Preservation in Process: A Master Mason at the James Brice House

By Special Contributor posted 07-03-2018 15:56

  

Introduction by Ariane Hofstedt and Videography by Mark Hildebrand

Since December 2017 master stone mason Ray Cannetti has been working with Historic Annapolis at the James Brice House in Annapolis, Maryland. His primary focus has been completing forensic work and restoring architectural elements to their original 1774 appearance. The James Brice House account book provides no direct evidence about who did the original pointing work. Whether they were a free journeyman, a master mason, or a skilled enslaved mason, the worker was clearly well trained and had a confident hand.

In an effort to make the brick and mortar replacements as true to the original composition as possible, Mr. Cannetti established a customized onsite process. It involves burning oyster shells in a kiln for more than eight hours to make mortar, analyzing the original materials, finding local sand that matches the original in color and texture, and slaking—mixing the lime and sand for the mortar and letting that mixture rest. These videos depict this process step by step and include Mr. Cannetti’s thoughts about the process as well as about craftsmen then and now.

lime-rick-17_BriceHouse.jpg
A lime rick in the process of burning shells for mortar | Credit: The George Washington Foundation

Burning Shells

Transcript: It’s all about what’s available. In the Chesapeake, when they’re first, really, arriving and considering colonization, one of the things they found was there were no readily available sources of limestone. The thing[s] that there were, was many, many, many, shells. We have oyster shells, clam shells. We have shells that we have actually burned at the Brice House. We’re not burning our shells as they would have in, what’s called an open-air kiln, or a “rick,” in the 1700s. We’re actually burning our shells in a modern ceramic kiln.

You have to change it chemically. By super-heating it what you’re doing is you’re driving off an oxygen molecule. So, it converts from calcium carbonate to calcium oxide.

Digestion Analysis

Transcript: For our process, the way we do it, we start by a mortar analysis. And by this mortar analysis—it’s called “digestion analysis”—we break down a mortar sample, specifically weighed sample, and it tells us how much lime and how much sand was in this mixture. It gives us a proportion.

Local Sand


Transcript: Luckily, we were able to find a sand that matches the sand in our sample over at the Carroll House. It’s probably the only surviving section of undisturbed shoreline in Annapolis. We went over there, and we took a small sample of the sand and matched it against our sand that we had broken down from our digestion mortar analysis, and it’s an exact match.

Pointing


Transcript: We’ve just finished reconstructing a wall in an opening that was put in here in the early 20th century. “Pointing” is a masonry term. When we’re doing our pointing, we’re also trying to match what was done originally. So, we look closely at the original mortar joints and how the workman’s tooling them with his trowel, and we try to imitate that to the greatest degree possible.

We’re constantly evolving and trying to get better, improving on what we do. And that’s a lot about what we’re doing here, with the idea that we’re actually burning shell on site, to make our mortar with, to the idea that we’re actually finding a local location that we’re getting our sand from. Again, you know, it adds to the authenticity of what we’re doing.

The wet mortar, you can see the difference in the color. When the wet mortar does eventually dry, it is going to be the color of the pointing that we’ve done already. Again, you know, we really do try to imitate the original to the greatest extent possible.

If you look at some of the pointing we’ve done already, you can actually see the point of the trowel as he’s pushed it in there, and you’ll find the same thing in the original pointing. Over here, which are our areas of original pointing, you can actually see the point of the mason’s trowel, and you can tell as he pulls along the mortar joint to smooth it down.

Slaking

Transcript: Slaking is the breakdown of calcium oxide to calcium hydroxide. The Romans were doing it, the Egyptians were doing it.

In our digestion analysis we work out proportions. And from our proportions we know that they had two parts of burnt shell to one part of sand. Yeah, making early mortar is not much different from baking. To speed up our reaction, we like to use warm water, because it’ll end up being an additional catalyst in the reaction.

Steam

Transcript: Okay, now let me go ahead and add the water. See they’re going off already. The great thing about doing it this way is that it’s very efficient—we don’t have to slake the lime and then add the sand to it. Everything’s happening in the same pile. So once the reaction’s happened and we’re ready to make mortar, all we do is cut off a section of it and then mix it up and use it. That’s going off right now.

Now, it’s important to cover the pile of shell and sand to ensure that you get thorough slaking. In a lot of ways what we’re doing is we’re creating a primitive autoclave, where we’re capturing the steam that’s being created by the reaction of the shell with the water. This steam will permeate all the shell, so it will get all of it to break down to the greatest extent possible.

Slaking Completed

Transcript: What’s happening is all this heat is from the calcium oxide, and it’s trying to get back the oxygen molecule that it gave up when you fired it. So it’s actually getting a hydrogen molecule right now, and then everything else is steam.

When the lime slakes, it actually doubles in volume, and you can watch the pile expand as it’s slaking.

Workers of the Past


Transcript: We often think about the men doing the work before us. Every mason has his own technique. All workers have this sense of pride in their work, and it’s always related to different skill levels. It’s interesting for us, walking around here because we can look at sections of wall and we can say, “Well, gosh, this guy was a very accomplished mason. All this work is very uniform, and neat, and faced really well.” And then we’ll see other sections that haven’t been done with as much care. And, it’s interesting to see that because it gives character to it. And it tells us a lot about, you know, the people doing the work. Because often we wonder about how our work is going to blend into the original work. And what we come up with is, “Well, we’re not much different than the guys who did the work originally.” We’re the same way: we have a certain level of expertise that we like to put into our work, and that work has now become a character of that wall.

Ariane Hofstedt is the executive vice president of Historic Annapolis. The videos were filmed by Mark Hildebrand of Make Your Mark Media and transcribed by Ianna Seebachan.

 


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