Restoration research discovered and defined original plaster as well as its adjustments. Arch motive terminates cut-outs of triangular lunettes. South side cut-out situated closer to the western wall was cancelled by installing compressed barrel vault and a staircase in 18th century. The only preserved part is a top tip with a ribbed ornament. Original plastering created during the 5th construction phase is light brown to brown-grey colour and contains small lumps of lime. The primary adjustment of the vault is cream coloured. Apparently, the vault was coated in full by white-lime colour broken up into ochre. Colour paint is smooth and firm and well linked to the undercoat. The plaster is probably applied by using a float giving it a smooth and firm surface. It is a double-layered lime plaster. In the first plastering phase a nuclear plaster was created including the raising of ribs. In the second phase a thin layer of stuccoed plaster made of air-slaked lime and sand was applied. The surface was smoothed by applying milk of lime. We can also see several secondary adjustments on the plaster that were performed during various construction phases.