TFL have unveiled SellatanCheck indicator for wet-white tanning which uses glutardialdehyde (GDA) to detect the state of tannage.

The new test method makes tanning with adelhyde tanning agents simple and easy to check. The indicator allows the end point of tanning, that is the diffusion of the tanning agent and its fixation on the hide fibre, to be more easily detected, even on unsplit hides.

After a few drops of Sellatan-Check have been applied to a sample of the hide, the indicator reacts with aldehyde groups to show a stain – the darker the colour, the more free adelhyde is present in the skin.

The colour reaction is evident after five minutes. If the cut edge is not dyed through to the interior, the tanning agent has not penetrated far enough into the skin and tanning must continue. Complete penetration of the tanning agent is indicated by a uniform colouration of the cut edge.

SellatanCheck can also be used to check the fixation of the tanning agent. The indicator reacts with aldehyde groups to generate a colour which reveals the presence (penetration) or the absence (fixation) of glutardialdehyde during the tanning process.

The indicator is said to help avoid subsequent corrections during tanning and reduce the number of rejects during shaving. Storage of wet-white is described as more reliable, avoiding an excess of preserving agents.