This study reports the chemical composition of historical brickworks from Franciscanbuilt 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.

Spanish Colonial Period brick samples dating to the 19th century from the Municipalities of Liliw and Pagsanjan in Laguna, Philippines was investigated. These samples were obtained from two church structures, a church bell tower from Liliw and a church convent from Pagsanjan. Combined X-ray diffraction (XRD), energy dispersive X-ray fluorescence (EDXRF) and Fourier transform infrared (FTIR) spectroscopy allowed the determination of chemical elements and minerals attributed to clay and sand, such as montmorillonite, quartz, corundum, hematite and calcite. On the basis of these compositions, the possible kilning conditions employed to fire the bricks during manufacture was also proposed. MATLAB™ programme was utilised in this study to interpret the data from XRD and FTIR to rationalise the overlapping peaks in the spectrum. Results show that both brick samples were made of clay material that is non-calcareous with low refractory. The firing was performed in an oxidising atmosphere or an open-air environment at an estimated temperature of between 650°C and 850°C. This preliminary study provides a baseline chemical characterisation data of colonial period bricks in the Philippines which will be useful for future conservation and restoration work not only locally but also within the Southeast Asian region.

The lack of information about the correct ways of restoring historical masonry materials from cultural heritage structures tends to create more damage to the said structures. According to Cesare Brandi's theory of restoration, existing historical materials must be replaced with their equivalent. This paper presents the chemical composition of historical mortars acquired from church ruins of barangay Budiao, Daraga, Albay, Philippines. The historical mortar sample was characterized using petrographic analysis, sieve analysis, atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), and infrared spectroscopy (IR). Petrographic analysis shows that the mortar sample is bounded by 90% organic material particularly coral and is held together by microcrystalline calcite (micrite) matrix that comprises of 10% of the total sample mortar composition. Sieve analysis shows a well-graded particle distribution. Atomic absorption spectroscopy (AAS) was also utilized to determine the %Ca for each sieve fraction using HCl for acid digestion. TGA thermograph shows the non-linear drop in weight between 740 o C and 850 o C, which corresponds to the degradation temperature of calcium carbonate or limestone. IR analysis shows essential characteristic peaks of CaCO 3 at 712 cm -1 , 874 cm -1 , and 1437 cm -1 .

The Cagsawa Ruins is a crucial structure of the old church standing 38 km from Mt. Mayon in the province of Bicol. The ruins has been the result of the eruption of Mt. Mayon last February 1, 1814. The remains have become a part of the province's rich history and culture declaring it as one of the national treasures of the Philippines. Preservation is implemented to maintain the part that has remained from centuries ago. But apparently, the material used for preserving this important structure lacks compatibility with the original materials incorporated in the structure. Portland cement has been an alternative for lime mortars through which, in nature, are synthetic and are known to be the source of premature deterioration of soft, historic bricks. This cultural heritage is of importance to the history and must be preserved to its rightful material. By means of petrographic and thermal analysis it was proved that the aggregate from the mortar gathered from Cagsawa came from minerals and marine organisms that the decomposition of the elements confirmed that there are organic compounds present.