A Green Portland Cement Alternative, FAQ Friday with Randy Ruth

You might ask yourself… How is Natural Hydraulic Lime (NHL) a green building material? The simple answer would be that it releases about 80% less CO₂, pound for pound when compared to Ordinary Portland Cement (OPC) during the manufacturing process. But why is this so? Well that requires a bit of understanding on the manufacturing of the two very different products.

Both NHL and OPC are made from limestone, although not necessarily the same kinds of stone and are fired in a kiln. NHL is produced in Vertical shaft kilns, which is like a big chimney, with natural gas or clean coal at a low temperature. While OPC is burned in a rotary kiln fired at nearly 2,500 F. The amount fuel used to maintain such a high temperature is by far greater than the relatively low firing temperature of NHL.  Often hazardous waste is used as a fuel, which can emit toxins into the atmosphere. During either process CO₂ is driven off into the atmosphere. Even though NHL production drives off less CO₂, the benefits don’t stop there.

When the NHL is ready to be mixed as a mortar right out of the bag, it’s hungry. NHL wants the CO₂ that was pumped into the atmosphere back all for its self, in its natural process to turn back into a limestone. As different grades of NHL are produced their whiteness and density change. On a scale from lightest to heaviest and from whiteness to grayness, NHL 2 is Light and white while OPC in heavy and grey. Since mortar is mixed by volume in the field, less lime is used per pound to make up the same volume of mortar using OPC.

-LimeWorks.us (Linked-in : Blog : Facebook : Twitter)

Historic Fabric melded with Traditional Mortar at the Irish Hunger Memorial in New York City

Blocks from the World Trade Center Memorial and the construction site of the new World Trade Center sits a half acre patch grass dedicated to raising awareness of the Great Irish Famine. This memorial was under construction on September 11, 2011 when the Twin Towers fell. The memorial saved that day, simply because of the direction the wind was blowing. The plume of dust blew from 1 World Trade Center in just a way that it didn’t touch a single stone, all of which were donated from each county throughout Ireland. Even a 19th century cottage was disassembled in the County of Mayo and re-laid in Manhattan using a lime mortar that was determined to most closely match that of the original. The memorial was dedicated in 2002 by former New York mayor Ed Koch.

A team from LimeWorks.us recently visited the site and put together a collection of images seen below. The names carved in the stones represent the counties of Ireland. St. Astier Natural Hydraulic Lime was used throughout the memorial walls and cottage, supplied by LimeWorks.us. The structure has been holding up very well and we are very proud to have been part of this important piece of built heritage.

-LimeWorks.us (Linked-in : Blog : Facebook : Twitter)

All photos Copyright Sean K Maxwell

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All About Lime Paint, FAQ Friday

Although they date back thousands of years, some of the best examples today of lime paint are those pictured in scenic postcards of gleaming white and pastel colored villages, so abundant throughout the Mediterranean. Many architects and designers currently seek a return to these methods and products of the past. Lime paint changes and evolves as it slowly ages, giving buildings an appealing, provincial look. Additional coats can be added as time goes on, enhancing the depth of colors. Modern paints often seal in humidity, which later leads to peeling and other exterior damage to a building’s surface. More like a stain than paint, lime paint is absorbed into the wall, penetrating the background. Once cured, the lime paint allows the surface to breathe, becoming a peel-free surface as it allows humidity to escape.

Examples:

Lime Paint base, (Natural), has no color added. It can be used to whitewash an old masonry building with only two coats and turn a dingy structure into a “museum-like” historic landmark. This is the Gambrel Roof House in Historic Fallsington, PA.

Before

After

A home in Lambertville, NJ originally had a shelter coat of lime wash put on the soft under-fired brick. #345 St. Astier Lime Paint was used to refresh the building, protect the brick and maintain good breathability for the coating so as not to trap moisture in the wall.

Before

After

A home in Stirling, Scotland which has had the facade restored using colored limewash over a lime/sand render. The home is located along the way up to Stirling Castle.

 

 

 

 

 

 

 

 

The Coastal Heritage Society Preservation Team members of Savannah Georgia whitewashed the retaining wall at the Roundhouse Railroad Museum using St. Astier lime paint.

Before

During

After

A home in Massachusetts originally had a harled finish coat of lime stucco. The St. Astier Lime Paint #429 was used to refresh the building’s exterior look while protecting the soft lime stucco with a “like to like” compatible coating that will wear down over time rather than flake and peel off. The work was accomplished by Florentine Masonry Restoration.

-LimeWorks.us (Linked-in : Blog : Facebook : Twitter)

Use of Traditional Lime Paints (FAQ Friday with Randy Ruth)

This has been a crazy week here in the Northeast. First and earthquake then Steve Jobs and now hurricane Irene is coming for us. But Randy has another frequently asked question to answer today about the use of traditional lime paints.

Q: Isn’t lime paint an old technique for buildings? Aren’t there more modern options that will look better and last longer? 

A: Lime paint or as it is traditionally called whitewash is indeed an old technique for use on buildings, for both interior and exterior use. Lime Paint is made from slaked high calcium quicklime with a greater addition of water than what would be used to make lime putty. The resulting product has a consistency of thin milk.

Lime Paint is used on the exterior of buildings as a sacrificial breathable protective coating over lime render, brick, concrete, adobe, stone and earthen structures. By applying multiple thin coats of Lime Paint, each coat reacts with carbon dioxide in the atmosphere to convert back to calcium  carbonate, also known as limestone. This technology has been around since before the construction of the great pyramids in Egypt, where lime was used in mortar formulations. 

There are some limitations to using Lime Paint in modern times, most likely because of the expectations people have from today’s common latex paints. Although, Lime Paints do wear away, can sometimes chalk when rubbed and cannot always achieve the same brilliance of modern paints , they do have some wonderful properties that make their use appropriate for modern applications.

Lime in of itself reflects light in a such a special way that we get the term “limelight” from its use in early stage lighting techniques. The colors that can be achieved with Lime Paint are more of an earth tone and give off a warm glow that modern latex cannot provide. Since Lime Paint is mineral based it does not peel or flake, it simply wears down.

When a “breathing” wall needs to be protected or decorated with a paint or stain, Lime Paints provide the breathability suitable for the wall. However when a tougher more durable coating is required silicate paints and stains can be used.

Silicate paints are mineral paints made from either sodium silicate or potassium silicate and chemically bond to a masonry substrate, through the chemical act of petrifaction. This allows a paint that can also not peel or flake due to the laws of chemistry, similarly to Lime Paints. Silicate paints were originally made during the mid 19^th century in Europe and have since been refined to become some of the best paint for use with masonry. They can reach a wider range of colors when compared to Lime Paint. Although silicate paints may last longer with less maintenance it does not particularly make them better than Lime Paints.

Someone who wants an “aged” look or even the more natural feel of lime would think Lime Paint is a better choice over silicate. For a muralist who does not want to be bound by a limited color range and needs the durability of silicate in a city environment, then silicate paints are a no brainer. At the end of the day, when choosing a breathable, historically proven paint for a building, one must weigh the pros and cons of each paint when compared to the demands of the project at hand .

 

-LimeWorks.us (Linked-in : Blog : Facebook : Twitter)