Brian, While nobody has managed to get access to what I am told are the still existing Corps of Engineers records regarding construction of each of these forts, we need to distinguish between theory and reality. The only way to get an accurate grip on reality is to let the forensic record speak for itself. Of course, that presumes that the mortar is analyzed competently and honestly. There are, unfortunately, examples of analyses that are neither competent nor particularly honest. As an example, mortar samples from Fort Jefferson (Gulf Coast of Florida, 70 miles off Key West), sent to a Scottish lab with close ties to the hydraulic lime industry, came back suggesting it was lime with some sort of hydraulic component, and recommended (surprise, surprise) hydraulic lime. A later analysis by an independent lab with no ties to any manufacturer contradicted that conclusion, finding that there was no lime whatsoever in the mortar, just natural cement and sand. But I digress. The point is that we can presume any nothing number of things, but presumption is a poor basis for deciding what to use in restoring/maintaining these structures. We need to let an accurately determined forensic record speak for itself. As for the thinking of the day, my sense of it is that the engineers who designed and built these structures considered lime inferior not just in strength, but in weather resistance and durability. We have seen a number of examples of multi-wythe masonry structures in which the inner wythes were built with lime and the outer wythe with natural cement. Another common practice, particularly in some lower-cost industrial structures, was to build with lime and then immediately rake back the outer half-inch or so and point with natural cement, to make the building more waterproof. If mortars are analyzed without knowing of that practice, one could incorrectly presume that the outer layer of mortar is harder, recent repointing, and that the underlying lime constitutes the entire original fabric. There are a multitude of other clues into the thinking of the day. Py sent me documentation he found of complaints from the builders of the Gulf Coast forts, about the delays in getting shipments of natural cement from Rosendale when the Hudson River was frozen. They waited. And Ken has learned that when a commander in Pensacola tried to substitute lime for natural cement, Corps of Engineers Chief Engineer Joseph Totten threatened him with court martial. These were purposeful decisions, and each decision to use natural cement was also a conscious rejection of cheaper, easier-to-get lime. These decisions have been supported by the performance history. An architect in Mississippi, working on hurricane damage repairs to some of the Gulf Coast forts wrote me to observe that the portions of these forts built with natural cement and hard Yankee brick before the Civil War were in far better condition than the portions built by the Confederacy with lime and local brick, once the war started and cement was no longer available. The relative value for this particular service remains true today. Repair work on several forts performed with lime and/or hydraulic lime in just the past few years are already failing. More to follow... Mike E ---------- Original Message ----------- From: Brian Robinson <[log in to unmask]> To: [log in to unmask] Sent: Sat, 7 Apr 2007 12:10:45 -0400 Subject: Re: [BP] White wash 2 > Mike, > > I think that your concept of different products being used in different areas of a fort makes sense. Why use a would you use a soft lime mortar in an exterior wall that might be pounded my smooth bore artillery? Maybe, since a softer mortar would be more able to absorb impact. I don't know...?In Fort Pulaski the exterior walls of the fort are made of soft locally made Savannah Grey bricks while the exterior of the gun ports were made of hard red bricks made in Baltimore and Virginia. The use of the hard bricks around the gun ports was because the pressure created during the firing of the gun would have blown apart the softer bricks used in the wall. Inside the fort the gauged brick work in the arches of the casemates are the hard imported brick while many of the structural columns are the softer brick.These materials probably had different mortar since they had to perform different tasks in the structural and combat performance of the structure. > > I am very familar with the creation of traditional lime mortars from chalk, limestone, oyster shell, etc having done some of this myself with my kiln and rick burn. I am however a bit fuzzy on natural cements and the materials that give lime non hydraulic vs. hydraulic qualities. Can you fill me in? I have John Weavers book A Legacy in Brick and Stone which is a great resource for third system fort fans. > > Thanks, > > Brian > > -- To terminate puerile preservation prattling among pals and the uncoffee-ed, or to change your settings, go to: http://listserv.icors.org/archives/bullamanka-pinheads.html ------- End of Original Message ------- -- To terminate puerile preservation prattling among pals and the uncoffee-ed, or to change your settings, go to: <http://listserv.icors.org/archives/bullamanka-pinheads.html>