KIMIKA Volume 27, Number 1, pp. 29-40 (2016) © 2016 Kapisanang Kimika ng Pilipinas All rights reserved. Printed in the . ISSN 0115-2130 (Print); 2508-0911 (Online) https://doi.org/10.26534/kimika.v27i1.29-40

Chemical Characterization of Historical Brickwork of the Church Convento in Pagsanjan,

Jan-Michael C. Cayme1*, Aniano N. Asor1, Jr., Maveen Kim Alexis T. Alano2 and Eric T. Miranda2

1 Chemistry Department, College of Science, De La Salle University, 2401 Taft Avenue, Malate, 2 School of Chemical Engineering and Chemistry, Mapua Institute of Technology, Intramuros, Manila

This study reports the chemical composition of historical brickworks from Franciscan- built church complexes in the Philippines. An old brick sample from the Spanish colonial period church convento at Pagsanjan, Laguna was characterized by atomic absorption spectroscopy (AAS), infrared spectroscopy (IR), thermogravimetric analysis (TGA), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX). Conventional hot plate aqua regia (1:3 HNO3:HCl, v/v) digestion method was employed to extract iron, calcium, and magnesium from the brick sample. The combined AAS and EDX results yielded a percentage composition of iron ranging from 5.48 to 6.62%, calcium ranging from 1.50 to 3.72%, while magnesium ranges from 0.083 to 0.12%, respectively. These amounts were compared to a similar AAS and EDX study made on a historical brick sample from Ilocos Norte. The presence of possible pores on the brick’s microstructure was confirmed by SEM. Minerals consisting of hematite, kaolinite, illite, quartz, and calcite were present in the sample, as well as trace amounts of other minerals based on IR peak intensities. Upon heating to about 800⁰C using TGA, the loss of bound water from the sample’s internal surface structure and the decomposition of brick minerals and carbonates are evident.

Keywords: clay brick; atomic absorption spectroscopy; infrared spectroscopy; scanning electron microscopy with energy-dispersive X-ray spectroscopy; thermogravimetric analysis; cultural heritage conservation

INTRODUCTION served as the Order’s base of operations in a particular area. The complex is generally The Franciscan Order of Friars Minor or composed of the main church structure, the OFM was the second religious order that bell tower, the convento or the parish priest’s arrived in the Philippines in 1578 during the residence and the cemetery. Most of these early years of the Spanish conquest of the Franciscan-built structures still exist and have country. They were given the task of handling retained the old building materials which date the spiritual administration of the whole back to the Spanish colonial period. In province of Laguna where Pagsanjan is general, the Franciscan architectural style is located (Alarcon, 1998). Part of this work is described as having a humble simplicity, the construction of church complexes which subdued and modest, which reflects the ideals

* Author to whom correspondence should be addressed; email: [email protected] 30 Jan-Michael C. Cayme, Aniano N. Asor, Jr., Maveen Kim Alexis T. Alano and Eric T. Miranda and teachings of their founder, St. Francis de spacious main sala (receiving room), kitchen Assisi (Klassen, 2010). area and the comedor (dining room). Other places for clinics, classrooms, storage spaces The Pagsanjan church complex, also known as (bodegas) and some pens for domesticated the Parish of Our Lady of Guadalupe, was animals are found on the ground floor (Jose, built in 1688 from light construction materials 1992; Mata, 2005). At present, the convento has made of bamboo and nipa under the been adapted for more modern use, supervision of the Franciscan missionary, Fray containing a mixture of old and new Agustin de la Magdalena. It was later replaced construction materials, with elements of its with a bigger and more permanent church original structure still apparent. structure made of adobe in 1690. This adobe structure was burned during the British This study describes the chemical composition occupation of the Philippines from 1762 to of a brick sample used as construction 1764 and was subsequently rebuilt. From material on the outer front wall of the about 1850’s to 1870’s, a major renovation Pagsanjan church convento. The result will serve was initiated by the Franciscan Fray Joaquin as a baseline data of historical brick chemical de Coria by building a belfry and adding a composition that is very important in huge dome on the church structure. This restoration works and in the production of renovated structure suffered heavy damages replacement bricks compatible with the during an American aerial bombing of Laguna original material. Sampling of brick material in World War 2. It was eventually was performed to ensure that very minimal reconstructed following its original pre-war amount of sample were taken from the architectural design and the structure remains collection site which is adequate to up to this day (Zaide, 1975). accomplish the various instrumental techniques described in this study. The The Franciscan archival records on the church Pagsanjan church and adjoining convento are convento’s construction history are very scarce. not in the Philippine National Museum’s The convento is a two storey structure made of registry of National Cultural Treasures and adobe stones and clay bricks. These are National Cultural Churches. common construction materials in Spanish-era Laguna Province. The brick materials used for The three important minor elements (iron, construction are presumed to be calcium and magnesium) which determine the manufactured in the latter part of the 1800’s brick’s overall strength and durability were during the major church renovation done by quantified using atomic absorption Fray de Coria. These were evident from pre- spectroscopy (AAS) techniques. This was war archival photos, brick layering style and supported by the total elemental composition technique, and the physical characteristics of data obtained from the scanning electron bricks found on the outer walls (Figure 1). microscopy with energy-dispersive x-ray spectroscopy (SEM-EDX) technique. The The convento’s plan is rectangular in shaped general clay mineral composition was with a cloister enclosing an open space (Figure provided by infrared spectroscopy (IR) while 2), which in the olden days functions as an the quality of the brick sample in terms of its inner courtyard or a garden (Alarcon, 1998). manufacturing process was shown using One side of the convento forms the walls of the thermogravimetric analysis (TGA) and church and the back portion is connected to a scanning electron microscopy (SEM) capilla (small chapel). From the convento, the techniques. church can be accessed through the ground floor. The Franciscans originally built the EXPERIMENTAL convento following a design adapted from traditional Philippine architecture which was Collection of brick sample. The historical characterized by open and airy spaces. The brick sample was acquired in December 2012 second floor houses the parish residence, a from an irregular-shaped loose brick fragment

KIMIKA • Volume 27, Number 1, January 2016 Chemical Characterization of Historical Brickwork of the Church Convento in Pagsanjan… 31

Figure 2: General floor plan of the Pagsanjan church complex and the sampling site. The brick fragment used in this study where a representative sample amount was obtained.

then decant. The supernatant liquid was diluted to the mark with distilled water in a 100 mL volumetric flask (Cayme and Asor, Jr., 2015).

Sample digestion for extracting calcium. Conventional aqua regia digestion was performed on three sample replicates consisting of about 0.5000 g powdered brick sample in separate 250 mL glass beakers and covered with watch glass. Each sample replicate was digested separately for 3 hours on a hotplate in 40 mL3:1 mixture of HCl and

Figure 1: Location of Pagsanjan, Laguna and the old HNO3 (aqua regia) at 110⁰C. Once the mixture brick wall of the Pagsanjan church convento. evaporates to near dryness, each replicate was diluted with 20 mL of 2% HNO3 (v/v with (about 5 cm x 5 cm x 4.5 cm) approximately 3 H2O) and centrifuged. The supernatant was feet from the base of the front wall portion of subsequently transferred into a 100 mL the church convento (Figure 2). The brick volumetric flask and diluted to the mark with fragment has a light reddish-brown outer distilled water (Cayme and Asor, Jr., 2015). surface and light red interior. From this fragment, 12.4g of brick sample was obtained Analysis by Atomic Absorption Spectroscopy (AAS). A series of standard at an approximate depth of 1-2 cm from the solutions were prepared from commercially surface. The remaining brick fragment was available 1000 ppm iron, magnesium and returned afterwards. calcium, AAS standard concentrates (Fluka brand, analytical standard grade) in separate 50 Sample digestion for extracting iron and mL volumetric flasks and diluted to the mark magnesium. Prior to digestion, three with distilled water. A chemical suppressant, replicate powdered brick samples with a mass 2.5 mL of 5% w/v Sr(NO3)2was added to of about 0.5000 g each were soaked for 24 each standard solution and brick sample for hours in 50 mL, 3:1 mixture of HCl and determining the calcium and magnesium HNO3 (aqua regia) at room temperature. After contents. The calibration curves were this soaking period, each sample was further prepared using the following concentration digested with another fresh mixture of 40 mL ranges: from 2 ppm to 10 ppm for iron, 0.3 aqua regia solution for 3 hours on a hotplate at ppm to 2 ppm for magnesium and 0.1 ppm to 110⁰C. Upon evaporation to almost dryness, 2ppm for calcium. The blank solution used each replicate sample was diluted with 20 mL throughout the experiment was distilled water. of 2% HNO3 (v/v with H2O), centrifuged and The digested brick samples were prepared

KIMIKA • Volume 27, Number 1, January 2016 32 Jan-Michael C. Cayme, Aniano N. Asor, Jr., Maveen Kim Alexis T. Alano and Eric T. Miranda separately by diluting 2 mL aliquot for iron, 15 heating rate of 10⁰C/minute. The percentage mL aliquot for magnesium, and 1 mL aliquot by weight of the sample relative to the change for calcium, respectively. Each sample aliquot in temperature was recorded. was diluted to the mark with distilled water in individual 100 mL volumetric flasks. The RESULTS AND DISCUSSION absorbance was measured in a Shimadzu AA- 6300 Atomic Absorption Spectrophotometer Amount of Iron, Calcium and Magnesium with an air-acetylene gas mixture and hallow- by Atomic Absorption Spectroscopy cathode lamps as radiation source. All (AAS). Historical bricks or ladrillos are mainly measurements were done in triplicates. The made of clay mixed with sand and water. This wavelength for detection was adjusted to mixture is then moulded, dried for days and 248.3 nm for determining iron, 422.7 nm for locally fired in a horno or brick kiln (Navarro, calcium and 285.2 nm for magnesium, 2007). The brick materials are usually sourced respectively. and manufactured in situ, thus, creating products that have different chemical Analysis by Scanning Electron compositions across every province in the Microscopy with Energy-dispersive X-ray Philippines (Fernandes et al, 2010). Spectroscopy (SEM-EDX). SEM observations in the back-scattered electron Clays are composed of silicates and aluminates mode were recorded using the SEM/EDX with varying amounts of metallic elements like JEOL JSM-5310 scanning microscope iron, calcium and magnesium. These elements combined with Oxford Link Isis in the spot- serve as fluxes which facilitate the fusion of profile mode, to characterize the mineral particles at lower temperature and microstructure of the brick material. The influence the brick’s overall quality and observations were performed by dispersing a stability. The characteristic red color of bricks small amount of dry, powdered brick sample is also attributed to the amount of iron and on doubled sided conductive adhesive tape the firing temperature (Torraca, 2009). attached on an aluminium stub and coated Knowing the amount of these elements in a with gold. The EDX elemental profile was brick sample is crucial in manufacturing also obtained from the SEM sample region compatible materials for restoration works. taken at 62eV system resolution to determine The AAS data shows that among these three the elemental composition. elements, the percentage of iron is higher in the sample with 5.870%, followed by calcium Analysis by Infrared Spectroscopy (IR). with 3.328% and magnesium with 0.0893%, The infrared spectrum was recorded using a respectively (Table 1). These quantities were Thermo Scientific Nicolet 6700 FT-IR computed based on the following calibration standard curve equations; for iron: Spectrophotometer in the mid frequency y=0.041115x + 0.028921 (r=0.9982), for region (4000- 400 cm-1). A mixture of KBr calcium: y=0.047340x + 0.0012269 powder and a small amount of powdered (r=0.9995), and for magnesium: y = 0.85056x brick sample was grounded together and then + 0.41618 (r=0.9947). The results are within a pressed to form a transparent, thin pellet. The 95% confidence limit and the standard sample was initially heated in an oven for 3 deviations signify that these values were hours at 105⁰C to ensure a completely dried clustered around the mean. sample. A similar AAS study was reported for a brick Analysis by Thermogravimetric Analyzer sample collected from Ilocos Norte (Cayme (TGA). Thermal transformations of the brick and Azor, Jr., 2015). It showed a percentage sample were characterized using a Mettler composition of iron in the range of 4.193 to Toledo TGA. A starting mass of 6.400mg 4.418%, calcium from 0.123 to 0.203%, and brick sample was heated from a temperature magnesium from 2.346 to 2.458%, range of 25 to 800⁰C, under dynamic air and respectively. Figure 3 is a graph comparing the

KIMIKA • Volume 27, Number 1, January 2016 Chemical Characterization of Historical Brickwork of the Church Convento in Pagsanjan… 33

Table 1: Summary of AAS Data for Iron, Calcium and Magnesium Content.

Mass of brick Average Mean Element Sample Code sample (g) (% composition) (Std. Deviation) Fe-01 0.5062 6.379% 5.870 ±1.14* Fe Fe-02 0.5009 5.749 % (0.460) Fe-03 0.5035 5.483 % Ca-01 0.5014 3.719 % 3.328 ± 0.864* Ca Ca-02 0.5030 3.052 % (0.348) Ca-03 0.5009 3.212 % Mg-01 0.5062 0.094 % 0.089± 0.0149* Mg Mg-02 0.5009 0.083 % (0.006) Mg-03 0.5035 0.091 % * at 95% confident interval

iron from AAS (5.870%) with that of the EDX Ilocos Norte 5.870% (6.62%) is about 13%, which is quite small. This Laguna 4.418% indicates that iron is distributed homogeneously

3.328% within the brick sample matrix. Moreover, the 2.458% difference in the amount of calcium and magnesium between the two instrumental methods averages from greater than 50% for 0.089% 0.203% calcium, and about 20% for magnesium. Since Fe Mg Ca these elements are lighter compared to iron and

Figure 3: Comparison of the amount of iron, are more water soluble (Torraca, 2009), it is magnesium and calcium from Laguna and Ilocos possible that its distribution from the brick Norte using AAS. sample may not be uniform. chemical components from these two A comparison of a similar EDX study made different locations. The brick sample from on a historic brick sample obtained from Laguna was made with clay or inorganic raw Ilocos Norte (Cayme, 2016) shows that there materials rich in iron and calcium, while the are variations in the chemical compositions sample from Ilocos Norte has higher depending on its location. This can be magnesium content. These different values definitely influence the overall consistency of Table 2: Elemental Percentage Composition the brick products. of the Brick Sample from EDX

Total Elemental Composition using Element Atomic % Energy-Dispersive X-Ray Spectroscopy O 43.65 (EDX). Table 2 shows that silicon, aluminium C 32.41 and iron are the major inorganic elements in the Si 9.00 sample which is consistent with the clay and Fe 6.62 sand origin of historical bricks. A similar Al 5.91 decreasing trend on the amount of iron (6.62%) Ca 1.50 followed by calcium (1.50%) and lastly by Ti 0.44 magnesium (0.12%) was also observed in EDX K 0.28 (Table 2). Magnesium was present in trace Mn 0.07* amounts. These values show good agreement Mg 0.12* with the amount obtained from AAS. The Total 100.00 difference between the percentage amounts of *trace amounts

KIMIKA • Volume 27, Number 1, January 2016 34 Jan-Michael C. Cayme, Aniano N. Asor, Jr., Maveen Kim Alexis T. Alano and Eric T. Miranda rationalized by looking at the geological 48.19% Ilocos Norte features of these places. Pagsanjan Laguna is 43.65% in close proximity with dormant volcanoes 32.41% Laguna (Mt. Makiling and Mt. Banahaw), a volcanic 29.42% complex (Maculod), and the , 10.17% 6.62% 6.41% which is a volcanic-tectonic formation by 9.00% caldera eruptions and extension tectonics. 3.18% 5.91% Most notable is the presence of collapse structure bounding Laguna de Bay that O C Fe Si Al suggests a probable relic of a larger ancient Figure 5: Comparison of the distribution of elements caldera system (Adams, 1910). On the other in the brick sample from Laguna and Ilocos Norte hand, Ilocos Norte, which is on the western using EDX (for elements >2.00% composition) slope of the central Cordillera mountain range, is generally composed of shale, to the Ilocos Norte sample is typical of basalts interbedded sandstone, and conglomerate type of minerals. These mineral types are with minor carbonate or tuffaceous mostly calc-alkaline, evolving to high components (Eslava-Faustino et al., 2013). potassium calc-alkaline for intermediate and These surrounding features greatly influence evolved lavas. The Laguna de Bay lavas, in the elemental composition of the raw turn, are bimodally calc-alkaline and high materials in making bricks. potassium calc-alkaline (Soucek et al., 1989). The presence of magnesium (0.12%) confirms The sample from Laguna has a higher the occurrence of ferromagnetic rocks in the percentage of iron compared to aluminates, surrounding area of Pagsanjan. Low amounts while for the Ilocos Norte brick sample, of the mineral rutile from rocks found in aluminates are more abundant than iron Laguna are evident from the element titanium (Figure 5). The greater percentage of iron (0.44%). Trace amounts of manganese were (6.62%) is attributed to ferromagnetic rocks attributed to subduction-related rocks which is which are abundant in the Laguna area also common in the Laguna area (Sudo et al., compared to Ilocos Norte. Higher amounts of 2000). The soil from Laguna is not a good silicates (9.00%) and oxygen (43.65%) element source of sodium and copper since the from the Laguna sample are due to the amount of these elements are very presence of volcanic rocks which is common insignificant compared to the brick sample in the area and mainly in the form of SiO2. from Ilocos Norte. The occurrences of High percentage of silicon and oxygen different elemental composition in two elements confirms that silicic types of rocks historic brick material supports the idea that are present as aggregates in the sample different source of raw materials for brick (Schumann, 1993). These volcanic rocks making yields different properties. Hence a comprising the Macolod volcanic field have a wide range of composition from basalt to 1.50% rhyolite type of minerals. Basalts occur only in Ilocos Norte 0.57% small monogenetic centers in the Macolod 1.11% Laguna Corridor, while dacites and rhyolites appears 0.12% to be present only in the Laguna de Bay area 0.44% and Mt. Makiling (Smith, 1913). These 0.22% 0.28% 0.25% 0.27% minerals are rich in SiO2 which is consistent 0.21% 0.07% 0.00% 0.00% with the EDX data. 0.00% Ca Ti K Mn Mg Na Cu For elements having percentage composition less than 2.00% (Figure 6), higher percentage Figure 6: Comparison of the distribution of elements of calcium (1.50%) and potassium (0.28%) in the brick sample from Laguna and Ilocos Norte obtained from the Laguna sample compared using EDX (for elements <2.00% composition)

KIMIKA • Volume 27, Number 1, January 2016 Chemical Characterization of Historical Brickwork of the Church Convento in Pagsanjan… 35

A B

Figure 7: SEM image of the brick sample showing a magnification of (a) x1,500, and (b) x5,000. The arrow points to the possible pores on the bricks microstructure. blanket approach of conserving historical modes for Si-O and Al-O, and the metal-OH bricks is not recommended. It is not unusual bending modes are seen from 600 to 950 cm-1 that Pagsanjan or Laguna province in general, (Schroeder, 2002). Since the sample was may have manufactured their own bricks heated at 105⁰C for 3 hours to drive out the because it is a highly progressive town during water molecules prior to the IR analysis, the the Spanish colonial period (Zaide, 1975). spectrum indicated a very weak band centered at 3475 cm-1 and 1618 cm-1 which are assigned Brick Microstructure using Scanning to the remaining water molecules absorbed by Electron Microscopy (SEM). The physical the brick structure. Strong absorption bands microstructure of the brick sample was were also observed for the fingerprint region analysed based on the SEM image on Figure from 400 to 1500 cm-1 which is important in 7. As shown in both magnifications (x1,500 inorganic mineral analysis (Derrick et al., and x5,000), the presence of pores are evident. 1999). This region was compared with major Different pore sizes of approximately 10μm mineral constituents of clay and sand which (Figure 7A) and 2.5μm (Figure 7B), are hematite, kaolinite, illite, quartz and calcite respectively are observed, which might as shown in Figure 8. The IR spectrum for eventually lead to the weakening of the these mineral standards was obtained online mechanical behaviour of the brick sample from the Mineral Spectroscopy Server of the (Torraca, 2009). Evidence of weak regions in California Institute of Technology (Kelly, the brick microstructure is seen from the lack 2016). Their samples were done in KBr of crystal stacking in both SEM images. pellets, baseline corrected and analysed using Perkin Elmer FTIR Spectrometer. Mineralogical Composition using Infrared Spectroscopy (IR). For an IR spectrum in Table 3 lists the absorption of these minerals general, the range from 3400 to 3750 cm-1 is in the IR fingerprint region compared with the assigned to OH stretching modes common in brick sample and its assignments. It shows clay minerals; the absorbance from 700 to that the characteristic mineral peaks are also 1200 cm-1 is usually assigned to stretching present in the brick sample confirming its clay

KIMIKA • Volume 27, Number 1, January 2016 36 Jan-Michael C. Cayme, Aniano N. Asor, Jr., Maveen Kim Alexis T. Alano and Eric T. Miranda

this absorption was observed for the hematite Brick Sample and attributed to impurities in the natural sample. Quartz, which is mainly composed of SiO2 (Schumann, 1993), absorbed strongly at this wavenumber.

% Transmittance % For pure calcite, which is mainly CaCO3, the 1650 1450 1250 1050 850 650 450 important bands for C-O are the out-of-plane Wavenumber (cm-1) bending (ʋ2) at 874 cm-1, asymmetric

stretching (ʋ3) at 1420 cm-1and the in-plane bending (ʋ4) at 712 cm-1(Sathya et al., 2012). Only the weak bands at 858cm-1 (ʋ2) and 769cm-1 (ʋ4) was observed from the brick sample (Figure 8).

The strong absorbance between 450-500 cm-1 in the brick sample is assigned to Fe-O bending and Si-O-Si bending (Saikia et al., 2010). From Figure 8, hematite absorbs % Transmittance % strongly at this region due to the presence of high concentrations of iron. The characteristic red color of bricks is attributed to this mineral. Illite also contains iron which 1650 1450 1250 1050 850 650 450 explains its absorbance in this region. Wavenumber (cm-1) Kaolinite, illite and quartz absorbs strongly at this region due to the presence of silicon (Si- Hematite Kaolinite Illite O-Si bending) in their crystal structure. Some Quartz Calcite absorption peaks in the brick sample was not fully resolved which signifies the presence of -1 Figure 8: IR fingerprint region (450-1650 cm ) of the other mineral groups. This is expected since brick sample together with reference spectra from sand and clay are composed of different common inorganic minerals found in clay and sand. minerals. and sand origins. The fingerprint region of the Thermal Analysis of Brick Sample using brick sample has a broad peak approximately Thermogravimetric Analyser (TGA): -1 between 1000-1300 cm (Figure 8) which is Figure 9 shows that around 750⁰C, a visible assigned to Si-O stretching (Petrenas et al., decomposition of minerals in the brick sample 2012). It is also present as broad peaks in the was observed. Initially, there is partial mineral kaolinite, illite and quartz. This is oxidation of the sample in the ambient air at expected since these minerals contain silicon. around 70⁰C which resulted to a slight Hematite, which is mainly composed of iron increase in weight. As the temperature and oxygen, has a weak absorption band increase from 80 to 100⁰C, the weight lost is -1 within this Si-O region (1084cm ). Like most attributed to the evaporation of water. It was mineral compounds, hematite is rarely found followed by a constant loss of weight between in pure composition (Schumann, 1993). 100 to 740⁰C which might be due to the Calcite which is mainly composed of CaCO3 combustion of organic matter and the further doesn’t absorb at this region. The sharp peak removal of trapped water inside the brick -1 at 796 cm on the brick sample is also microstructure (Cardiano et al., 2004). The assigned to a Si-O stretching (Petrenas et al., decomposition process culminates by a drop 2012). This is again present in the minerals in weight detected between 750 to 800⁰C kaolinite, illite and quartz. A weak band for (Figure 10) which is due to the

KIMIKA • Volume 27, Number 1, January 2016 Chemical Characterization of Historical Brickwork of the Church Convento in Pagsanjan… 37

Table 3: Comparison of IR Peaks for the Major Mineral Components of Brick Raw Materials with the Sample.

Wavenumber (cm-1) Assignments Quartz Calcite Hematite Illite Kaolinite Brick Sample 454 --- 464 470 464 459 Si-O-Si bending Fe-O bending 506 --- 544 532 530 495 for hematite; Si- O-Al stretching Si-O for quartz; 692 ------694 636-684 671 Si-O-Si bending (ʋ4) C-O in plane bending 774 712 780 776 746 769 for calcite; Si-O stretching Si-O stretching; 792 --- 798 798 792 796 OH deformation linked to Al, Mg (ʋ2) C-O out-of- --- 874 ------858 plane bending for calcite OH deformation ------910 908 --- linked to Al 1078 --- 1084 1030 1002-1032 1070 Si-O stretching ------1112 1128 Si-O stretching (ʋ3) C-O asymmetric --- 1420 ------bending for calcite

101 0.00020

100 0.00015 99 0.00010

98 (1/s) 97 0.00005

%Weight 96 0.00000 95 -0.00005 94

93 -0.00010 20 120 220 320 420 520 620 720 Temperature

Weight(%) First Derivative

Figure 9: Thermogravimetric analysis of the brick sample

KIMIKA • Volume 27, Number 1, January 2016 38 Jan-Michael C. Cayme, Aniano N. Asor, Jr., Maveen Kim Alexis T. Alano and Eric T. Miranda

94.2 0.00000

94.1 -0.00001 94.0 -0.00001 93.9

-0.00002 (1/s) 93.8 -0.00002 Axis Axis Title 93.7 -0.00003 93.6

93.5 -0.00003

93.4 -0.00004 720 730 740 750 760 770 780 790 800 Axis Title

Weight (%) First Derivative

Figure 10: Thermogravimetric analysis for temperature greater than 720⁰C dehydroxylation of illite and chlorites (Sutcu, difference was correlated with the geological 2014) as well as possible decomposition of characteristics of the two provinces and calcite. Bricks are generally fired at a supported by AAS and EDX data. As temperature ranging from 800 to 1,000⁰C in a expected, the brick sample originated from horno (Navarro, 2007). Degradation was clay and sand due to the observed IR observed below this firing temperature which absorption peaks attributed to the minerals: signifies the presence of non-ceramic hematite, calcite, illite, kaolinite, and quartz. materials which may be due to organic Bricks are also found to be porous as compounds in the brick sample. observed from the SEM data which may be a good indication of its physical characteristics. CONCLUSIONS The decomposition of minerals and carbonates in the brick sample below the This study is the first in a series of chemical firing temperature was analysed from TGA characterizations of historical brick materials data. This may imply the presence of organic made under the guidance of the Franciscan compounds that may have contaminated the friars. Further study is needed if there are sample through time. unique brick making methods employed by the different religious orders in the ACKNOWLEDGMENT Philippines. The importance of obtaining the brick raw materials for conservation work The authors would like to express their within the same vicinity of the old structure sincere gratitude to the Municipality of was highly emphasized. This will ensure that Pagsanjan, Laguna, Pagsanjan Tourism, the brick product is more compatible in terms Culture and Arts Development Office, and of its chemical and physical properties with most especially to Rev. Fr. Noel Artillaga, the original material. Different distributions of parish priest of Our Lady of Guadalupe for iron, magnesium and calcium, which are the old brick sample used in this study. The important fluxing agents in manufacturing generous support of the Chemistry bricks, were observed upon comparison Department of the De La Salle University, between the samples from the Pagsanjan Manila, is highly appreciated. This study is not church convento with another brick sample possible without the helpful insights and from an old church in Ilocos Norte. This assistance of the following persons from the

KIMIKA • Volume 27, Number 1, January 2016 Chemical Characterization of Historical Brickwork of the Church Convento in Pagsanjan… 39

De La Salle University, Manila: Dr. Glenn Eslava-Faustino DV, Dimalanta CB, Yumul, Alea, Mr. Michael Ajero, Mr. Irving Chiong, Jr GP, Servando N, Cruz NA. Geohazards, Dr. Maria Carmen Tan, Mr. Mamerto Quizon tropical cyclones and disaster risk and Mr. Reynaldo Coria for the SEM-EDX management in the Philippines: Adaptation in data. The authors would also like to thank the a changing climate regime. J Environ Sci invaluable assistance of Ms. Jessica Balingit Manag. 2013; 16(1):84-97. from the Mapua Institute of Technology for running the TGA. Fernandes F, Lourenco P, Castro F. Ancient clay bricks: Manufacture and properties. In: DEDICATION Bostenaru Dan M, Poikryl R, Torok A. Materials, technologies and practice in historic To the Franciscan friars for building heritage structures. Netherlands: Springer; impressive church structures that forms part 2010. p. 29-48. of our built cultural heritage and are worth protecting. Jose RT. Simbahan: Church art in colonial Philippines 1565-1898. Ayala Foundation Inc.; REFERENCES 1992

Adams GI. Geologic reconnaissance of south Kelly, J. Minerals in KBr pellets [internet]. western . Philipp J Sci. 1910; 5:57-113. Pasadena, California USA: Mineral Spectroscopy Server of the California Institute Alarcon N. Philippine architecture during the of Technology; 2011 [updated 2016 January pre-Spanish and Spanish periods. UST 18; cited 2016 June 28]. Available from: Publishing House; 1998. http://minerals.gps.caltech.edu/files/Infrared _MIR/Minerals_From_JK/Index.htm Cardiano P, Ioppolo S, De Stefano, Pettignano A, Serge S, Piraino P. Study and Klassen W. Architecture in the Philippines: characterization of the ancient bricks of Filipino building in a cross-cultural context monastery of “San Filippo di Fragala” in (revised edition). University of San Carlos Frazzano (Sicily). Anal Chim Acta. 2004; Press, Cebu City; 2010. 519:103-111. Mata RLS. The conservation of heritage Cayme JM. Chemical characterization of conventos. Pintacasi, A Journal of the Cultural historic brickworks made during the Spanish Heritage of the Church in the Philippines, colonial period in the Philippines using 2005; 1:43-46. scanning electron microscopy and energy- dispersive X-ray spectroscopy (SEM-EDX) Navarro M, editor. Common brick and infrared spectroscopy (IR). 31st Philippine manufacture. 1st revised ed. Taguig City Chemistry Congress; 2016 April 13-15; Iloilo Metro Manila: Department of Science and City. Technology, Industrial Technology Development Institute; 2007 June. Cayme JM, Asor A, Jr. Extraction methods for quantifying iron, calcium and magnesium Petrenas T, Kiuberis J, Opuchovic O, Tautkus in a historic brickwork produced during the S, Kareiva A. A closer look at the ancient Spanish colonial period in the Philippines. bricks of historical monuments: essential step Kimika 2015; 26(1):28-38. for the conservation of pottery. Chemija, 2012; 23(3): 194-202. Derrick MR, Stulik D, Landry JM. Infrared spectroscopy in conservation science: Scientific tools for conservation. The Getty Conservation Institute, Los Angeles; 1999.

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Saikia BJ, Parthasarathy G. Fourier transform Soucek J, Holub FV, Jellnek E, Klapov AH. infrared spectroscopic characterization of Calc-alkaline rocks. Encylcopedia of Earth koalinite from Assam and Meghalaya, North Science. Springer US; 1989. Eastern India. J. Mod. Phys., 2010; (1):206- 210. Sudo M, Listanco EL, Ishikawa N, Tagami T, Kamata H, Tatsumi Y. K-Ar dating of Sathya P, Velraj G, Meyvel S. Fourier volcanic rocks from Macolod Corridor transform infrared spectroscopic study of Southwestern Luzon, Philippines: Toward ancient brick samples from Salavankuppam Understanding of the Quaternary Volcanism Region, Tamilnadu, India. Adv Appl Sci Res. and Tectonics. J. Geol. Soc. Phil. 2000; 55:89- 2012; 3(2):776-779. 104.

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