What can go wrong with steam cleaning leather ?
Steam Cleaning – Leather is made by chemically cross-linking the protein collagen in hides & skins.
This is done in many different ways, using different chemistry and approach. The results from the different tanning systems improve the hydrothermal stability of the tanned collagen matrix so that it will not denature / deteriorate at elevated temperatures and will stand a cycle of drying / re-wetting / drying with no significant bad results.
The degree of hydrothermal stability is determined by the type of tanning system and how strong are the bonds chemically between the tanning agent and the protein molecules of the collagen.
At the low end of stability you get vegetable tanned and oil tanned leather and at the upper end, the mineral tans such as chrome, aluminium and zirconium.
Each tanning agent imparts a significant amount of the final character to the leather that it makes (flexibility / firmness, density, hardness etc).
Chrome tanned leather in the tannery will stand a boiling test without shrinkage – this is one of the production measures used to verify the process is complete and why in footwear, chrome is still the preferred leather to remain flexible after all of the heat treatments that occur during shoe making. Other mineral tans will not produce as high a performance as chrome.
With very heavily finished leather (effectively fully pigmented – plastic coated if you like) it may be possible to get away with a surface steaming, but there’s no guarantees with that since you don’t actually know what’s underneath and it’s chemical constituents…
If you take the approach that wet heat is potentially damaging…… you’ll be about right, its always advised to use water based products made from the finest natural soap flakes, failing that a a slightly damp cloth is better than steam cleaning or using harsh house hold chemicals.
( With thanks to John Avery FSLTC at Avery Leather Consulting Ltd(c) 2016 for his help in producing this document )