What can go wrong with steam cleaning leather?
Steam Cleaning – Leather is made by chemically cross-linking the protein collagen in hides & skins.
It’s all about the chemistry!
This is carried out in many different ways by using different chemistry and approach. Then, the results from the different tanning systems improve the hydro thermal stability of the tanned collagen matrix. This means that it will not denature / deteriorate at higher temperatures. So now we know, it will also withstand a cycle of drying / re-wetting / drying with no bad results.
The degree of hydro thermal stability is determined by the type of tanning system and how strong the chemical bonds are 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. However, at the upper end, you get 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 flexible / firm, dense, hard etc.
Chrome Tanned Leather
Chrome tanned leather in the tannery will withstand a boiling test without being shrunk. So, this is one of the production measures used to make sure the process is complete.
Why in footwear?
Chrome is still the preferred leather to remain flexible after all of the heat treatments that occur during shoe making. This means that, other mineral tans will not produce as high of a performance as chrome does.
Finished leather (pigmented)
Heavily finished leather (effectively fully pigmented – plastic coated if you like) may be possible to get away with a surface steaming. However, there’s no guarantees with that since we don’t actually know the chemical constituents or what’s underneath…
Taking the approach that wet heat is potentially damaging…… you’d be about right. Therefore, it’s always advised to use water-based products made from the finest natural soap flakes. Even a slightly damp cloth is better than steam cleaning or using harsh household chemicals.
( With thanks to John Avery FSLTC at Avery Leather Consulting Ltd(c) 2016 for his help in producing this document )