Cross Sections

A cross section of paint from the Royal Albert Bridge


The extent of sampling will depend on the number of individual elements within a room, and the amount of information available. A single room may require between forty and one hundred samples.

This shows the number of samples that were required from the architrave in the Drawing Room at Brodie Castle
This shows the number of samples that were required from the architrave in the Drawing Room at Brodie Castle



The location of each is recorded and carefully numbered. Being small and fragile, the samples are next embedded in a clear polyester resin in order to support them during the polishing process.

The samples are given a unique reference number and then placed in a silicone rubber mould



The resin blocks are then cut in half


Each half is polished with a succession of progressively finer abrasive cloths


The aim is to present a smooth and optically-clear face in order for the full sequence of paint layers to be examined under the microscope.

A cross section being examined under the microscope


The nature of the priming coat will be made clear, and the undercoats can be differentiated from the top, or finish, coats.

Patrick Baty carried out an analysis of the paint on the exteriors at Culzean Castle
A text-book cross section taken from a garden door at Culzean Castle


The same process may also be used to gain an idea of the structural integrity of the paint layers. Their effective adherence to the wall, and inter-coat adhesion can often be gauged by looking at the composition of each layer.
This cross section shows the problem caused by a layer of 'Oil Bound Distemper'; – the overlying paint will flake off