Here’s a novel approach to preserving the wall everyone wanted to tear down.

The team first examined 15 paint chips and observed that all had a maximum of two or three layers of acrylic paint – brushstrokes as opposed to spray paint. Then, they used Raman spectroscopy to characterise the chips and identified titanium white, azopigments (yellow and red chips) and lead chromate (green) as the primary pigments present.

By mixing common, commercial paint with titanium white the scientists quantified the dye dilution in mixtures used by the artists. They trained a machine learning algorithm to predict the ratio between the pigments using Raman data at various pigment concentrations. From the dataset, they extracted wavenumber values as features while concentration values served as labels. Thus, a custom neural network was built for regression tasks, predicting pigment concentrations. It was discovered that the paint chips contained titanium white and up to 75% pigments, depending on the piece of wall from which it was sourced. The results rivalled those achieved using laboratory equipment.

Apparently the Stasi were lax in recording paint methods.