# Enhancing 3D-Printed Clay Models for Heritage Restoration Through 3D Scanning
## 3 Results
When compared to previous studies [67], there is a notable contrast in production times. Traditional methods, where the fabrication of plaster molds alone can take several days, combined with the preparation of clay pastes, often extend the total production time of a single piece to over a week [66]. In contrast, the present investigation significantly reduces this timeframe, as similar pieces are printed in just a matter of 6.3-10.9 h. This highlights the efficiency of 3D printing in terms of both time and precision for reproducing complex ceramic objects. Considering the challenges identified in previous studies [68], such as the difficulties associated with removing liquid from formed parts, which is often prone to defects, time-consuming, and energy-intensive, the methodology employed in this research offers improvements. By focusing on less massive elements, the process enhances efficiency, reducing the likelihood of defects and minimizing resource consumption during the drying phase. This advancement not only streamlines production but also contributes to more sustainable practices in the manufacturing of ceramic pieces. The creation of molds for specific pieces leads to higher costs due to the custom nature of the process. However, this method is more efficient for the replacement or installation of repetitive, identical pieces, where multiple reproductions can justify the initial investment in mold-making. Another advantage is the precision and consistency in reproducing ornamental elements. The use of digital twins ensures that the printed pieces are exact replicas of the originals, maintaining proportions and details with a fidelity that is difficult to achieve with manual techniques. This is especially relevant in the restoration of heritage elements, where preserving authenticity and aesthetic integrity is crucial. Moreover, the digital reproduction allows a proper anastylosis, as it could be perfectly possible to print only the missing parts of an element and to achieve an accurate fitting with the existing parts. Additionally, the ability to use clay as the printing material is an advancement, as it allows the restored pieces to integrate seamlessly with the originals without clashing in appearance or materiality. The clay used in printing has physical and aesthetic properties similar to traditional ceramics, facilitating its subsequent firing and surface treatment, thus ensuring visual and structural cohesion within the architectural context. In terms of durability and resistance, the clay-printed pieces demonstrated adequate stability after firing, comparable to that of traditional ceramic pieces. This suggests that 3D printing is not only viable for restoration but can also provide durable and resistant solutions, even in exterior environments where exposure to climatic conditions may be a determining factor. On the other hand, one challenge observed in 3D printing with clay is the visibility of printing traces on the surface of the pieces, an inherent characteristic of the additive manufacturing process (Figure 7). Unlike traditional ceramic restoration techniques, where artisans can achieve smooth surfaces and refined finishes through manual modelling and polishing, 3D printing leaves layer patterns that, although precise, may be visible to the naked eye. However, despite this aesthetic difference, it is important to note that these printing traces do not compromise the integration of the restored pieces within the broader heritage context. According to current restoration codes [34], which prioritize the preservation of authenticity and minimal intervention, the incorporation of these printed pieces is considered appropriate. The visible traces integrate coherently with the architectural ensemble, respecting the visual and material harmony of the original work. Additionally, these traces can be minimized through post-processing techniques such as manual smoothing or the application of slips and glazes, which help reduce their visibility without altering the structural properties of the pieces.