The chimney pieces of Maastricht City Hall.

The Maastricht town hall was decorated by artists with themes linked to the administration of the city and the city hall as a symbol of power. In the Mayor's Room (Edmond Plumier, 1714), Prince's Room (Theodore van der Schuer, 1704) and the Board Room (van der Schuer, 1705), we see the double jurisdiction depicted on the so-called chimney pieces, as the Prince-Bishop of Liège and the Duke of Brabant were Maastricht's sovereigns.

In two Aldermen's Rooms, we find depictions of The Chaste Susanna (by Plumier, 1720) and an allegory of the Arts and Sciences (by Van der Schuer, 1691). Each of these five monumental paintings has undergone previous conservation efforts, including lining, cleaning, and sometimes extensive overpainting. Structurally, the paintings are stable.

However, multiple layers of varnish on each painting have yellowed over time, though they remain transparent. This discoloration has disrupted the balance of colors, shadows, and tonalities: cool colors have warmed, light colors have darkened, and dark colors have lightened. As a result, there is a loss of subtle contrasts and details in the compositions, with an exaggerated contrast between light and dark areas.

Some overpaintings are clearly visible as they have turned white due to the presence of zinc white. This affects the appreciation of the paintings' composition and quality. Older retouches are obscured by the varnish layer, and varnish removal tests indicate that while some retouches dissolve easily, many do not. Additionally, preliminary examinations revealed severe damage to the paint surfaces in both the Mayor's Room and Alderman's Room. Dark areas, in particular, were polished down to the primer during previous conservation campaigns and were then roughly overpainted. Given the size and complexity of the damage, the process of varnish removal, selective removal or thinning of overpaintings, and the filling and retouching of gaps requires significant expertise and specialized knowledge.