Leather Watch Strap Restoration

[w30bob]

Hi Gang,

Looks like a very informative forum......I'm hoping to learn a lot. My current project is a leather watch strap from the early 1900's. My problem is it's hard as a rock. I mean so hard that if I try to bend it I'm sure it will snap and break off. I collect early American watches from the turn of the century and keep running into original leather straps that have dried out and were never taken care of. They're usually intact and would be perfectly wearable if the leather wasn't as hard as cardboard. I've done the usual, checked out other leather care sites for tips and tried most of them. I'm talking coconut oil, alchohol, vaseline, heat, etc. I've had the watchstrap sitting in a bottle of linnseed oil for the past 2 weeks, took it out this morning, and don't see much of a change. I mean I can bend it a little, but wouldn't go much further for fear of it cracking and breaking. I'm thinking next I'll oil the leather up real good and put it in a book press I have, maybe forcing the oil into the leather. But I'm just pulling that one out of my butt for lack of other smarter ideas. Normally when the leather is pliable I can remove the strap from the watch, but in this case it's so hard I can't slide the leather enough (at all) to clear the rivet that holds each side of the strap to the watch.

It seems the leather has lost any ability to absorb anything, and I understand there may be a point at which leather can't be saved, so I'm ready to hear that if that's the case as well. So any info you could share about how to soften REALLY hard, very thin leather would be greatly appreciated. Even if this one can't be saved I have others in various states of hardness and maybe the tips you provide might work on some of those. I'll attach a few pics so you can see what I'm talking about. The shininess is from the residual Linnseed oil, as normally the leather is just a flat dull brown. Thanks in advance!

regards,
bob

[Roger Koh]

We need to know that the suppleness of the leather depends on fat and oil.

In a modern tannery, fatliquor is used.

These fat liquors are ionic negative (-ve) charged fat and oil that hydrogen bond with the protein leather fiber.

Water is an example of how hydrogen bonding takes place, being temperature sensitive, it changes to ice below 0C and to steam above 100C.

Similarly, leather is pH sensitive and denatures into stiff rawhide when comes into contact with an alkaline solution, and in the case of a watch strap the sweat when ferments shift and weaken the leather ionic positive (+ve) attraction, the fat and oil breaks the hydrogen bonds and leach out, the leather fiber lose the fat and collapse becomes stick together and the oil that lubricates these millions of interconnecting hinges fail to slide over one another and get stuck.

Besides since fat and oil are VOC volatile organic compounds it evaporates in the presence of heat.

That is how this leather watch strap becomes as you described "My problem is it's hard as a rock. I mean so hard that if I try to bend it I'm sure it will snap and break off. ".

Now, how we put the fat and oil back into the stiff leather again will determine our success in making the supple again, right?

You mentioned that "I've had the watch strap sitting in a bottle of linseed oil for the past 2 weeks, took it out this morning, and don't see much of a change. I mean I can bend it a little, but wouldn't go much further for fear of it cracking and breaking."

It seems that the linseed oil is a stuffing oil that has no ionic charging power to hydrogen bond with the leather protein fiber.

Another possible reason is the molecular size of the linseed oil.

If stuffing oil does penetrate by stuffing, it will also leach out and most stuffing oil also produces a darkening effect.

Another con of using stuffing oil is that it clogs up the leather breathing pores that retards natural transpiration for the leather to breathe and the leather often rots out.

To understand how this amphoteric leather behaves, we need to first hydrate the stiff and hardened leather with a water-based surfactant or surface active agent with a pH value within the pH 3 to 5 value of the leather.

This is known as the pre-conditioning process.

And you can have the leather strap sit in the hydrator instead of the linseed oil.

Check the relaxing progress until a satisfying softness is achieved.

You may repeat the soaking with a fatliquor to maintain its suppleness when the leather is dry.

Ultimately, it is the percentage of charged fat and oil in the leather that determines the suppleness of the leather, averaging 14% by weight.

The holistic system to restore leather stiffness is found in this Leather Hydrating and Softening Kit HS3

1: How to Hydrate and Soften Stiff Leather?

1. 1: A holistic 3-step process system to hydrate and soften stiff leather includes pre-cleaning and post-protection.

1. 2.1: Pre-cleaning product systems include Degreaser 2.2, Cleaner 1.5, and Acidifier 2.0.

1. 2.2: Hydrating and softening product systems include Hydrator 3.3 and Fatliquor 5.0.

1. 2.3: Post-protection product system includes Protector B.



https://leatherdoctor.com/leather-hydrating-and-softening-kit-hs3/

You questions are welcome for further discussion.


Roger Koh
Leather Care System Formulator
Consultant / Practitioner / Instructor / Coach
web: www.leatherdoctor.com
forum: www.leathercleaningrestorationforum.com
email: [email protected],
email: [email protected]
phone: 604 773 1878