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Sand and Cement

Stucco and Mortar
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One of my earliest memories was crouching down next to a cobblestone retaining wall and inspecting the mortar. Then my playmate, we will call him not-Rudy for convenience, from above on the retaining wall, dropped a rock on my head. Nearly 60 years ago it left an impression, and I imagine that I can see that mortar joint as clearly today as then. A few years back I went to look at that wall, and the stone wall up the street from there that I built some 40 years ago. The walls are still there. For me they both hold memories.

I grew up in the Finger Lakes region of NY State and was raised on top of a hump in a glacial moraine that besides being full of stones was attractive to lightning from the embedded iron in the earth. The furthest most reach of the Appalachia’s, all different from any other place in that geographic region. I spent many days in the local crick playing with stones, building dams, diverting water, digging blue clay and leaving it out to dry in the sun to bake turtles. I enjoyed cultivating pools for the minnows and water striders. The crick was also where I learned to socialize as my friends would come to play and we would build in the water together.

Our driveway was made up of a round gravel of an assortment of stone. I spent many hours, days, out on the back stone wall, the walls that my mother had built, with a hammer crushing the pebbles into sand. I sorted the different types, the colors, and the texture of the crushed stone, now sand into baby food jars.

As an adult one time I stood with an architect at the entry to a Sloan Kettering building in Manhattan and I asked them why their specifications for stone repair were all written as concrete repair. They asked me why I asked. I pointed at the surround to the door and said, “Because this is limestone.” “How do you know?” was their reply. At some point we just do not know what to say. At some point we simply do not know how we know what we know. Then there are those places where we suddenly realize that maybe we do not know at all.

I’ve been around out on the streets of Manhattan sifting sand. I got these sieves off of Amazon, they are made in China, they come in a wide assortment of gradations, they are cheap and if you have the patience they work pretty well. It takes a few hours to shake the 5-gallon bucket to get enough finer sand separate from the coarse to do what we need to get done. People that walk by make comments, like that I look like a gold miner. I respond, “I am getting paid to do this.” But deeper in the back of my mind I have a good day doing this simple action that I have been doing off and on for decades.

The problem comes up though that we have been doing this fairly elaborate stucco job on the lower façade of a townhouse and between what I know, and what I don’t know, I keep running into a wall of what I don’t know. 

As Rudy says, “Oh, you know how to get into trouble too.”

Stucco in a sense is like a thin smear of mortar, the same ingredients that would hold a stone wall together, but in the case of stucco needs to hold itself together as a surface against a field of masonry (in most cases). In this project we need to make a new surface that will match to a surface that is presumed to have been created 50 years ago. We need to provide new shapes, rustication (lines indented to imitate cut stone), and curved bump outs, and to match color. For color we are dependent primarily on the match of the sand. A specific sand that we purchase in New Jersey where we drive out to pick it up. It is several times more expensive than the sand one would purchase at Home Depot. But the sand alone does not a color make. We also need to play with the cement, in this case, contrary to the perspective of our traditional mortar friends who would prefer to play with lime or natural cement, it is Portland cement based, as is the original. The final recipe includes just a tad of inorganic color added to a mix of white non-staining and gray Portland. The color we purchase off the shelf from an artist’s tint source.

I made 20 mock-ups in search for the perfect match, pushed to the left and then the right with each step, until I realized that number 14, that I had at first rejected, had changed color over time. This is how we get to the desired result, but it is also how we get ourselves in trouble.

Stucco, mortar, what people who do not work with it, those who only see the end result, do not often realize is a fluid material. You mix up the dry ingredients with water and then you apply it with a tool, usually a trowel. Once it is where you have put it you go away and come back and it is either where you put it, or maybe somewhere else. It is also now hard, as they say, hard as a rock.

The trouble is the movement, not always intentional, not always from carelessness or disregard but simply that stuff happens. Mortar, like concrete, sags. More stuff happens when you take in the environment, tough summer days at 98 Fahrenheit, days of unexpected rain, direct sun or no direct sun, or old-man cramps in the hands and legs. So, there is one layer applied and as that morphs from the wrong color to the desired color you fill in here or there, and that new in-fill is the wrong color a tad off from the previous, and you nudge and fiddle with the surface until it properly looks like hell. But if you go away and come back it all mellows out. Patience. Trust in materials science. Worry.

If the above seems complicated we can make it worse.

In order to match to the existing color of the stucco on the façade we need to etch the new stucco in order to expose the color of the sand, and to reduce the surface area of the exposed color of the cement. Keep in mind, we are not cleaning the masonry, we are acid etching. In this case we do this with muriatic acid. It is a delicate process, not particularly pleasant, and a total pain. It requires patience and a close observation as the acid foams up and eats away the cement. Caution in handling acids, and despair when it runs down the face of the building and we need to grab the hose real quick before it etches elsewhere than intended.

It is also a problem to control the process. If, in application of the stucco one pressed and swiped in one spot with a bit more pressure and gusto than in another, the stucco being applied by hand, then when it comes to the etch some areas have more cement at the surface than others. Some areas have less cement and get eaten away and made rough with the exposure of the sand. The acid etch reveals a whole other layer of hand activity than if one were to simply apply the stucco, smooth it over neatly, then leave it alone for 50 years.

In the process of this project it occurred to me that the mechanics who did the original work probably did stucco, and nothing but stucco every work day for 15 years before they perfected their craft. People come along and tell us how good it looks and that nobody does this anymore. We tell them that we don’t want to do it anymore either. Here I have a few months to try to imitate the past trades, but what we are to do to this wall is not what they did. What we have to do is quite different and not anything that the traditional mechanics had to even think about.

I tie all of the above in with reflection on Rudy’s search for tools in Myanmar in his blog prior in the series to this entry. A portion of his and Laura’s adventure is to reach out into the unknown of the historic past and meet it up with realities of the unknown present. For me, at this time, that exploration of the unknown is within an hour from home.

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