## 1 Introduction  
Printed products are ubiquitous in our lives. They are used daily, from documents, banknotes, books, and newspapers to packaging. Printing is a special case of surface modification used to obtain a high-quality print that meets visual, functional, and durability requirements. Figure 1 shows the printing process's schematic workflow, from design to post-press. Printing a final product, such as packaging, requires a few technological operations. Before printing, the product is designed, and then a proof of the print is prepared [1]. Before the final printing, proofs are printed, allowing the customer to see how the final printed product will appear. A proof is a perfect sample of the print, which is later sent to a print run [2]. Proofing allows us to verify and confirm the print quality before the actual production. At the same time, it ensures that the graphic design looks as expected and that the colors, shapes, and other graphical elements are accurately reflected on the material on which the final print will be made [3]. There are two fundamental processes of proofing: soft and hard proofing. Soft proofing is a digital process in which a graphic designer or DTP operator (desktop publishing operator), which is a skilled professional responsible for preparing and formatting text, images, and graphics into a final layout suitable for printing or digital publishing [2], uses a calibrated screen monitor to view the design of the print. To achieve the highest quality of soft proofing, the process should be conducted according to ISO standards [4]. Hard proofing involves proof in the form of a physical print on certified white paper with one of three types of finishes: gloss, semi-matte, or matte [5,6]. A hard copy is printed using dedicated proofing machines called proofers and dedicated control software. Neither soft nor hard proofs show an accurate print, especially when the final print is made on a transparent or colorful (not white) base. Furthermore, hard proofing is associated with using raw materials (inks and printing bases) and energy, and at the end of this process, proof prints are utilized. The final print may differ significantly from the client's requirements and, despite prior proof acceptance, can require design changes, which are associated with production costs and the utilization of failed prints. Therefore, a solution to this problem might be the preparation of proofs on production or target substrates. LCA is the most widely used among various tools to determine and quantify a process's environmental impact [7, 8, 9]. LCA allows the evaluation of a product's potential environmental impacts from cradle-to-gate (or cradle-to-grave) [10]. In other words, the LCA methodology allows us to analyze the impact from the first production stage, starting from raw material, to production, to the recycling and final disposal of the product [11]. This methodology is applied to quantify the direct and indirect environmental burdens related to service or production [12]. The LCA methodology is based on international standards, such as ISO 14040 and ISO 14044 [13,14]. According to standard 14040, LCA refers to environmental aspects and potential impacts throughout a products life (i.e., cradle-to-grave) from raw material acquisition through production, use, and disposal [14]. A LCA is performed in four steps [13]: (i) goal and scope defining; (ii) analysis of the set of inputs and outputs; (iii) life cycle impact assessment; (iv) interpretation. LCA is a tool that considers the energy use, consumed resources, emissions, and waste generation of a product or process. The influence of printing products on the environment is not a new topic in scientific research. However, researchers have primarily focused on analyzing the LCA of various  
Figure 1: Flow diagram of the printing process: from design to post-press. types of packaging or waste management.