*3.2. Properties of the Surfaces after Process Tests*

Visual inspection of the coatings after the three months process trial and their comparison with the control surfaces showed that all coatings prepared by magnetron sputtering (T1, T2, T3, U1 and U2) were physically present, although some color changes were apparent (Figure 6). The TiO2 sol coating (MC) appeared to be still present after the process test at Brewery C but was at least partially removed at the other two breweries. It was noticeable that many of the surfaces were heavily soiled, particularly those that had been on trial at Breweries A and B.

**Figure 6.** Images of coupons after the three month brewery trial. See Table 2 for sample descriptions.
