Citation: Lara Calderón, M.L.; del Pino, I.; López-Andrés, S.; Sanz-Arauz, D. Characterization and Analysis of the Mortars of the Church of San Francisco of Quito (Ecuador). Heritage 2023, 6, 7495–7507. https:// doi.org/10.3390/heritage6120393 Academic Editor: João Pedro Veiga Received: 8 September 2023 Revised: 26 November 2023 Accepted: 27 November 2023 Published: 29 November 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). heritage Article Characterization and Analysis of the Mortars of the Church of San Francisco of Quito (Ecuador) M. Lenin Lara Calderón 1,2, * , Inés del Pino 3 , Sol López-Andrés 4 and David Sanz-Arauz 1 1 Department of Construction and Architectural Technology, Polytechnic University of Madrid, 28040 Madrid, Spain; david.sanz.arauz@upm.es 2 Faculty of Arts, Design and Architecture, UIDE International University of Ecuador, Simón Bolívar Av., Jorge Fernández Av., Quito 170411, Ecuador 3 Faculty of Arts, Design and Architecture, Pontifical Catholic University of Ecuador, Quito 170121, Ecuador; idelpinom@puce.edu.ec 4 Department of Mineralogy and Petrology, Complutense University of Madrid, 28040 Madrid, Spain; antares@ucm.es * Correspondence: lenin.lara.calderon@alumnos.upm.es or mlara@uide.edu.ec; Tel.: +593-994384851 Abstract: The relevance of the Franciscan community is reflected in the San Francisco church in Quito, which was built between 1535 and 1755. This architectural work belonging to the Franciscan complex was implanted on a plot of land with an area of 3.5 hectares and was one of the first buildings in the Audience of Quito. Eleven mortar samples that covered the walls of the central nave and side chapels were taken from the church’s main temple. The procedure proposed by the authors is based on a combined methodology following the standards and protocols for the less-invasive extraction of heritage samples. Tests included X-ray diffraction, petrography, and scanning electron microscopy with a microanalysis of the samples. Mortars with a rustic composition and rough manufacturing were identified to differentiate two types of mortar, one of earthen with volcanic aggregates and another of lime with volcanic aggregates. The mining data validated the existing historical documentation, the imaginary process, and the stages of the established constructions. Keywords: lime mortar; earth mortar; mortars with volcanic aggregate; mineralogy of historic mortars; Quito; cultural heritage; church of San Francisco of Quito 1. Introduction Quito and its historic center have two areas of heritage protection. One, called the first- order area, is 54 hectares, and the second, called the protection area, is 376 hectares. In this area, there are 4674 built properties [1,2]. The 1888 Quito map, drawn by Gualberto Pérez, shows 17 religious buildings in the first-order area, giving it a conventual character [3]. Years later, in 1978, the city was distinguished as a World Heritage site by UNESCO (Figure 1). The arguments for this award centered around the unity of architecture and the landscape and the human diversity that was concentrated in this urban space [4]. After the Spanish city was founded, the first religious communities to arrive in Quito were Franciscans, Mercedarians, Augustinians, and Dominicans. Each group was assigned and delimited a site in the parish of El Sagrario during the sixteenth century. The Franciscan site is directly related to the cultural pre-existence of the pre-Hispanic market that occupied the first-order area of the historic center. The San Francisco square, the Plaza Mayor square, and the Santo Domingo square were apparently the vertices of the ancient market, located in a complex topography, with two deep ravines and three hills that enclosed the pre- Hispanic site [5]. In this space of symbolic pre-existence, the Spanish city was founded in 1534. The Franciscans settled in Quito in January 1535. By mid-1538, the Franciscans were in possession of the current property, which occupies a full block and is bordered on the Heritage 2023, 6, 7495–7507. https://doi.org/10.3390/heritage6120393 https://www.mdpi.com/journal/heritage