How Lime Mortar Traditionally Got Its Color and How We Can Replicate This Today, FAQ Friday with Randy Ruth

Seven factors that can affect the color of lime mortar in no particular order of significance, Lime, aggregate, pigment, water content, rate of absorption, original surface texture and erosion.

By its self, the color spectrum of lime can vary from bright white, light grey, slight pink or ochre colors. This color is dependent on a few factors such as the original stones chemical makeup and burning temperature. When an appropriate limestone is thoroughly burned (calcined) at a particular temperature to produce hydraulic or non-hydraulic quicklime and then hydrated to produce either a lime putty or dry lime hydrate, the result will be a white or off-white color. The first factor affecting the whiteness index of the lime will vary depending on the raw mineral impurities in the limestone. A limestone with a higher calcium content with all other factors aside will produce a whiter hydrated lime. If that same limestone is burned at a slightly higher temperature, the result will be a slightly grayer hydrated lime. Although, lime plays a role in the final color of a mortar, its significance today, when replicating a mortar joint is minimal, often due to the lack of availability or technical characteristics like Hydraulicity.

Aggregate has a huge effect on the color of lime mortar. Historically aggregate for masonry mortar would be sourced from either local sand beds, found near creeks or rivers, or from the trimmings of stone on site and possibly brick pieces or dust as a pozzolanic additive. The larger screenings of the aggregate play a role in the overall tone of the final mortar color but it is the fines that do most of the work. The smallest particles in the aggregate AKA fines will give the biggest impact on the final color. Brick dust, limekiln dust and clay impurities are pozzolanic fines that can be found accidentally and at times intentionally accompanying the aggregate. Today these impurities are almost never allowed into a replicate mortar mix, as the resulting technical data from such a mix design is often cost/time prohibitive for a project even if historically appropriate. As a result powdered pigments are often used today to achieve a particular mortar color.

Just because pigments are predominantly used today in mortar mix designs, doesn’t mean that they weren’t used over 100 years ago. Colored mortar is an important design element in any building of today and yesteryear. The types of pigments used in mortars have not changed all that much in past few hundred years. Iron oxide, carbon black, and natural ochre’s hold a solid footing in the industry today, each presenting their own limitations.

It has been proven that carbon blacks can fade dramatically over a 30 year period in masonry mortar. Even though their tinting strength is very good, if not controlled carefully  shades of grey can be very difficult to achieve. Natural ochre’s can produce wonderful colors and be very accurate when making accurate replicate mortars. The problem is in their tinting strength, and consistency in production on a large-scale. It may take above a 10% dosage of natural pigment to achieve the same color in a mortar using iron oxide pigments conforming to ASTM C979. Because of their durability, tinting strength and quality in production, iron oxides have been deemed the best pigment for coloring mortar on a large-scale.

Even when using appropriate pigments at the correct concentration, water content in a mortar plays a big role in determining final color. Using the same exact mix in two batches and varying the water content by 10% will produce a significant change in color. From experience, I have noted that this problem is most evident when trying to achieve a red colored mortar. Light grey’s can also be problematic but are less evident and are usually deemed acceptable. That is why it important to measure all ingredients in a mix carefully to ensure consistency from batch to batch.

The practice of mixing mortars consistently should carry over to pre-dampening of masonry units. By pre-dampening consistently as possible, the rate of absorption is controlled. This is a good practice just so mortar will not reach a flash set, and to control curing of the mortar which plays a role in the final color.

There is some debate on how a replicated mortar should look when not replacing all the mortar. Should it look new, with a smooth surface that stands out because of the way light reflects off two different surface textures? Alternatively, should it blend in with adjacent mortar joints? Personality, I believe in the latter. If a new mortar is inherently the same color at its core as the old historic mortar, than even though a slicked smooth replacement mortar will eventually blend in it can still distract the eye. A good repair for just about anything should be as seamless as possible. Besides, won’t a different texture erode differently, resulting in the continuation of a miss match over time?

This brings me to erosion in mortar. As a mortar erodes, the color of the aggregate begins to come through. This color can sometimes throw off the human eyes perception of what is the color to be achieved when color matching. Someone explained this to me so well once that I must share. He had asked a room full of people what the color of foam on the head of a beer is. All replied white in color. We all got it wrong. The answer is amber like the color of the beer. This is because of the way light is reflected back to the human eye off a larger Surface area. Now that is in extreme case of a dark color turning lighter but the principle is still applicable to mortar. However, in most cases the rougher the color the darker a mortar is, and depending on who well the color of the sand is matched, you may just get a replacement mortar that will be seamless for generations.

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

Lancaster Central Market Wins Pennsylvania Historic Preservation Award using Natural Hydraulic Lime

Congratulations to the city of Lancaster and Hammel Associates Architects, LLC. They were recently awarded for the restoration of the Lancaster Central Market in Lancaster, PA. Located in the middle of downtown, this space has been used as a market since 1730 and is said to be the oldest continuously operating farmers market in the country. The market structure was designed by architect James Warner and constructed in 1889 of locally produced red brick on top of a brownstone base. The market was named one of America’s top ten “Great Public Spaces in America” by the American Planning Association in 2009.

Many efforts were made in the recent rehabilitation project to restore the market’s elements including the original windows and doors. The damaged bricks were replaced and the building was repointed with Natural Hydraulic Lime 3.5 and deGruchy’s Ecologic® Mortar provided by LimeWorks.us  as a complementary mortar to the original lime mortar of 1889.

These appropriate historic restoration techniques worked to bring the market back to its original glory for the enjoyment by generations to come.

Andy’s Podcast Interview with the National Center for Preservation Technology & Training on the Role of Lime and its Continued Importance Today

Andy deGruchy of LimeWorks.us spoke with Jeff Guin the National Center for Preservation Technology & Training recently on the role of lime in historic architecture and in preservation, as well as in new green construction. Andy has over 30 years of masonry experience working with historic structures throughout the United States and abroad. He has been published in magazines and books sharing his knowledge of the historic application and current techniques for the use of lime mortars, plasters and paints.

Download this episode as an mp3 or Subscribe via iTunes 

Transcript:

Jeff Guin: Tell me about a few of the structures that you have worked on.

Andy deGruchy

A. DeGruchy: We’ve worked here in Pennsylvania with my other company, DeGruchy Masonry & Restoration, for the last 27 years we’ve been restoring brick and stone buildings.  Some of those have included work at Hope Lodge, Daniel Boone’s Homestead,William Penn’s Homestead,  James Hobin’s (architect of the White House) memorial in Mt. Olivet Cemetery in Washington DC. Also, a myriad of historic Victorian homes, farmhouses in Bucks County, Pennsylvania, where I live and all sorts of accoutrements, smokehouses, and summer kitchens and basements–some not-so-glorious buildings, but just a lot of hard work in the maintenance using appropriate materials to fix these vintage structures.

JG: So do you primarily work in the Pennsylvania area and the northeast or do you travel to other parts of the country as well?

AD:  Well we’ve concentrated our work within about an hour and a half driving radius of where I live and where my shop is in Quakertown, Pennsylvania.  However, we’ve done work as far as Florida and consulting work on the use of our materials as far as Puerto Rico and Maine out to Oregon and all over.

JG: …and to Nashville, I know, because that’s where I met you originally at the NCPTT Nationwide Cemetery Summit.  Are cemeteries something you work on frequently?

AD: We do not do a lot of cemetery work ourselves, although I did mention I restored the architect to the White Houses’ James Hobin and his memorial  in Mt. Olivet Cemetery, and dotted throughout our history, there has been some work on statuary and memorials.  But my connection with cemeteries has been at the prompting of a conservator and professor at Columbia who saw our laboratory and the work we are doing and said, “you know, you are the best kept secret, you really need to step up to the plate and tell the world that you are here,” and that is why we are even doing the radio interview now trying to get the word out that we have some great resources.

Understanding Lime Terminology

JG: Taking that a step further, there is a lot of confusion around the terminology related to lime mortars and specifications.  I wonder if you could break some of that down for me. Talk about the different types of lime and the differences between historically accurate lime as compared to the improved or modern types.

AD: Yes, that’s a very good question, and it is a little bit of a peeve with me because, you know, really lime is lime is lime and has been the same raw material from the beginning of time until now.  Nothing has changed, but a lot of smoke and mirrors and confusion puts the end-user, building owners, architects, engineers, and masons in a state of confusion. Really, it is a very simple thing to understand:  That is, lime has always fallen into two categories; it’s always been pure high calcium, 98% pure lime.  When I say lime, I do mean the shells and bones of marine life that build up over millions of years without any impurities in it.  If it was 98% pure, just comprised of that, then that is called high-calcium lime and then it falls into the second category, which is impure lime.  Now we designate that into a breakdown of two areas.  One would be dolomitic, which would have a smaller percentage of magnesium and then a magnesium lime which has a larger percentage of magnesium.

We look at ancient structures throughout the world, a lot of materials scientists will study them and say, “let’s not look at what is broken about this building, let’s look at what’s working so well that it is still here after 500 years.”  They will find common denominators. And with the mortar, they find that the basic rule in masonry is, you never can fight water and win.  Water will always win in the end.  So, the mortars in these ancient buildings had a lime and sand composition that would help to process moisture out to the atmosphere again.  It would not trap moisture.  Had it trapped moisture, or reacted with sulphates and other negative reactions, then the demise of the structure would have been accelerated, and it would not be here 500 years later.  But they found that when you use a lime that is a catalyst of processing water back to the atmosphere, now you have a symbiotic relationship with nature and with water.  Therefore, you are now not in conflict with nature, but you are going to survive because you found a way to get along.  The way that it does get along is that when the limestone, which could be a block of this sediment that I mentioned, is burned, it is the one stone that when you cook it for 48 hours, maintained at between 1,650 to 2,000 degrees, you will push-off the carbon dioxide content in the stone. In doing that, after the stone has cooled, it weighs 44% lighter than it did when it went into the kiln. When you reintroduce water to it, it will violently take that water in what’s called slaking–like slake your thirst–and it will boil the water it sits in within a 10 minute period.  However, a little known fact is that if you look at that same mortar now that has been made with that lime putty and sand has been added to this putty that has had the water reintroduced to the limestone, you can go with a future 10 years, 20 years and 30 years and the lime is always slowly converting back into a limestone again through carbonation. It violently draws carbon dioxide out of the slaking bath at first, and it is a young buck at that time. But 5 years later, 10 years later, 50 years later, it is still trying to convert back into a limestone and will always draw carbon dioxide out of the air. So that is the symbiotic relationship again with nature. When all these nor’easters and wind and water blow on buildings, they are delivering carbon dioxide and the lime mortar joints are hydrophilic. So these walls that get saturated actually give up their water towards the attracting lime mortar which then says, “can we have that carbon dioxide from you because we are still converting back into a stone” and then releases the rest of the vapor out to the atmosphere. So this dynamic that has been going on, which material scientists have come to understand, is something that has preserved historic fabric. Because no longer does the soft sandstones and bricks that had they had the wetting and drying cycles go through there, faces would have exfoliated and been damaged. Now the historic bricks and stones give up their moisture to the hydrophilic in attracting lime mortar.

When the Romans who were famous as architects and builders, they burned lime at this time-honored temperature to maintain the reactivity of the lime between 1,650 and 2,000 degrees, it had the ability to convert back into a limestone. However, today’s modern production dead burns lime and in many cases and over-cooks it. When you say to the lime that you can get it at any hardware store available in the country today, and say well, I’m going to add water and sand to you, I’d like you to convert back into a limestone and become as hard as hopefully you were at one time as a stone: that inert dust can only be used for adding plasticity, a flow-ability to a cement mortar or controlling the setting time of a cement mortar.  The majority of the available hydrated dolomitic Type S hydrated lime in the United States has just sand and water added to it as a stand-alone binder. It does not have the ability become as significant and durable as the historic mortars because of the burning temperature.  So the problem–although there is only two kinds of lime in the world and always has been–the way the lime is cooked has been changed in that it is being sped up for the process of production because the key elements it’s only asked to do today is that plasticity and control of setting time of a cementitious mortar.  We have personally not had any success with using a Type S hydrated lime and adding sand and water and then putting it into service as an exterior above grade mortar in extreme free stall cycles like the northeast, mid-Atlantic states where I am from.

The limes to reproduce historic mortar when we work at some local building, someone might say, “Are you going to go build a kiln and find local lime and reproduce every element as it originally was?”  Well, the cost becomes a problem, so we import the natural occurring hydraulic lime, which is pure high calcium and evenly dispersed silica so that we know when we add certain percentages of sand, we are going to get a final result that is going to have a known value for liquid and vapor permeability, PSI strengths … So it is true that in the United States and Pennsylvania, maybe these historic structures were not built with French hydraulic lime but it is a suitable replacement that pound for pound and cost-wise, is reasonable and we are putting in an in-kind replacement that will do no harm.

New Uses for Lime

JG: Do you see lime being used just in historic applications or are there new applications for lime now?

AD: We have a 100,000 bag order for a tropical resort that we are creating a lime for a green build.  Because, as I mentioned, the mortars that we have used for historic restoration, our intent was only to use them to do an in-kind replacement like-to-like–instituting no material that was going to cause an associated damage to historic fabrics surrounding the stone or brick, you know, like the window frame or something expanding and damaging because of what we used.  However, as I mentioned about people from the cemetery, conservators and fine arts finishing people–we’ve also found that it really meets the criteria for gold and platinum LEED credits. When you are trying to lower the embodied energy, the building of what has been used by reclaiming and recycling, you know, existing post consumer material and getting all sorts of energy advantages in improving indoor air quality, they find that the lime just to begin with–because there is 7,500 years of building history proving that it works, where modern cements although introduced in the 1870’s in the United States, in my opinion did not fully take hold until after WWII.  So the window of time where cement absolutely dominated for all veneer mortars and building and stucco and everything, came like 1945 until now.  But the embodied energy to create a pound of Portland cement, which is the binder for modern stuccos and brick laying mortar and stoneware is incredibly high.  Matter-of-fact, I believe the efficiency is very low because there is more waste than there is usable product.

Making Lime Repairs

JG: Now lime mortar does have to be re-applied occasionally because it does work with the environment.  How often does that have to be done?

AD: Well there are many historic structures that are in the United States that are only just receiving their first re-pointing.  So, in the Philadelphia region, the area where I am from, we will see a historic building that you know, maybe was re-pointed in the name of preservation and maybe under the guidance of some government agencies and done only in the 1980’s, and yet it has to be re-re-pointed and it had a Type O or high lime content mortar with a little Portland cement added.  Yet, the 200 year old buildings in this region (down the street from the one fixed in the name of preservation) we will find that sometimes these buildings are actually in better repair.  What my goal was originally was to import lime from France and do the things that we were doing was kind of pursuing excellence and saying you know, if there is the concept of getting a 100-year fix because we see that these buildings are 100 – 200 years old and no one’ s re-pointing them.  They did not have the budget to fix it and it is in better shape than the one they did have the budget to fix. Maybe we should try to mirror the properties of the original material.  So, I would say that if a lime application is done appropriately, there is no reason–just like you see in Europe, old plaster over stone, brick and stone buildings or pointed buildings and no one is touching them for 100 years–there is no reason why you won’t get a 100 year life cycle if the project is done correctly.

JG: Is using lime mortars and re-pointing something that everyday people can do or is it just something for the experts?

AD: It’s all dependent upon the skill level of the individual.  So, we’ve met homeowners who do better work than some masons that we know and then we know young masons that their skill level just comes right out.  So what it comes down to, just what pointing is. It is not rocket science.  It’s just binder and aggregate.  It’s sand and lime and then it’s just placing that between bricks and stones but as you know and many who have observed historic buildings throughout the country, they will see blaring examples of bright white mortar that did not match the texture, the tooling, the color of the surrounding area and you have to wonder what were they thinking when they did that pointing job or built that wall like that and to this day, I still do not know what they are thinking but it is everywhere.  So, I think it boils down to not that it is so hard to do, but is someone willing to take the time and care for the project. That being said, some of our best customers, the ones who we love to work with, who are just savvy homeowners who have done their own research, they concluded what they wanted, how to do it, they will take a class and then they will take the time if they are going to do point the whole home, they will commit themselves to: “I’m going to do maybe one square foot but I’m going to do it right.”

Ian Cramb

JG: Tell me about Ian Cramb.

AD: Ian Cramb is a great man, 83-year old Scottish stone mason who lives in Bangor, Pennsylvania. He and his family have been steeped in stone masonry since 1750 in Edinburgh, Scotland and along the way. I think the common denominator of all these craftsman and artisans is love for the trade, and that caused him to assemble a book back in 1992 called The Art Of The Stone Mason.What made it very popular was in it, you could see the love he had for the trade and just carefully sketching out details describing how to cut a stone or how to build a stone arch or naming parts of a wall. All these things were very popular with masons because it was a throwback to how masonry had historically been done and those details again that is a common denominator that is going to make the outcome of any project become excellent and last for the 100-year fix.  So, he began to develop a following of people in stone masonry and I being one of them, bought his book years ago and then of course he is local and I touched base with him about some things and became friends with him.  Next thing you know, he had to get all the information together for his second book, which is The Stone Mason’s Gospel According to Ian Cramb.  As we drove along one day while on some projects we were building, he said, “You know, I can’t finish my second book and it’s all your fault,” and I said, “Well what you mean by that,” and he said, “You know, in all the conversations we have regarding the lime, you really have a better handle on the technical aspects and how to explain it than I do and I want to put that in this book.”  So he asked me to edit and read through his book and understand what he is writing, then put some information that is going to clarify lime.  So I helped him produce this second book with my computer science major son who is in college, to produce the book on the internet and we produced a few hundred copies and we have them now actually on our website for sale and that is The Stone Mason’s Gospel According to Ian Cramb.

Sharing the Knowledge

JG: So you kind of see it as part of your job, your responsibility, to pass the knowledge along; to make sure that people understand not just why it’s important but what the history of lime mortars is.

AD: Yes, very much so.  I think that there was a time when masons would of course hide the trade secrets.  They had their mason marks and they would mark the stones that they produced and shaped and dressed and they got paid piecemeal that way and some of the ancient trade secrets that sort of trail off into the Masonic tradition of the non-operating masons.  In today’s masonry, as we know, all our buildings are accelerating in degradation and as the buildings are getting older and older and fewer and fewer people are going into the trade, it has been my position to say there is no more time for trade secrets.  If anybody wants to know a trade secret we are glad to share it because it just does not seem like anything that resembles close to actually doing physical hard work, is not getting much of an audience of young people wanting to get into it.  However, those who do get into it, find it incredibly rewarding and then ask themselves, what was I thinking, I was going to go to college and I was going to be stuck in a cubicle somewhere, so  I am very much in favor of disseminating knowledge, giving it away, but I see a lot of exploitation of historic resources for the sake of personal gain by keeping a patient sick and not getting in there and putting in a repair that would give a long service life, and so I am totally opposed to that and I want to blow the blinders off of that thing and I want to shed as much light on these subjects so that we can move on with the good and excellent conservation of our nation’s historic resources.

JG: Andy thanks so much for being on the podcast.

AD: I’m glad you could include me and hope that it was informative.

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

NCPTT original post

Burning Lime, the Traditional Way

This is an incredible video that really shows the difficulties of burning limestone the old way. Stacking wood, limestone and coal in an old kiln these men go through the process using traditional methods to turn regular limestone into caustic burnt lime.

Saucon Valley Historic Pennsylvania Barn Tour

This past Saturday was the Saucon Valley Conservency 5th annual Historic Barn Tour. The day started off with a presentation at the Beethoven Waldheim Club by Robert Ensminger and Gregory Huber on barn types and styles found throughout Saucon Valley and the Shenandoah Valley. Following the presentation, we all embarked on a self guided tour of 9 historic barns dating back to the late 1700s and early 1800s. Guides greeted us at each barn and some of the homeowners were even there. Many of the barns had been passed through their families for generations. It was amazing to hear some of their stories and see these magnificent barns, all uniquely built with influence from many European countries.

The first barn we visited was converted to a house in 2005 and is now a home full of remnants of the past. The husband is an auctioneer and has filled his home with local antiques from regional dairies and other businesses of yesteryear.

The other barns were all unique, and it was very exciting to see all the small differences. On one barn, the interior was in excellent condition and still covered in the original hot lime with the solid white lime nodules.

Here are some of the best photos of the tour, please take a look.

all photos ©Sean K Maxwell

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

Bob Vila- Using proper Lime Mortar is Important!!

This is an excellent video explaining some of the historic techniques of using lime mortar as well as some tips on how to properly repair a damaged historic building. Also, see how you can analyze your own historic lime mortar and see the original sand that was used in the construction of your building.

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

 

All about Lime

This is an excerpt from The Stonemason’s Gospel according to Ian Cramb written by Andy deGruchy, an explanation of lime.

Lime

Limestone, the material calcium carbonate, has never changed from its beginning up to and including now. There have always been two classifications, ‘pure’ and ‘impure.’ Today it is classified as pure (high calcium) and two levels of impure lime based on the magnesium content, Dolomitic and Magnesian.

What has changed over the course of time, especially in more recent years, is how the calcium carbonate stones have been prepared by firing them in the kiln to produce quicklime. There is a most simple way of burning limestone in a vertical kiln using wood for fuel and keeping the temperature between 1650F and 2000F and then cooking it slowly over a few days. This has been done for centuries.  The proof that this method of cooking the stone has extreme merit is evidenced by the very old buildings throughout the world which still stand that utilized this method of preparing lime. ‘Lime’ is what limestone is called when it is cooked and slaked to make a putty that is incorporated into making building mortars, plasters and paints. The technical chemistry was unknown to old lime burners and masons. They just knew what worked and kept using the time-honored methods of preparing the lime.

When burned limestone has water reintroduced to it, called slaking, it then blooms into a beautiful white putty-like material. The volume of putty produced is double that of what was once the condensed rock. This ‘lime putty’ will draw carbon dioxide out of the air for a very very long time and slowly convert back closely to a limestone again. Lime putty has its initial set over a six week period by exposure to air. However it will attract carbon dioxide almost to a point of being completely ‘carbon neutral’ over time in regard to the embodied energy first required to produce the lime.  Through lime’s interconnected pores it even knits minor fissures together by moving about some of the not fully burned ‘free lime’ which creates more surface area to draw in the carbon dioxide.

Early masons knew that some limestone deposits produced limes that set quicker and became harder sooner. So, unlike simple air-setting lime putty, hydraulic limes were used throughout the world and in the United States to build with when the impure raw material had reactive silica or certain clays naturally found in the stone. These impurities were cooked along with the calcium carbonate stone. The term ‘hydraulic’ means to set with water and under water. Portland cement is hydraulic lime. The reason it is overall strongly suggested not to be used for masonry building conservation is that the synthetically added materials used to make Portland cement become intensely hydraulic also make the whole lot detrimental by various degrees of incompatibility with original porous building components. Two of those detrimental characteristics are that Portland cement is brittle and does not accommodate movement and secondly it reacts with sulfates. But a great incompatibility and detriment to historic masonry buildings is the increased densification of mortar that consequently occurs with every increment of additional Portland cement added to make the mortar become very hard. Densification does not allow the building to remain ‘breathable’ through the mortar joints but instead allows water to become held back and sometimes trapped into absorptive inner bedding joints. This phenomenon forces the wetting and drying cycles of the building to occur through the porous historic units and this is what greatly contributes to accelerated deterioration of the irreplaceable bricks and stone used to originally build a building.

In Ian’s first book he used and suggested mortar mixes that I and every other mason has typically used. These mixes gauge-in some Portland cement into high-lime (Type S lime) containing mortars. The reason we all did this is because readily available Type S Hydrated Builder’s Lime and cement were what we had to work with prior to the commercial availability of natural hydraulic limes now sold in the US. If Type S lime was blended with sand alone we discovered it would not hold up to the freeze-thaw cycles in northern climates. Why this occurs when nothing has changed about the limestone itself puts the spotlight on the cooking procedures. Too hot and too fast of a burn can cause the limestone to become ‘dead-burned’ and loose its ‘reactive’ nature which allows it to closely convert back to a hard and durable limestone again. A durable mortar made from reactive lime which maintains vapor permeable pores and has a desired malleable nature to accommodate minor building movement is the best for vertical, above grade work. Pure air- setting limes that remain reactive because they are burned at a low temperature can be obtained in the US too. However, due to the six week set time the cost for building with these limes goes up exponentially. So in this book the mortar mixes are more clearly defined from Ian’s first book as being mixes that use a binder of hydraulic lime but not the hydraulic lime that is Portland cement. I hope this helps you in designing appropriate mortar mixes for certain corresponding applications. It is a labor of love and worth understanding in order to realize the greatest long-term service life which can be obtained for repairing a vintage building and its components. I hope my contribution of this knowledge into what makes one lime better than another brings about a higher degree of excellence in the historic building conservation work you endeavor to do.

Sincerely,

Andrew deGruchy