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Leather Quality and Properties - Page 66

post #976 of 1235
Great discussion. Best one I've seen on SF in a long time. Appreciate your gents' appreciation of science here.

I know glen jay has been busy lately getting acclimated to a new job, but perhaps when time allows he can chime in.
post #977 of 1235
I always prefer more natural solutions to less natural, or petroleum based, solutions.

As pB mentioned, silicone will suffocate your leather as it builds up. Paraffinic hydrocarbons (petroleum distillates) can also suffocate your leather when used repeatedly over time, as well as cause other damage as they break down chemically.

The last Safety Data Sheet I looked at for Nikwax waterproofing wax for leather showed that it contained a fair amount of petroleum distillates.

My preferred method of protecting leather is either wax (like Sno-Seal), or oil (like Obenauf's). For suede I use conditioning shampoo that uses coconut oil for the conditioner.

Silicones, and paraffinic hydrocarbons, in leather weather proofing products are typically very effective solutions for weatherproofing, but are not great for the health and longevity of the leather.
post #978 of 1235
Quote:
Originally Posted by glenjay View Post

I always prefer more natural solutions to less natural, or petroleum based, solutions.

As pB mentioned, silicone will suffocate your leather as it builds up. Paraffinic hydrocarbons (petroleum distillates) can also suffocate your leather when used repeatedly over time, as well as cause other damage as they break down chemically.

The last Safety Data Sheet I looked at for Nikwax waterproofing wax for leather showed that it contained a fair amount of petroleum distillates.

My preferred method of protecting leather is either wax (like Sno-Seal), or oil (like Obenauf's). For suede I use conditioning shampoo that uses coconut oil for the conditioner.

Silicones, and paraffinic hydrocarbons, in leather weather proofing products are typically very effective solutions for weatherproofing, but are not great for the health and longevity of the leather.

Hmmm. The hiking boots I have repeatedly coated in Nikwax are 20+ years old and have been resoled multiple times. It is possible that Nikwax has curtailed their longevity, but not in a way that has had a practical impact to me.
BTW, it smells a bit like vinegar before drying. Anything in the data sheet indicate why that might be?
post #979 of 1235
Quote:
Originally Posted by dopey View Post


Hmmm. The hiking boots I have repeatedly coated in Nikwax are 20+ years old and have been resoled multiple times. It is possible that Nikwax has curtailed their longevity, but not in a way that has had a practical impact to me.

 

I'd be happy with that kind of longevity in a working boot.

post #980 of 1235
As far as I know, Nikwax has changed its formulation over time. Longevity is great, but in this case it would be difficult to interpret.

Glenjay,

What does "suffocate" leather mean? What sort of breakdown do these compounds cause?

As noted above, there are probably thousands of molecules under the classification silicone. Do you know which ones are used for waterproofing? Do they all damage leather? If so, how?
Edited by dbhdnhdbh - 12/29/13 at 8:47am
post #981 of 1235
Quote:
Originally Posted by dopey View Post

Hmmm. The hiking boots I have repeatedly coated in Nikwax are 20+ years old and have been resoled multiple times. It is possible that Nikwax has curtailed their longevity, but not in a way that has had a practical impact to me.
BTW, it smells a bit like vinegar before drying. Anything in the data sheet indicate why that might be?

Quote:
Originally Posted by dbhdnhdbh View Post

As far as I know, Nikwax has changed its formulation over time. Longevity is great, but in this case it would be difficult to interpret.

Glenjay,

What does "suffocate" leather mean? What sort of breakdown do these compounds cause?

As noted above, there are probably thousands of molecules under the classification silicone. Do you know which ones are used for waterproofing? Do they all damage leather? If so, how?

The most recent Safety Data Sheet I have read on Nikwax waterproofing wax for leather is about 9 years old (http://www.osabrands.com/images/products_pdf/Nikwax_Nikwax%20Waterproofing%20Wax.pdf), so it is possible they could have changed their formula since.

It is also important to note that thicker leather like that in hiking and mountaineering boots can take more abuse that thinner leather.

In regard to suffocating leather: So as not to trap perspiration within the leather itself the leather needs to allow some level of moisture to pass through.. Most people underestimate how much their feet sweat. If you want to see how much an unventilated foot sweats just place your bare foot in a plastic baggie and wear it around in your shoe or boot for a day.

Both wax and oil allow for passing a certain percentage of moisture the denser the oil or wax the more impedance to moisture there is. Trapping moisture in leather allows it to more easily oxidize the oils and break down the protein bonds of the leather. This is basically the definition of dry rot in leather. However this does take a while to happen, and even longer in thicker leather.

In regard to petroleum distillates: The basis for all petroleum distillates is the molecular hydrocarbon chain. As the ratio of hydrogen to carbon decreases, and the chain becomes shorter, the molecule becomes more volatile (like a gasoline). Hydrogen atoms can be removed from a hydrocarbon through exposure to UV radiation, as well as other chemically induced means.

In regard to silicone: There are certainly a vast array of silicone compounds, but they all have one thing in common - they contain silicon which is less reactive than its chemical analog carbon. Because of this most silicone compounds are typically heat-resistant, water-resistant and rubber-like. This also means that unlike oil, silicone is much more difficult to flush out of leather, and is also much more likely to smother leather.

There is no requirement of a Materials Safety Data Sheet (MSDS) to list all ingredients, or the ration of ingredients, in a compound; Only those chemicals deemed as hazardous need be listed (as shown in the MSDS for Nikwax in the link above). So, finding the specific silicone compound composition in a given shoe care product would be quite difficult.

I should point out that I am not a chemist by profession, so I am sure there are others here that could give a better explanation in regard to these aspects. I seem to remember that a member that posted in this thread was an actual chemist, and certainly a better source to answer these types of questions.
post #982 of 1235

I have found some data on water vapor permeability through leather treated with silicone compounds. However, it seems that

 

1. The effect is very complicated, depending on the exact silicone formulation used, how  it is applied, how the leather was tanned and fat liquored, whether the silicone was applied during leather manufacture or afterward and how the silicone substance is treated after application.

 

2. Reports of water vapor permeability effects suggest that it is minor with those silicones tested. One mentions a 20% reduction in permeability. Of course, see #1 above, this figures is meaningful only for that particular treatment on that particular leather.

 

There are also reports that waxes and oils also reduce vapor permeability. I have a pair of hiking boots whose manufacturer explicitly said to avoid waxes and oils, and use only fluorocarbon spray to maintain water repellent properties.

 

I suspect that wax and oil effects on permeability is a less interesting current question. The most recent paper I can find on this phenomenon was published in 1950.

 

So far I have not found anything on detrimental effects of silicone on leather other than incompatibility with other treatments. It seems that once the leather it treated with silicone, SOME other treatments will not remain in the leather. From experience, I have treated boots with silicone and then with SnoSeal and they appear to take the beewax as well as boots not treated with silicone. But I did not do any chemistry on them.

 

It is also surprising that I cannot find anything directly addressing the extent to which perspiration leaves the shoe through the lining and then through the outer leather, or by evaporation from the lining surface once the shoes are removed. There is plenty indicating that the lining absorbs water, but the rate of water loss through the upper vs from the lining seems to tilt toward very little getting out through the upper. [perhaps one gram through a single layer of leather during 12 hour day of shoe wear. If that gets the water to the surface of the lining between the lining and the upper, presumably some small fraction of that would make it all the way through the vamp.] Unfortunately, this comes from extrapolations from permeabilities reported for some leather samples and unclear how well it relates to real life shoes. It also does not address the effects of conditioners, polish and waxes on the vapor permeability of the upper. 


For the moment, I am skeptical that any significant amount of water migrates all the way through the lining, through the upper and evaporates from the upper surface during a day's wear. I may try the plastic bag over the shoe trick to see how much accumulates from such evaporation. Rather that put it over the entire shoe, where evaporation around the ankle could confound the results, I think I will place it over the vamp and see whether any dampness appears.

 

I suppose I wonder where the idea that "Silicone damages leather" came from. It might be true, and it is certainly repeated frequently on the internet, but finding hard evidence in support of this idea is proving surprisingly difficult.

 

 

 

re: Nikwax formulation

 

Quote:
 In 2004-5, Nikwax introduced a new and improved active elastomer. The culmination of several years research, these new class of formulations bring better value for money due to increased number of doses from one bottle and an even more durable finish. Unlike fluorocarbon products, you do not need to heat garment to activate the waterproofing treatment. This new class of formulations is being carried across the range, so watch out for even greater performance from Nikwax in the future.

Edited by dbhdnhdbh - 12/29/13 at 2:20pm
post #983 of 1235
Quote:
Originally Posted by dbhdnhdbh View Post

There are also reports that waxes and oils also reduce vapor permeability. I have a pair of hiking boots whose manufacturer explicitly said to avoid waxes and oils, and use only fluorocarbon spray to maintain water repellent properties.

I suspect that wax and oil effects on permeability is a less interesting current question, and I cannot find any original reports on this phenomenon.

So far I have not found anything on detrimental effects of silicone on leather other than incompatibility with other treatments.

For the moment, I am skeptical that any significant amount of water migrates all the way through the lining, through the upper and evaporates from the upper surface during a day's wear.

If you get a shoe or boot soaking wet, how does it dry out? I have lasted boots and shoes that were thoroughly soaked-- lining, heel stiffener and vamp/quarters. Since they are pulled tight to the last and the last is often plastic, how do they dry out? And in only a day or two?

All waterproofing applications be they wax, be they oils, be they mineral oils, silicone, whatever, prevent the transpiration of moisture. If they are applied to keep water out, how can they help but keep water in? And your boots/shoes will always be hotter when treated to repel water.

Now...no disrespect intended but if you are satisfied with the results of your investigations into the "detrimental effects of silicone," why pursue it any further? We both know that in all probability, nothing anyone here can say will convince you. I'm no chemist, Glen's no chemist (although he's a heck of a lot closer than I am).

What is being offered by Glen and others is advice based on real world, hands-on experience across many different situations. Situations that no single individual consumer of shoes is likely to duplicate in a lifetime.

You can find studies on the internet...probably funded by folks with a vested interest...that say silicone is harmless. I have no vested interest either way. Maybe the case could be made that Glen does, but my sense from reading his posts over the years is that he is an honest broker of information.

My experience over many decades and using silicone in lots of different ways and seeing the long term results makes me very cautious about recommending it. I think silicone is strange stuff. I don't think that one application will destroy the leather or detrimentally affect your boots or shoes. But prolonged use on dress shoes in particular will make shining difficult and so load the fibers of the leather with oil (and this is true of any oil but natural oils in particular tend to congeal or oxidize) that you might as well be wearing greasy plastic.
post #984 of 1235
Quote:
 If you get a shoe or boot soaking wet, how does it dry out? I have lasted boots and shoes that were thoroughly soaked-- lining, heel stiffener and vamp/quarters. Since they are pulled tight to the last and the last is often plastic, how do they dry out? And in only a day or two?

A day or two is a lot longer than the 8-12 hours that someone would wear a pair of shoes. The rate of drying is proportional, among other things, to the water content at the start. I can easily believe that the water content would drop rapidly in the first few hours, and more slowly as time goes by. Under the circumstance you describe, I agree that the water in the lining would have to evaporate through the upper. But it does not sound like it happens in 12 hours.

 
Quote:
 All waterproofing applications be they wax, be they oils, be they mineral oils, silicone, whatever, prevent the transpiration of moisture. If they are applied to keep water out, how can they help but keep water in? And your boots/shoes will always be hotter when treated to repel water.

Well, the scientific literature says these treatments work in a manner similar to Goretex. They do not permit liquid water to pass, but they do let the vapor get through. The mechanisms by which they work have been studied for decades. It seems that some of the water motion is through air spaces, some is by tracking along the wet surface of the collagen fibrils. This was discussed in some detail in the old paper

 

"Factors Affecting the Water Permeability of Leather". 1950, Journal of Research of the National Bureau of Standards, 44(4):347. 

 

In fact, there are studies of waterproofing treatments that worked poorly, producing leather that absorbed a lot of water, while not permitting water to pass. See, for example "Comparable Evaluation of Leather Waterproofing Behaviour upon Hide Quality. I. Influence of Retanning and Fatliqouring Agents on Leather Structure and Properties" MATERIALS SCIENCE-MEDZIAGOTYRA  Volume: 18   Issue: 2   Pages: 150-157

 

There are plenty of articles discussing methods of making the various silicone treatments, but none that I have found so far have assessed the longer term effects of these waterproofing approaches on leather durability.

 

Quote:
 no disrespect intended but if you are satisfied with the results of your investigations into the "detrimental effects of silicone," why pursue it any further?

That is just it. I am not satisfied. Many people seem convinced that silicones used for waterproofing damage leather, but so far no one can present any data supporting that, or an explanation of how it works. As I indicated, I have not found any scientific publications that address these issues. Technical papers from manufacturers describe how some silicone treatments work, but they do not discuss whether they could damage leather. The papers published in the scientific literature were funded by national government science foundations, not by chemical companies. So I don't feel that I am anywhere close to an answer as to whether silicones damage leather, if so which ones do this, or how they do it.

 

Quote:
 nothing anyone here can say will convince you.

I am not so much seeking to be convinced as to be pointed toward some scientific evidence. I don't need someone to tell me "the answer", I am just hoping someone knows of studies that had attempted to answer these questions, and where they were published.

 

Quote:
 is advice based on real world, hands-on experience across many different situations. Situations that no single individual consumer of shoes is likely to duplicate in a lifetime.

That is certainly valuable, but I am looking for the underlying science. Particularly with respect to silicone, that covers such a range of substances that it would seem hard to generalize the effects.

 

Why do I bother to ask?

 

Mainly curiosity, but I suppose the answers could have some influence on choice of waterproofing compounds to use on my leather.

post #985 of 1235
Fwiw, I don't think Nikwax uses silicone. On their website they say they use a compound that includes modified forms of EVA (ethylene-vinyl acetate) and mineral wax. I've used their products for years on Gore-tex jackets and pants, but haven't tried their boot stuff. For waterproofing boots, I used mink oil for decades and switched to Sno Seal about five years ago based on Crane's recommendation here.
post #986 of 1235
Quote:
Originally Posted by DWFII View Post

Warning: Spoiler! (Click to show)
If you get a shoe or boot soaking wet, how does it dry out? I have lasted boots and shoes that were thoroughly soaked-- lining, heel stiffener and vamp/quarters. Since they are pulled tight to the last and the last is often plastic, how do they dry out? And in only a day or two?

All waterproofing applications be they wax, be they oils, be they mineral oils, silicone, whatever, prevent the transpiration of moisture.
If they are applied to keep water out, how can they help but keep water in? Warning: Spoiler! (Click to show)
And your boots/shoes will always be hotter when treated to repel water.

Now...no disrespect intended but if you are satisfied with the results of your investigations into the "detrimental effects of silicone," why pursue it any further? We both know that in all probability, nothing anyone here can say will convince you. I'm no chemist, Glen's no chemist (although he's a heck of a lot closer than I am).

What is being offered by Glen and others is advice based on real world, hands-on experience across many different situations. Situations that no single individual consumer of shoes is likely to duplicate in a lifetime.

You can find studies on the internet...probably funded by folks with a vested interest...that say silicone is harmless. I have no vested interest either way. Maybe the case could be made that Glen does, but my sense from reading his posts over the years is that he is an honest broker of information.

My experience over many decades and using silicone in lots of different ways and seeing the long term results makes me very cautious about recommending it. I think silicone is strange stuff. I don't think that one application will destroy the leather or detrimentally affect your boots or shoes. But prolonged use on dress shoes in particular will make shining difficult and so load the fibers of the leather with oil (and this is true of any oil but natural oils in particular tend to congeal or oxidize) that you might as well be wearing greasy plastic.

Liquid water and water vapour are two different animals.
post #987 of 1235
There was that weird experiment posted on here, or the shoe care thread with that Asian guy that polished one of his shoes with an insane amount of kiwi and the other with just a little bit and ran on a treadmill or something for a while. Then his feet were put in these glass boxes that measured humidity and the shoe with more wax on it was emitting less water vapor because it was encased in so much wax.

I don't think anybody is saying silicone is inherently bad for leather. It is in like 99% of cosmetics and is inert. I believe many women are known to have it placed in their breast cavities. I think the issue arises with repeated use over time; the build-up that occurs and the effects of the build-up on both leather health and appearance. The effect over time isn't endemic to silicone, but anything that is repeatedly applied to leather over time. I think the issue that is endemic to silicone is the fact that they aren't nearly as soluble as many other shoe products, especially natural ones so when they are applied they are there to stay unless some sort of harsh method is used that will inherently damage the leather like a detergent, mineral spirit, or acetone.

I am a bit of a fuddy-duddy when it comes to cosmetics and such and one thing that I have learned over time is the fact that sulfates are used has foaming agents for cleaning. Essentially detergents in probably 98% of hair, hand, body washes (and even a lot of conditioners). This is an artificial soap, a detergent, made by the German's during WWII (supposedly according to my high school Physics teacher) when natural castile soap had run out and became hard to get a hold of. Th point I am making is that all of the silicones in hair and skin products that makes us feel smooth is washed away from these harsh detergents using sulfates. If you look online at the nerdy hair and skin community forums (think Style Forum for hair and skin stuff) they say if you are switching to natural soap you should switch to natural conditioners and lotions and such because the natural soap won't ash away all of the silicones in the other products and it will clog your pores, make you feel kind of matte and waxy and make your break out. Essentially, it will keep building up. Logically thinking about it the effect of silicones on leather would be very much the same. Do you see this happening in the wild? If not, awesome keep using them, but if you can avoid using them at the very least for peace of mind you don't have to change your behavior in the slightest, just change the product. Personally I am all about peace of mind without any change in behavior, seems like a win-win to me.
post #988 of 1235
Quote:
Originally Posted by Fang66 View Post

Liquid water and water vapour are two different animals.

Surely not as extreme as all that. Are they not both H2O? One matter in two different states, perhaps.

It may be worth noting that when water is used or required for lasting shoes or boots it can be applied by immersion, spritzing or in steam cabinets (the preferred commercial approach). Same results, no harm no foul.

Perhaps of interest also...and more to the original point...is that when a wet boot is lasted some small amount of moisture is expressed (squeezed out) but the most of it remains. And the only way it dissipates is by evaporation--the self-same mechanism that allows moisture from the foot to transpire through the leather to the outside.

Now I'm no chemist or scientist...just a simple country shoemaker who has seen this process many times...so take it for what it's worth.

cool.gif
post #989 of 1235

Liquid water and ice are both H2O.  Same molecule in two different states.  Just sayin'.

post #990 of 1235
Quote:
Originally Posted by DWFII View Post

Quote:
Originally Posted by Fang66 View Post

Liquid water and water vapour are two different animals.

Surely not as extreme as all that. Are they not both H2O? One matter in two different states, perhaps.

It may be worth noting that when water is used or required for lasting shoes or boots it can be applied by immersion, spritzing or in steam cabinets (the preferred commercial approach). Same results, no harm no foul.

Perhaps of interest also...and more to the original point...is that when a wet boot is lasted some small amount of moisture is expressed (squeezed out) but the most of it remains. And the only way it dissipates is by evaporation--the self-same mechanism that allows moisture from the foot to transpire through the leather to the outside.

Now I'm no chemist or scientist...just a simple country shoemaker who has seen this process many times...so take it for what it's worth.

cool.gif

liquids and gases behave differently when faced with a semi-permeable membrane.
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