Chrome Tanned Wet Form?

[Acro]

I've read that wet forming leather is only done with vegetable tanned leather.  Why isn't chrome tanned leather used for wet forming?

I'm new to this and I don't have a full understanding of how it all works.  Your patience is appreciated!

[LatigoAmigo]

This is because chrome tanned leather does not absorb water; it's tendency is to repel water.

[Itch]

A lot of chromed tan leathers will leach out salts that could lead to issues on where it is used ..

[AdamGadut]

Chrome tanned leathers are too soft and pliable, they never retain any shape. Hardly even retains stamp marks. 

[Acro]

Thank you, you three, for the replies!  Super helpful!

Itch, can you elaborate on "could lead to issues on where it is used "?  How so?

Thanks again everyone!

[Itch]

A lot of products we make get installed on motorcycles. If the salts start to leach from the leather and tear up the chrome or finish "rust and corrosion" on a bike that would be a problem. Bridal and Latigo are about all that we use .

[Acro]

Yes, those are issues!

Thanks for the explanation!  :D

[Stetson912]

It's just the way the leathers are tanned. Vegetable tanned leathers get their properties from vegetable tannins. Oak bark is very popular and that's where "oak " and "bark" tanned leather gets its name in some instances. 

Chrome tanned leather uses chromium salts and gets different properties from this. 

Before leather becomes leather, it is simply a shaved degreased animal skin. This skin is primarily made up of a protein Called collagen. In order to make skin into leather and not some disgusting decaying mess, you must eliminate the water in the collagen. The two most popular ways of doing this are by soaking the skin in vegetable tannins and other organic matter which will slowly allow the vegetable tannins to replace the water in the collagen. This takes time, up to two months and several applications and soakings, but you are left with an organically preserved animal skin now known as vegetable tanned leather. 

Chromium tanned leather on the other hand is far "easier". That is to say, it doesn't require skill or time. 90% of leather today is chrome tanned. The skin is acid washed and treated to allow absorption of the chromium sulphate and other chromium salts such as chromium oxide. The chrome tannages agent usually about 33% chromium sulphate to 26% chromium oxide. Its these chromium salts that will replace the water in the collagen. Chromium oxide is not water soluble whereas chromium sulphate is. The whole process can be automated and finished in one day. 

Chromium salts however, are much smaller than the organic vegetable tannins. This causes chrome tanned leathers to be thinner and more supple. 

Chromium salts, especially chromium sulphate, are powerful oxidizers. This means they will oxidize metals pretty easily. So use on holsters or knife sheaths or anything else that will contact metal of any significance is not recommended. 

Because of these different tannages, they offer completely different properties. Veg tan will absorb water, fibers expand, and it becomes more malleable and moldable. When it dries it's shape is retained and sometimes stiffer than it began. 

Chrome tanned is easily hydrophobized (water proofed) and even when it isn't, it contains nearly a third of it's mineral tannins in the form of water insoluble chromium oxide. So it already won't absorb water anywhere close to the degree veg tan will. What little water is taken on won't aid much in molding and shaping. On the other hand, chromium tanned leather has about 5 times the tensile strength than veg tan does. This makes it great for bags and heavy duty applications. 

That's more information than you wanted wasn't it...? 

[Acro]

1 hour ago, Stetson912 said:

That's more information than you wanted wasn't it...? 

Wow . . .

That was the most amazing streamlined shot of information you could give!  I have learned, I have been taught.

I am thankful and appreciative (and impressed) by that . . . thank you for taking the time to write that up.  That info is something that, no doubt, will help others who are learning like me.

I'm floored . . . thank you again! 

Edited September 22, 2017 by Acro

[Stetson912]

You're welcome. Keep learning! If you poke around deep in the archives here you'll find lots of neat stuff.