library of Congress

Edmund Ruffin’s An Essay on Calcareous Manures was a very influential 1852 treatise on the advantages of fertilizing crops with marl. Courtesy, Library of Congress

Though southern agricultural reformers such as Edmund Ruffin had advocated the use of marl as a fertilizer before the Civil War, farmers and planters were slow to adopt its use until later in the century.

Until marl grew more popular and commercial limes (often made out of burnt limestone) became more available, many coastal farmers continued to rely on lime made from burning oyster shells.

Even today many of my neighbors on the North Carolina coast continue to use oyster shells as a source of lime for their grapevines and fig bushes.

“Burning Oysters Day and Night”

The burning of oyster shells was done in limekilns. In many cases, the kilns were located in wharf districts, in the vicinity of oyster canneries and shucking houses.

That kind of limekiln was usually a tall, chimney-like brick or stone structure that resembled a blast furnace. That kind of limekiln is known as a “shaft kiln.”

Diagram of a modern shaft limekiln. Courtesy, LinguisticDemographer

Diagram of a modern shaft limekiln. Courtesy, LinguisticDemographer

In a shaft kiln, the lime burners burned hardwood or coal in a middle section, and then emptied oyster shells into an opening at the top of the kiln. The lime flowed out the kiln’s base.

J. V. Williams in New Bern, N.C., probably used a shaft kiln of that sort. In 1886 he placed an ad in the New Berne Weekly Journal for “The Best Fertilizer in the World—Lime.”

In the ad, Williams pronounced that his firm was “burning oyster shells day and night.”

Today that seems rather incredible, given how few oysters we have by comparison. However, we have to remember that in the 1880s the workers at Moore and Brady—a cannery at Union Point in New Bern— alone shucked as many as 2,000 bushels of oysters a day.

Once again, I find the availability of oysters in that time period astonishing.

At the time, J. V. Williams was offering lime for a price of $7.00 a ton—I can’t imagine how many bushels of oyster shells went into producing a ton of lime.

Oyster Shells and Lime Kilns

While commercial operators like J. V. Williams operated brick or stone kilns, most farmers and planters probably obtained their oyster shell lime from a different kind of limekiln. That kind of kiln was not a permanent structure and was really no more than a square or rectangular pen built out of green pine logs and boards.

Such a pen’s walls typically rose perhaps 9 or 10 feet high, and the lime burners stacked the pen with layers of oyster shells and firewood.

In that kind of limekiln, the four corners rested on log posts raised 12 or 18 inches above the ground. The burners stacked additional firewood between the ground and the kiln’s lowest pine boards.

This kind of limekiln required a great deal of firewood and was not nearly as efficient as a shaft kiln, but it was much cheaper to build and operate so long as the kiln’s operator had an abundant supply of firewood and an abundant supply of cheap labor (frequently enslaved African Americans before the Civil War).

That kind of limekiln had other advantages as well. Most importantly, farmers could build and operate the kiln on their own land, next to their fields, and could cart the burned shells directly to their fields.

After the shells burned and cooled, farmworkers—in many cases, once again, enslaved men and women— carted the shells into the fields and unloaded them into small heaps spaced as evenly as possible. They then covered the piles of burnt shells with a light layer of earth, which typically proved moist enough to “slack” the lime in a few days.

“Slacked lime” refers to lime (calcium oxide) that has been mixed with water to make the form of lime (calcium hydroxide) that is best for plant growth.

Once the lime was slacked, the farm’s laborers would break down the heaps with broad hoes, spread the burnt shells evenly across the field and plough the fields to make sure that they were fully integrated into the soil.

According to a farmer in southeast Virginia writing in The Farmers Register in 1833, “The quantity applied to the acre is about 70 bushels of the burnt and unslaked shells, which quantity is produced by burning 6 hogsheads (108 bushels) of shells.”

A Core Sound sharpie under sail, ca. 1890. Sharpies like this carried oyster shells up coastal rivers to trade for corn and other farm products. Photo by Wirth Monroe. Originally published in Howard Chappelle’s The Migrations of an American Boat Type (1961). You can find a story about Harkers Island fishermen carrying oysters up the Pamlico River on a sharpie in the late 19th or early 20th century elsewhere on this blog.

A Core Sound sharpie under sail, ca. 1890. Sharpies like this carried oyster shells up coastal rivers to trade for corn and other farm products. Photo by Wirth Monroe. Originally published in Howard Chappelle’s The Migrations of an American Boat Type (1961). You can find a story about Harkers Island fishermen carrying oysters up the Pamlico River on a sharpie in the late 19th or early 20th century elsewhere on this blog.

Making slacked lime fertilizer out of oyster shells was so common in the 19th century that coastal fishermen often carried loads of oyster shells up local rivers during the winter, when they had little else profitable to do. Along the river landings, they sold – or more often, bartered—the oyster shells for corn and other farm products.

Prior to the state’s oyster boom in the 1880s, oysters still had so few markets that Pamlico Sound watermen often raked up smaller ones and, not bothering to shuck them, sold them for a few cents to limekiln operators.

Other Uses for Oyster Shell Lime

Historically coastal people used lime for a variety of other important jobs, too. Fishermen soaked their cotton gill nets and purse seines in lime every day in order to preserve them, and lime was used in variety of other coastal occupations, including tanning, soap making and pickling.

Though I don’t think many scientists would endorse the practice today, lime was also used widely as a disinfectant. It was even believed to stanch the spread of disease.

During the great yellow fever epidemic of 1864, for instance, public health officials in New Bern burned a mix of lime and turpentine dross in the city’s streets. If they were like physicians and sanitary authorities elsewhere, they also spread powdered lime in graveyards.

I can’t remember seeing historical records indicating that North Carolina’s coastal residents used oyster shells to make the lime for these purposes, but I have to assume they did because other kinds of lime were so difficult and/or expensive to obtain especially prior to the Civil War.

* * *

Next time—I’ll look at one more historic use of oyster shells on the North Carolina coast, a use especially important to the state’s farmwomen and their families in the late 19thand early 20thcenturies.

One thought on “A World Built of Oyster Shells

  1. Pingback: Castle Island — Coastal Carolina

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