The Pennsylvania Blue Project An Introduction

Transcription

1 CONTENTS 1 The Pennsylvania Blue Project, An Introduction 2.Merchant s Exchange, A History of the Building and its Alterations 3.The Choragic Monument of Lysicrates 4. The American Vignola 5. Marble Decay: An Overview 6.Condition Recording and Assessment: A Conservator s Guide 7. Conditions Recorded 8. Bibliography 9. Schedule 1

2 The Pennsylvania Blue Project An Introduction Independence National Historical Park (INHP) is home to several of the most significant monumental public buildings of the early American republic. Three of these buildings, the First Bank of the United States ( ), the Second Bank of the United States ( ) and the Merchant s Exchange ( ), span a period when Philadelphia served as the nation s capital, and then as its financial and cultural center. Reflective of this history, these three buildings physically embody and communicate the wealth and promise of the new nation through their developed academic neo-classicism and then unprecedented use of monumental masonry construction with local stone resources. The preservation of these buildings as architectural icons of American federalism and finance was formally recognized with the establishment of Independence National Historical Park in The increasing importance of monumental masonry construction in establishing the various styles and modes of American building began in the early nineteenth century with the revival of Greek classicism. White marble, cut and assembled to evoke the architectural prowess of the ancients, was promoted as the material of choice. The massive and easily accessible beds of Pennsylvania marble, also known as Pennsylvania Blue or Montgomery County marble, quarried just north of the city, was an important regional building stone for public and domestic structures during the first half of the nineteenth century. Benjamin Latrobe's Bank of Pennsylvania ( , demolished c.1870) and William Strickland's Bank of the United States ( ) were among the first monumental stone structures to showcase the area's famous marble. On May 8, 1811, Benjamin Latrobe delivered an anniversary oration before the Society of Artists of the United States in Philadelphia, extolling the importance of the city's precious marble resources: 2

3 The beautiful marble with which this neighborhood abounds, and the excellence of all other building materials, give to Philadelphia great advantages in this branch of the fine arts. The first building in which marble was employed as the principal material of its front, is the Bank of the United States Only one year after its completion the Bank of Pennsylvania was built such a building so different from all that had preceded it in form, arrangement, construction, and character [that] the style of this single building has given to the Philadelphian architecture, even in our plainest brick dwellings, a breadth of effect and response vainly sought in other cities. By the middle of the nineteenth century poor performance of the stone and improved transportation systems that increased the availability of other marbles from Maryland, Massachusetts and Vermont all contributed to the demise of Pennsylvania marble as a building stone. Once a building stone acquires a record of poor weatherability and is no longer commercially viable, there usually is little motivation for continued use of the material. In most cases, it is only years later through renewed conservation studies of deterioration and treatment of historic buildings that information about the properties and performance of specific building materials and technologies is updated or reevaluated. In the case of Pennsylvania marble, its short-lived fame and restricted use have resulted in limited scientific study of its deterioration and responses to conservation treatments. In December 1994, in response to observed stone failure at the Second Bank of the United States, a preliminary assessment of the exterior masonry and characterization and analysis of the stone was initiated by the National Park Service (INHP) and conservator Virginia Naudé. This led to temporary protection and emergency stabilization of critical areas of the entablature for public safety. Historically there has been periodic dimensional loss of the marble through spalling on the columns and along the entablature. Additionally, in unsheltered areas of the ashlar walls, many stones display a deep pattern of loss through contour scaling of the stone faces. 3

4 In 1996 the Architectural Conservation Laboratory (ACL) of the University of Pennsylvania in conjunction with Independence National Historical Park (INHP) began a program of stone characterization and physio-mechanical testing of potential consolidation methods for the Pennsylvania Blue marble. 1 In 1999 following these initial studies, a multi-phased conservation plan was developed and initiated with the Park beginning with the preparation of a detailed CADbased survey of the exterior masonry conditions and the compilation of a history of past repairs and treatments to the building.** Phase 1 of the survey began with the north and west elevations in Also during this period, preservation staff from the Northeast Cultural Resources Center Building Conservation Branch of the National Park Service executed pilot mortar repairs. The exterior masonry conditions survey was brought to completion during Phase 2 of the project, surveying the south and east elevations in Presently, all of the exterior masonry has been carefully inspected and conditions recorded, digitized drawings produced, and preliminary assessments formulated. Data gathered from the exterior masonry survey will be used in preparation for GIS-based diagnostic assessment and remedial and preventive intervention. The National Park Service now has the opportunity to provide the most comprehensive research on Pennsylvania marble and its conservation due to the prominence of these three monumental buildings at Independence National Historical Park. While each building possesses distinct conditions that must be recognized individually, there is much that can be gained by addressing the full range of variations in the use, performance, and weathering of the marble and by comprehensively surveying and cataloguing the conditions across all three buildings. In addition, a wider testing program can be implemented to evaluate treatments, repairs and preventive measures to address existing damage and minimize future marble deterioration and loss, and to predict areas of the stone predisposed to future failure. This program, named The Pennsylvania Blue Project, has the potential of providing much needed information on the history, use, properties, deterioration and treatment of Pennsylvania marble as used in thousands of buildings found throughout the city and surrounding region. 1 Jocelyn Kimmel. Characterization and Consolidation of Pennsylvania blue marble, with a case study of the Second Bank of the United States, Philadelphia, PA (master s thesis, University of Pennsylvania, 1996). 4

5 Merchant s Exchange A History of the Building and its Alterations William D. Brookover ORIGINAL CONSTRUCTION The Philadelphia Merchants' Exchange with its massive classical design in marble underscores the significance of this financial lnstitution in the early history of the nation and the city. The building was built in 1834 to house the newly formed Phfladelphia Exchange Company. From the middle of the 18th century, merchants had met in small coffee houses near the waterfront to conduct business. By the early 19th century. Phfladelphla's merchants had grown to the point of needing a larger home to accommodate their transactions. They commissioned William Strickland, one of the United States' earliest native-born professional architects to design a new building on a triangular lot bounded by Dock, Walnut, and Third Streets. This location was conveniently near the waterfront and the financial district, and presented Strlckland with an elevated, relatively isolated site Webster pp Strickland took full advantage of the architectural possibilities of the site and designed a freestanding monumental structure in the Greek revival style, with the main entrance facing east toward Dock Street. The design combined elements of ancient Greek architecture gleaned from the pages of The Antiquities of Athens, by James Stuart and Nicholas Revett, with early 19thcentury construction techniques and materials. The column capitals are based on Stuart and Revett's plates of the Corinthian order found at the Choragic Monument of Lysicrates in Athens. The portico's eight Corinthian capitals were designed to visually harmonize with those supporting the portico of the nearby First Bank of the United States a short way up Dock Street. Strickland's design for the Exchange was boldly innovative with its placement of one structure. a lanternshaped copy of the same Choragic Monument used for the main order of the bufldng. on top of a three-story semicircular portico. The building presented a memorable sight with its curving colonnade flanked by monumental exterior stairs, topped by the notable lantern [Petrak 1963). During construction 30,811 cubic feet of marble were delivered from Montgomery County for John Struthers and his Italian masons hired to put up the marble facade on the building's thick brick walls, and to carve embellishments at the cornice, the water belt, the portico, and west facade. Samuel Henderson & Son supplied the marble for the exterior from their quarry operating in Upper Merion Township. The Hendersons operated one of the principal quarries in Montgomery County near Phfladelphia. This quarry produced mostly blue marble, but also some pure white. Both varieties were used in the building. The belt of Pennsylvania marble in nearby Montgomery 5

6 County is described as limestone in 19th century geological literature. David Henderson is listed as the marble quarrier on the cornerstone (Simon 1961). The column capitals were carved in Italy of Carrara marble. Strickland sent full size drawings and insisted that the proportions and dimensions be strictly followed (Gilchrist pp ). In 1838 the east portico received marble lions to embellish the staircases at either end. These were copied from Canova's lions sculpted for the tomb of Pope Clement XII at St. Peter's in Rome. They were a gift to the city from John Moss, who commissioned them from Signor Fiorelli, an Italian stone carver working in Philadelphia (Fairmount Park Art Association 1974, p.60). ALTERATIONS 1901 Alterations Until the Civil War the Exchange served its original purpose as a center for commerce as well as a home for the Philadelphia Post Office. As the century waned, the Exchange suffered increasing neglect as commerce moved west away from the Delaware River, as well as decreasing popularity as its Greek Revival architecture fell out of fashion. In 1900 a group of capitalists purchased the building and donated it to the Philadelphia Stock Exchange Company. Louis C. Hickman won the competition to design alterations to the building. His design for the building removed the roof and lantern and much of the original interior. The entrance was shifted to the west side of the building facing Third Street. The work carried out in 1901 consisted of gutting the interior, removing the old roof, and then installing a new roof and tower of a different design and placement. It also included the addition of the round piers and recessed entry on the west entrance, the insertion of a new window configuration for the west facade behind the portico. and the replacement of the outermost marble panels on the east portico with windows (Petrak 1963) Alterations S. W. Hollowell bought the building in 1922 and converted it into a produce market. Drawings in park archives dated document the addition of the metal awning and produce stalls that were constructed around the east and north facades as well as the alteration of the interior spaces for office use. Hollowell inserted windows in place of the recessed marble panels along the third floor of the east portico and cut into the shafts of the fur northernmost columns at the east end to receive iron straps and rods to support the pmduce shed roofs below. Sometime prior to 1947 copper netting was placed over the column capitals on both the east and the west facades. The stairs flanking the east portico were demolished and the lion sculptures located there were removed to the grounds of the Philadelphia Museum of Art. The Museum of Art was under construction at that time, and the lions were placed on platforms flanking monumental exterior steps on the west side of the grounds towards Fairmount Park. 6

7 National Park Service Restoration Charles Oeslanger produced a set of drawings dated April 3, 1950 to document the existing structure. The building was also measured and drawn by the Historic American Buildings Survey (HABS) during the summer of The National Park Service purchased the building in The sheds from the produce market were torn down between May and December of As part of the restoration of the building, the National Park Service cleaned the exterior masonry. Several different cleaning methods were sampled on the building. The first floor columns on the north side of the building were cleaned by recutting in May 1953 and as well as sandblasting in December Both of these methods were determined to be unacceptable. Instead, the entire building was cleaned using a high-pressure water spray aimed at the building for lengthy periods of time (24-36hours), with the work being undertaken by the Day Labor force of Independence National Historical Park. The Weekly Field Reports and Day Labor Daily Logs both document the cleaning process but do not specify the pressure of the water spray. The day laborcarpenters put up the scaffolding, the painters did the cleaning and the masons did the pointing work following the cleaning. A memorandum from August 22, 1963 in the park's correspondence file, describes a program of cleaning and pointing and waterproofing to start that year. No reference has been found in the available files to clarify what was intended as waterproofing, or that the waterproofing was carried out. The cleaning began either along Dock Street, or the north side of the building, then progressed to the east side inside the portico. Next, the outer face of the columns were cleaned, at which time the copper netting was removed. The work moved to Walnut Street or the south side and then final to Third Street or the west side. The whole process started in August 1963 and continued until September 1965 with a few months off each winter (NPS Weekly Field Reports ). A restoration program was developed to return the architectural emphasis of the building to its east or portico end, based largely on photographic evidence. Under a separate construction contract, the east stairs flanking the portico were rebuilt, stone columns damaged where iron straps had been cut into the stone were repaired with epoxy patches, the tar was removed from the portico flooring and replaced with new marble, and the roof with its lantern was restored to the building. The lions were moved back into position on June Management considerations dictated that the west facade retain the 1901 alterations which made it the front entrance (Petrak 1963). Recent Repairs By 1984, the epoxy patches on stone Columns 9, 10, 11, and 12 installed in 1965 had begun to fail. The epoxy had shrunk and pulled away from the stone at the thin tapered sections where the 7

8 patches had been feathered into the arises of the flutes. Because the adhesive strength of the epoxy was greater than that of the stone, a thin section of stone pulled away with the patch. These patches were removed in 1984 and replaced with lime-cement mortar patches, tinted to match the color of the stone. During fieldwork associated with the current program of environmental monitoring. Park Mason Frank Doyle identified a serious crack in a projecting abacus and volute in the southwest corner of the capital of Column 10. In consultation with Conservator Virginia Naude', it was determined that the crack was almost continuous and required immediate repair. A stategy was devised to 11 provide support for the weight of the piece in danger of falling: 2) reattach the cracked segment securely to the stone entablature above: 3) fill the major cracks between the capital and the stone volute: and 4) stabilize and fill the damaged volute. Figure 13 shows the repair in progress. Two stainless steel rods were inserted into holes drilled through the cracked piece up into the entablature. The round hole is visible in the curved face of the abacus just to the right of the mason's hand in the photograph. Three small holes were drilled into the cracks on each side of the capital and the figure illustrates the mason injecting an epoxy resin into the cracks and drilled holes. The resin flowed into the crack and filled the drilled holes, acting as small reinforcing rods. Next, the voids in the volute were filled with masonry patching compound to reestablish the original profiles and forms and to prevent further water penetration through the cracks. ACKNOWLEDGMENTS My sincere thanks to Kathryn Sather for her diligent research work in the park's archives during the summer of

9 Choragic Monument of Lysicrates Choragic monuments defined Pronunciation: [kuraj ik, raj, ko ] (key) [Gr.,=of the choragus, the chorus leader], small decorative structures erected in ancient Greece to commemorate the victory of the leader of a chorus in the competitive choral dances. The best known is that of Lysicrates (c.335 B.C.), still standing in Athens, a graceful circular structure showing one of the early uses of Corinthian columns. "Following Lysicrates Street the tourist will come upon the little garden which surrounds the Choragic Monument of Lysicrates. This is a small marble rotunda dating from the 4th cent. B.C. which served as support for the bronze tripod given as prize to the choragos Lysicrates in B.C. The chorus leaders in ancient Greece were rich citizens who paid for the training of the dance-choruses which performed in dramatic productions. The chorus under Lysicrates' patronage won its victory tripod in the Dionysiac contest. The modern Street of the Tripods follows an ancient street of the same name which finished at the Theatre of Dionysos, and which was bordered with similar choragic monuments displaying other tripods as symbols of victory. The Lysicrates monument owes its preservation to the French Capuchin monks who bought it in 1669, and incorporated it in their monastery. 9

10 The monument is a pseudo-peripteral tholos, (2,80 m. in diameter and 6.50 m. in height). The cella is decorated with what seem to be six half-columns with Corinthian capitals, standing on the round base of three steps. These are really whole pillars, joined by slabs serving as walls for the cella, crowned by friezes decorated with tripods in relief. The colonnade is surmounted by an architrave with three bands, carrying on the upper part the inscription : "Lysicrates, son of Lysitheides, from the dame of Kikynna, choragos". "The Akamantid tribe carried off the victory in the boy's choirs, Theon was the flute-player, Lysiades of Athens the choir-master, Evainetos the archon" ( B.C.). Above this there is a frieze showing Dionysos seated on a rock caressing a panther, in the centre of a group of young satyrs who are Serving him with wine from two bowls. Other satyrs brandishing thyrses, torches and clubs, are castigating two Tyrrhenian pirates, who leap into the sea, already half changed into dolphins. This subject, taken from the Homeric Hymn to Dionysos, was also perhaps the subject of the cantata performed by Lysicrates' chorus. At the peak of the cylindrical-conical roof, made of a single slab of marble decorated with overlapping false tiles and corbels and finished with a cluster of acanthus, stood the tripod won by Lysicrates." A Brief History of Lysicrates Monument Going up the hill, towards the Acropolis you will see the monument of Lysicrates. He was a very wealthy citizen of ancient Athens, who sponsored many theatrical performances in the theater of Dionysus, a common practice by the rich people of that time. In 344 B.C, one of the performances he had sponsored, was awarded the first 10

11 prize and Lysicrates received the honors; in memory of this honor, he financed and built this monument. That, however, was only the beginning of the monument's long story. In 1658, a Capuchin monastery was founded on the site by French monks and in 1669 they proceeded buying the monument from the Turks. Lord Byron resided there as a guest during his second visit to Greece. In 1818, friar Francis planted in its gardens the first tomato plants in Greece. In 1829, the monks gave the structure to a foreign traveler, but it proved to be too heavy for him to take it away. Later, Lord Elgin, after stealing the beautiful marble sculptures from Parthenon, wanted to do the same with Lysicrates monument. Fortunately the monks had wised up by that time and stopped him. 11

12 THE AMERICAN VIGNOLA %rial 644 Edition 3 I THE FIVE ORDERS INTRODUCTION 1. A building is a shelter from rain, sun, and wind; this implies a Roof, and Walls to support it. If the walls entirely enclose the space within, there are Doorways for access, and Windows for light. Roofs and walls, doors and windows are the essential features of buildings. 2. Itoofs may be flat, sloping, or curved. A roof with one slope is called a Lean-To, Fig. 1. When two sloping roofs rest upon parallel walls and lean against each other, they meet in a horizontal Ri&e, Fig. 2, at the top, and form a Gable at each end. Roofs that rise from the same wall in 00PVllOHTED 8" INTLRNATIONIL TEXTBOOK COMPINY. ILL RIGHTS REeLRVKD 12 opposite directions form a Horizontal Valley, Fig. 3, at the wall. If the walls make a projecting angle, the roofs intersect in an inclined line called a Hz2, Fig. 4. If the walls meet in a reentering angle, the inclined line of intersection is called

13 Arcade 10 THE AMERICAN VIGNOLA THE AMERICAN VIGKOLiZ 11 a Valley. Circular walls carry conical, Fig. 5 (a), or domical roofs, Fig. 5 (6). If there is more than one story, the flat roof of the lower story becomes the Floor of the story above. If the roof extends beyond the wall that supports it, the projection is FIG. 4 FIG. 5 (a) FIG. 5(b) called the Eaves, Fig. 6. If the wall also projects, to support the extension of the roof, the projection is called a Coynice, Fig. 7. The principal member of a cornice, which projects like a shelf, is called a Corona, Fig walls are generally made wider just at the bottom, so as to get a better bearing on the ground. This projection is the Base, Fig. 9. A similar projection at the top is called a Ca#, or, if it projects much, a Cornice, as has been said. A low wall is called a Parapet. A short piece of wall about as long as it is thick is called a Post, and if it supports something, a Pedestal, Fig. 10; the part between its Cap and Base is then the Die. A tall post is called a Pier, Fig. 11, if it is square, and a Column if it is round. Caps of piers and columns are called Ca#itaZs, and the part between the Cap and the Base, the Shaff. The flat upper member of a Capital is called the Abacus. 13

14 12 THE AMERICAN VIGNOLA 4. A beam that spans the space between two piers or columns, or between a pier or column and a wall, is called an Architrave, or Epistyle. Above it, between the Architrave and the Cornice, there is generally a little strip of wall called the Frieze. Architrave, Frieze, and Cornice constitute the Eztablature. A series of columns is called a Colonnade, Fig. 12. The spaces between piers or columns are sometimes spanned by Arches, a series of which is called an Arcade, Fig. 13. The space between two walls is sometimes covered by a sort of continuous arch, called a Vault, instead of by a floor or roof, Fig. 14. The under surface of a beam or architrave is called its Soffit, and the same name is used also for the Intrados, or under surface of an arch or vault. The upper surface, or back of an arch, is called the Extrados, and the triangular space of wall above is called a Spandrel. The Wall, the Pier, and the Column, with or without a Pedestal, constitute the chief supporting members; the Frieze and Cornice, FIG. 14 with the roof that rests upon them, 2onstitute the chief part of the load they carry. The Architrave, the Arches, and the Spandrels form part of the load, relatively to what is below them, but are supporting members relatively to what is above them. 5. Besides being valuable as a shelter, a building map be in itself a noble and delightful object, and architects are builders who, by giving a building good proportions and fine details, and by employing beautiful materials, make it valuable on its own account, independently of its uses. Their chief instruments in this work are Drawings, both, of the whole building and, on a larger scale, of the different features that compose it and of their details, which are often drawn full size. These drawings comprise Plans, Sections. 14

15 94211 PLATE I VERSA CONGE THUMB MLDG..,f QUIRKED CYM BEAK SUNK PlLLET 15

16 THE AMERICAN VIGNOLA i3 Elevations, and Perspective Views, Fig. 15. They serve to explain the intention of the architects to their clients and to their workmen. MOULDINGS-PLATE I 6. The simplest decorative details and those that are most universally used in buildings are called Mouldings. unk Elld 010 They are plane or cylindrical surfaces, convex, concave, or of double curvature, qnd they are sometimes plain and sometimes enriched by carving. They are called by varibus 16

17 14 THE AMERICAN VIGNOLA technical names: Greek, Latin, Italian, French, and English. The cross-section of a moulding is called its Profile. A small plane surface is called a Band, Face, or Fascia, Fig. 16, and if very small a Filkt, Raised or Sunk, Fig. 17, Horizontal, Vertical, or Imlined. THE AMERICAN VIGNOLA 15 it is turned upside down. But this leads to confusion. The Cymas vary also, Fig. 28, in the shape and relative size of their concave and convex elements. A small Cyma is called a Cymatium. A small moulding placed above a Band, or any larger moulding, as a decoration, is also called a Cymatium, Fig. 29, whatever its shape. A convex moulding is called an OvoZo, Fig 18, Torus, Fig. 19, or Three-Quarter Moulding, Fig. 20, according to the amount of the curvature of its profile. A small Torus is calied a Bead, Fig. 21, Astragal, or Reed, and an elliptical one, athumb Moulding, Fig. 22. Concave mouldings are, in like manner, called Cavetto, Fig. 23, Scotia, Fig. 24, or Three-Quarkr Hollow, but the term Scotia (darkness) is often used for any hollow moulding. A Cavetto tangent to 9 plane surface is called a Congk, Fig. 25. GymaRecta FIG. 27 (a) FIG. 27 (b) FIG. 27 (c) When a convex and a concave moulding, instead of being tangent, come together at an angle, they constitute a Beak Moulding, Fig. 30. Some architectural features, such as Bases, Caps, and Balusters, consist entirely of mouldings. Others consist mainly of plane surfaces, mouldings being employed to mark the boundary between different features, as between the Architrave and Frieze, or between different members of the same feature, as A moulding with double curvature is called a Cyma, or Wave Moulding. If the tangents to the curve at top and bottom are horizontal, as if the profile were cut from a horizontal wavy line, it is called a Cyma Recta, Fig. 26; if vertical, as if cut from a vertical line, a Cyma Reversa, Fig. 27. The Cyma Recta is sometimes called Cyma Reversa, Fig. 26 (c), whet 17 between the Shaft of a column and its Capital, Fig. 31. In these cases the mouldings, since they occur on the edges of the stone blocks, indicate, while they conceal, the position of the joints of the masonry. Mouldings are often placed also in the internal angle where two plane surfaces meet, as is the case between the Frieze and the Corona of the Cornice,. and under the Abacus of the Capital. When placed upon the external angle formed by two planes, they are, in the Gothic

18 16 THE AMERICAN VIGNOLA Styles, Fig. 32, often cut in, so as to lie down below the surface of both planes; but in the Classical Styles, they pro- ject beyond the plane of one of the surfaces, like a little cornice, as is often seen ill the Abacus of a Capital. THE AMERICAN VIGNOLA 17 Convex.-Ovolo, or Quarter Round; Torus, or Half Round; Thumb Moulding, or Elliptical Torus; Three-Quarter Round; Bead, Astragal, or Reed; Three-Quarter Bead. Cbncnve.-Cavetto, or Quarter Hollow; Cong6; Half Hollow; Scotia; Three-Quarter Hollow. Double Curvature.-Cyma Recta; Cyma Reversa; Cymatium; Beak hloulding. Besides the differences of size and shape already mentioned, and indicated in the table, mouldings of the same name differ in the kind of curve they employ. They may be arcs either of circles, ellipses, parabolas, or hyperbolas, or of any other curve. 7. Styles.-Different systems of construction have prevailed among different races, some employing only the Beam and Column, some also the Arch and Vault. In the choice of mouldings, also, some have adopted one set of forms, some another. The forms employed by the Greeks and Romans constitute what are called the Classical Styles; those used in the Middle Ages, the Byzantine, Romanesque, and Gothic Styles. Some of the Gothic mouldings have special names, such as Boltel, Scroll, etc. At the close of the Middle Ages, about 400 years ago, the Classical styles were revived, as the Medieval styles have been during the last hundred years. Both are now in use. The styles of Egypt, India, and China are employed only occasionally and as a matter of curiosity. 18 Horizontal Mouldings, separating plane surfaces, are called a String Course, Fig. 33. TABLE OF MOULDISGS, PLATE I Plane.-Face, Band, cr Fascia; Beveled, Inclined, or Splay Face; Fillet, vertical, horizontal, or beveled, Raised or Sunk. THE ORDER8 8. In the Classical styles, several varieties of Column and Entablature are used; these are called the Orders. Each order, Fig. 34, comprises a Column with Base, Shaft, and Capital, with or without a Pedestal, with its Base, Die, and Cap, and is crowned by an Entablature, consisting of Architrave, Frieze, and Cornice. The Entablature is generally about onefourth as high as the Column, and the Pedestal one-third. more or less

19 18 THE AMERICAN VIGNOLA THE AMERICAN VIGNOLA 19 The principal member of the Cornice is the Corona, Fig. 35. Above the Corona, the Cornice is regularly terminated by a member originally designed to serve as a gutter to receive the water running down the roof. It generally consists of a large Cyma :ornice \ twe3e Archif rave Capital Shaft Basa cap Recta, though the Ovolo and the Cavetto are often used. It is called the Cymatium, in spite of its large size, and whatever its shape. NOTE. - The word Cymatium thus has three meanings: (1) Asmall Cyma; (2) a small crowning member, of whatever shape, though it is most frequently a Cyma Reversa; (3) the upper member of a Cornice, occupying the place of a gutter, whatever its shape, though it is generally a large Cyma Recta. In Classical Architecture, the Cyma Recta seldom occurs, except at the top of the Cornice and at the bottom of the Pedestal. It would seem as if a cornice that occurs at the top of a wall and carries the edge of a roof would properly have a Cymatium, this being ;!e place for a gutter, and that Cornices used as String Courses, half way up a wall, would the Corona, is often added. At the top of the Architrave is a projecting moulding that, when square, is called a Tmia, and the face of the Architrave is often broken up into twc or three Bands or Fascias, Fig. 38. FIG. 36 The Abacus of the Capital also has a sort of bed mould beneath it, which, when convex, is called an Eckinus, Fig. 39, from the sea shell, Fig. 40, which it resembles in shape. FIG. 37 The little Frieze below it is called the Necking. But if the bed mould under the Abacus is concave, it dies into the necking like a large CongC, and the two together constitute the Die Basa Taenia naturally be without this member. But the significance of the Cymatium has frequently been overlooked, in ancient times and in modern. Many Greek temples have a Cymatium on the sloping lines of the gable, where a gutter would be useless, Fig. 120, and none along the Eaves, and in many modern buildings the cornices are crowned by large Cymatia in places where there are no roofs behind them. 19 The Corona is supported by a Moulding or group of Mouldings, called the Bed Mould. A row of brackets, termed Blocks, Fig. 36, Modillions, or Mutules, Fig. 37, according to their.shape, resting on the Bed Mould and supporting the soffit of Bell of the Capital, Fig. 41. The Abacus is square in plan, but the Echinus, or the Bell below it, is round, like the column. At the top of the shaft is a member called the Astragal. :onsisting of a Bead, Fillet, and CongC. It has a flat surface

20 20 THE AMERICAN VIGNOLA., THE AMERICAN VIGNOLA 21 on top, as wide as the projection of the CongC, Fig. 42. At the bottom of the shaft is another Cong6, below which is a broad fillet called the Cincture, Fig. 43. The Base generally FIG. 39 FIG. 40 has, below the base mouldings, a plain member called the Plinth, which is square in plan like the Abacus. - The Shaft diminishes as it rises, Fig. 44, the upper diameter being only five-sixths of the lower, and the outline is not straight, but curved. This a \g curve, which is called the Edasis, or bending, as of a bow, generally begins one-third of the way up, the lower third being! cylindrical. The Entasis is not FIG. 41 to be confounded with the Diminution, which is generally one-sixth, the upper diameter being five-sixths of the lower. 20 Generally, the Pedestal also has a Corona and Bed Mould, but no gutter, above the Die, and a Base Moulding and Plinth below it. 9. In the choice and use of mouldings, the tastes and - fasnions of the Greeks and Romans were quite contrary to those of their successors in the Middle Ages. The Ancients preferred to use vertical and horizontal surfaces at right angles to each other, and seldom used an oblique line, or an acute or obtuse angle, as the Gothic architects did. They also preferred the Cyma Reversa, seldom enploying the Cyma Recta, which in the Middle Ages was rather the favorite. Moreover, as has been said, the Gothic architects, in decorating a corner or edge, often cut it away to get a moulding, but the Ancients raised the moulding above the plane of the surface to which it was applied. In the composition and sequence of mouldings also, the Classical architects generally avoided repetition, alternating large and small, plain and curved, convex and concave. The convex and concave profiles seldom describe an arc of more than 180 degrees, and except in the case of the Beak Moulding and of the Bead, mouldings are always separated by Fillets. When a moulding is enriched, it is generally by carving ornamental forms, Fig. 45, upon it that resemble its own profile. The Greeks frequently employed elliptical and hyperbolic profiles, while the Romans generally used arcs of circles. Among the Greeks, the forms, Fig. 46, used by the Doric race, which inhabited Greece itself and had colonies in Sicily and Italy, were much unlike those of the Ionic race, which inhabited the western coast of Asia Minor, and whose art was greatly influenced by that of Assyria and Persia. The Romans modified the Ionic and Doric styles, Fig. 47, and also devised a third, which was much more elaborate than either of them, and employed brackets, called M~diZZions, in the Cornice. This they called the Corinthian, Fig. 48. They used also a simpler Doric called the Tuscan, Fig. 49, and a cross between the Corinthian and Ionic called the Composite. Fig. 50. These are the Five Orders. The ancient examples

21 22 THE AMERICAN VIGNOLA THE AMERICAN VIGNOLA 23 vary much among themselves and differ in different places, and in modern times still further varieties are found in Italy, Spain, France, Gemany, and England. Temple of Concord at Rome The best known and most admired forms for the Orders are those worked out by Giacomo Barozzi da Vignola, in the 16th century, from the study of ancient examples. The Orders that are shown in the large plates almost exactly follow Vignola's rules. 21

22 Tuscan FIG THE AMERICAN VIGNC)LA 22 Doric Ionic FIG. 47 Corinthian FIG 48

23 26 THE AMERICAN VIGNOLA 23 Composite FIG. 50

24 24

25 Marble decay: an overview In developing a conservation program for any masonry building, a variety of factors must be considered including the age and type of the building, the expected performance of the stone, the chemical composition and mechanical properties of the stone, the nature of the decay mechanisms, and the rate of deterioration of the stone relative to its building location and environment. Marble is a carbonate-based metamorphic rock which like most building stones, will undergo alteration and decay from a wide range of factors including pollution and freeze-thaw, salt, and thermal cycling. The mineralogical composition and grain structure of each type of marble will ultimately determine how vulnerable it is to decay from weathering. While all marbles are susceptible to chemical dissolution from acidic agents, the texture and fabric of the rock will dictate to a large degree its specific response to weathering. Degree of foliation, presence of secondary minerals such as micas, graphite and pyrite, and grain size and shape will all affect its durability. Mechanical damage, often indicated by cracking, will result by overloading the cohesive grain-to-grain strength of the marble. The original stone of the Second Bank is of two varieties: a coarsely crystalline creamy white marble and a light blue banded or mottled marble. Both are interbedded with dark blue to black siliceous dolomite. The marble is weakly metamorphosed and contains abundant micaceous inclusions and the calcite is not strongly recrystallized. The marble is loosely textured, with a marked foliation (or planar) fabric forming a series of parallel planes that are weakly held together. The dominant mineral is light blue calcite grains ranging in size from microns, angular to sub-rounded in shape and nearly of pure calcium carbonate. There are also small amounts of magnesium and iron. 1 1 Elaine S. McGee. Marble Characteristics and Deterioration. In Philadelphia Merchants Exchange Conservation Strategy. Environmental and Cultural Resources Research Monograph No. 1 (Washington, D.C.: National Park Service, 1992),

26 Mechanical damage can occur in several ways. Columns and other supports can crack by tensile, compression or shear forces while smaller architectural elements can fail from traffic or construction vibrations. Long-term stresses cause plastic deformation or creep. More dramatic damage can occur from blasting or seismic shock. Quarry blasting is often used to extract rock for construction. The explosion triggers a stress pulse that the rock can absorb and store. As the pulse pressure lessens, the internal stresses are released by stone fragmentation and microcracking. The resultant cracking and spalling provide moisture and salt entry causing greater damage. Salt crystallization is considered potentially one of the most damaging mechanisms to stone buildings, especially when a building is in a climate prone to wet-dry cycles. Salt crystallization begins when salts are dissolved in water and are transported through the pores of the stone. Salts can also be deposited on the surface from the atmosphere, evaporating groundwater, or contaminants such as bird guano, cleaning treatments, and deicing salts. Precipitated surface salts, or efflorescence, cause less damage than those crystallizing within the pores of the stone. Such subflorescence can exert sufficient internal disruptive pressure to overcome the grain-to-grain cohesive strength of the stone matrix. The amount of damage depends on many factors: most notably the species and combination of salts, the microclimate, and the porosimetry of the stone. Moreover, the presence of salts promote condensation and rising damp which escalates the entire process. Most marbles are fairly dense with porosities of one percent or less; however as the grains become detached from internal mechanical stresses, porosity can increase and thereby escalate deterioration. Acidic attack from dry and wet deposition or from inappropriate acidic cleaning will dissolve the calcite and dolomite matrix and from gypsum crusts. Secondary mineral inclusions such as pyrite can accelerate this decay by producing sulfuric acid, which can also convert the calcite to gypsum. The formation of gypsum 26

27 distorts surface details and is more vulnerable to loss as it is 25 times more soluble than calcite and its expansive structure is weakly attached to the unaltered stone substrate. The presence of expansive clay secondary minerals can also swell and produce mechanical stresses in the stone when wet or erode away more easily than other less water-sensitive inclusions. Carbon dioxide in rainwater forms carbonic acid, which over time converts soluble calcium carbonate to soluble calcium bicarbonate. The weathering of crystalline marble is a complex interaction of several decay mechanisms and varies according to the particular structure and composition of the marble as well as its orientation in the building. The surface of the Pennsylvania Blue marble is vulnerable to surface weathering because its calcite structure is weakly metamorphosed with poorly interlocking grain boundaries, and it has a large percentage of inclusions. Dimensional expansion-contraction and chemical dissolution of the calcite grains starts the release of locked-in stresses by the anomalous temperature behavior of calcite, and by the expansive action of trapped moisture. Dilation occurs, resulting in the crumbling and cracking of the column arises and detail edges. Sugaring and micro pitting are the first indications of surface erosion and dissolution. Wet marble exhibits lower strength and hardness and dry climate conditions trigger evaporation that transports soluble calcite to the stone surface and leads to case hardening. Freeze-thaw cycling exacerbates loss of the casehardened surface and causes flaking and delamination, especially where the foliation of the marble is parallel or oblique to the surface. Thermal cycling and its associated mechanical cracking are most prevalent on the columns and especially on the column fluting. In summary, cracking and grain loss occurs when internal stresses from metamorphosis are released during quarrying, stone working, diurnal and seasonal thermal expansion, or by moisture expansion. Cracking occurs at grain boundaries and boundaries between the calcite and weaker secondary minerals. 27

28 Thermal expansion of calcite is not uniform. When heated, the calcite crystal expands along the long axis but contracts along the short axis. Spalling is triggered by the same mechanisms as cracking, but the internal stresses are relieved when parts of the stone detach in concentric spalls. Severe spalling on the rear face of the columns of both porticos suggests other factors may also be at play. The presence of heavy black gypsum crusts in these areas, attributable to the lack of rain water washing, may be exacerbating detachment by the crystallization of gypsum in the microcracks. The specific deterioration of both types of Pennsylvania Blue marble at the Second Bank must be studied in greater detail to establish a hierarchy of decay mechanisms affecting the building overall or in specific locations based on stone type, orientation, environment and microclimate, and previous treatment. 28

29 Condition recording and assessment: a conservators guide The idea of a procedurally rigorous survey of field conditions, including the integration of various forms of information (e.g., construction and maintenance records, existing photographs, environmental data, etc.) and various methods of recording, for the purposes of diagnostic assessment of a building including its fabric and systems, has been an important step in developing both accurate and holistic approaches to building and site conservation. Such field surveys force the building conservator to account for every possible etiological relationship between material, construction, design, environment, use, and maintenance, through the detailed recording of conditions in the present and over time. By recording condition in conjunction with other physical aspects of a structure or site during the initial phases of documentation, and by considering what such conditions mean throughout a project, the condition survey becomes a powerful diagnostic tool for answering a range of research questions ultimately concerned with design, performance, alteration, treatment, and maintenance. Through the development of clearly defined, causal-free terminology based on a descriptive recording of observed symptoms, the condition survey can at once document the type, extent, location, pattern, severity (degree) and status (active/inactive) of observable phenomena. Past conditions may also be recorded using historical images and detailed descriptions when available. In so doing, and in conjunction with other data sets (such as compositional analysis, use and maintenance history), condition recording assists in the explanation of decay mechanisms, as well as providing diachronic evidence for the construction, use, and repair or neglect of the building and site. A symptomatic recording of conditions means to describe what one sees at time present according to physical appearance. A condition survey usually occurs at one brief moment in the life of the structure or site, yet a structured approach to the evidence visible and invisible allows a temporal reading of what was, is, 29

30 and will or might be. Causal explanation can then follow based on a reading of site evidence along with associated environmental and structural monitoring, material analysis, historical research, etc. Even without archival images of past conditions, a detailed survey of current conditions can trace the physical progression of weathering through relative time by way of shifting patterns, extent, severity, or even type transformation of decay such as disaggregation into scaling or flaking and eventually loss. Since immediate and ultimate causes may be open to several interpretations, it is imperative that the survey be as accurate and free from assumptions as possible. However it is also important to realize that the act of interpretation begins the moment the recording process occurs, if only by its selecting of conditions chosen for observation. Conditions are the incidental residual result of events and processes. Conditions, like stratigraphic deposits, are a by-product of many factors: use, aging, neglect, repair the whole array of human and natural factors. If conditions are recorded as evidence, a more accurate account of cause/effect relationships can be established and appropriate interventions conducted. The built environment, like its natural geological counterpart, is a collection of unique outcomes at once constantly changing through differential weathering, yet similar in the predictability of the natural entropic and anthropic processes responsible for the change. This obvious yet important observation reinforces the role condition surveys can play in identifying the unique combination of factors responsible for material change. Despite the fundamental information condition surveys provide on the type and extent of material damage and the diagnosis of material and building failure, there exists a general lack of coordinated recording standards in architectural conservation. To this end, a detailed, illustrated condition glossary was developed for the marble of the Second Bank. 30

31 DIAGNOSIS - The conclusion reached by detailed analysis. (Greek-to discern, literally to perceive apart) ETIOLOGY - The study of causes, origins, reasons. The cause of a disorder as determined by diagnosis EVIDENCE The data on which a judgment or conclusion may be based, or by which proof or probability may be established, present and plainly visible, clear, obvious (Latin-evidens-to see completely) PHENOMENA An observable event or occurrence that is directly perceptible by the senses. (from the Greek-to appear or show). SYMPTOM Any circumstance or phenomenon regarded as an indication or characteristic of a condition or event; a departure from normal appearance. 31

32 Conditions Recorded The glossary of conditions developed during Phase One of the Second Bank survey will be used as a basis for recording conditions for the Merchant s Exchange. After careful study in the field during the seconf phase of the Second Bank survey several major and minor modifications were made to some condition definitions from the original survey glossary. The following table indicates those conditions whose definitions were moderately changed: Definitions Condition Orientation of Foliation Planes addition of "faceoriented" stones Moderate Cracks less than 1/8" 1/16-1/8" Deteriorated mortar present mortar present Mortar Joint in joints is friable but eroded back 1/2" or more in depth Dimensional Loss 4"sq., 1" deep 2" sq., 1/2" deep Stone Redressing did not exist added Surface Unique did not exist added It is of utmost importance to notice two major changes concerning the definitions of differential (surface) erosion and contour scaling. These conditions occur frequently on all facades of the Second Bank and so play a significant role in the building s deterioration patterns. While their specific definitions can be read in the glossary, the most important difference between the 1999 and 2003 definitions is that what was recorded as surface erosion in 1999 was identified as flaking in It was also determined that the description used to describe surface erosion in 1999 is better characterized as differential erosion. The second major change to the conditions glossary was the re-working of the definition of contour scaling. The Phase Two team ascertained that contour scaling is, in essence, flaking to a greater extent and so modified the definition to reflect this change. 32

33 Aside from the definitions, the classifications of the conditions were also changed. Phase Two conditions were grouped according to whether they were subtractive or additive. All other conditions were categorized as other. Colors used were based on and represent these groupings. The 2003 glossary was also updated with new photographs taken by team members in the field. 33

34 Masonry Conditions Glossary 34

35 35

36 36

37 37

38 38

39 c c 39

40 a) b) a) b) b) 40

41 41

42 42

43 43

44 44

45 45

46 46

47 47

48 48

49 49

50 50

51 51

52 52

53 53

54 54

55 mortar a 55

56 56

57 57

58 58

59 59

60 60

61 61

62 62

63 63

64 64