One product that has a unique application is Kentmere VC Select Gloss. This paper is used for testing steel castings for flaws by steelworks and laboratories for non-destructive testing (NDT) work. While there are other methods, the most fail-safe method that we know of is the Sulphur Printing process.

The product previously used was Kenthene Satin Grade 4, which is no longer manufactured. The replacement product used by global players in the steel industry, is Kentmere VC Select Gloss.

This can be supplied in cut sheets but for the sulphur printing process it is usually supplied in rolls of 1270mm width x 30 metres.

The full technical detail behind this unique process is as follows:

The process involves immersing a silver bromide paper in 3% sulphuric acid for approximately three minutes.

The sulphuric acid is absorbed in the gelatine layer, the paper is then removed from the acid bath, to drain in order to remove the excess acid and then placed on a machined steel sample surface.

The paper is rubbed smooth to remove air bubbles and to ensure intimate contact between paper and steel. A latent image is then produced on the paper through the following reaction: