*3.7. Stain Resistance*

Figure 4 presents a graph illustrating the stain resistance behavior of ENS-15 according to a scale of the difficulty degree in removing the stains after the cleaning procedures described in the standard [28]. In this scale, Number 5 represents the easiest stain removal, and Number 1 represents the harder stain removal. In fact, a stain at Number 1 is one that remains even after all the cleaning procedures.

**Figure 4.** Stain resistance behavior of ENS-15 after 24 h covered with the staining agents.

ENS-15 showed high stain resistance for agents such as wine and coffee, which were cleaned only with hot water. Olive oil and ketchup stains were easily removed by detergent, and, after cleaning with an abrasive paste, the green agent (Cr2O3) stain was also removed. For cleaning the other stains left by red (Fe2O3), mustard, and iodine, the specimens were submerged in acidic solution for 24 h. ENS-15 did not show iodine stain resistance because this stain remained at Number 1, as shown in Figure 4.

Peixoto et al. [15,22] also developed an artificial stone with the incorporation of glass waste, but with another type of glass from the industrial lamination stage. They evaluated its stain resistance with the same method and same staining agents, but no stain remained after the test.

Borsellino et al. [34] also evaluated the stain resistance of their artificial marbles developed with marble and epoxy resin and also with polyester resin. However, they used different staining agents and another method. It was pointed out by the authors that plates with more epoxy resin content suffered fewer surface alterations after the stain resistance test, which was attributed to the higher epoxy resin stain resistance.

Stain resistance is kindred to surface pores because, after polishing the stone surface, the internal pores become surface pores, also known as open pores, which hinder the removal of stains [22].

The stain resistance test is important to evaluate the quality of engineered stones because of its application, which takes aesthetics into account, and because of its use in kitchens, bathrooms, and laboratory countertops, which constantly expose ENS to staining substances.
