Leather Quality and Properties



Munky said:

Thank you, DWFII for your detailed and - as always - helpful reply. It was enlightening. 

In my message, I had written a line about 'do Saphir products really make a lot more of a difference to shoes than, say, Meltonian. - but I deleted it. From what you write, I suspect that one answer to that question might be 'not a lot of difference'. Is the difference almost just a marketing ploy?  Just as people may buy 'label' clothes, imagining that they are getting something better and feeling somehow superior to those who buy ordinary clothes? 

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I don't think the differences are that significant, especially when you're considering what solvents are being used, etc.. One may have more carnuba, and other product may have more pigment.

It's only when things like mink oil, mineral oil and silicone start entering the recipes that I get nervous. I used to think that Meltonian was just re-branded Properts (or vice versa.) I don't know, I would gravitate towards more Traditonal and natural products, if I had a choice and knew for sure what the formula was.

Is it a "marketing ploy"? What isn't?At a certain point...as I've said many times...it isn't about quality anymore (if it ever was), it's about profit.

"A maker has to choose--whether to make shoes (read 'quality') or to make money...because you can't do both"--DWFII

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To the extent that products fall from grace or start experiencing difficulty with things like colour and oxidation and/or separation in this context, it's almost always because at some level choices were made to substitute relatively expensive raw materials or techniques for cheaper ones.

Thanks, again, DWFII, that's helpful info.

In 1997, Prof. Tsunoda examined chemical analysis values (water content, total ash content, chromium content, etc.), mechanical properties (thickness, tensile strength, tear strength, etc.), and physical properties (water resistance, water vapor permeability, water absorbency, etc.) of calfskins and steerhides used for shoe uppers.
http://www.hikaku.metro.tokyo.jp/images/pdf/121pdf/04.pdf
http://www.hikaku.metro.tokyo.jp/images/pdf/122pdf/03.pdf

I excerpted water resistance and water vapor permeability from her paper. Water resistance here means the penetration time of water column from the grain side to the flesh side. This paper shows some resin finished leathers (sample nos. 2, 8, 9, 10, 13, 14, 15, 18) will absorb shoe creams well, but corrected grain leathers (sample nos. 16, 17, 19, 20) usually won't absorb them.





http://www.trespass.co.uk/p/739/technology




Here are Norwegian welts/Norwegian stitched soles.

http://forthediscerningfew.com/2011/12/03/john-lobb-bootmaker-part-iii/



http://forthediscerningfew.com/2011/11/26/john-lobb-bootmaker-part-ii/






http://news.google.com/newspapers?id=MXYxAAAAIBAJ&sjid=_yEEAAAAIBAJ&pg=2134,2246096

The Japanese love doing experiments, don't they?

What is boxcalf?

On balance, I think I prefer the $6 Regal shoes...

VegTan said:

CH2 next to a double bond is called an active methylene group, while CH2 is called a methylene group. A methylene group is stable, but an active methylene group is considered to be susceptible to ultraviolet and/or heat. (Why "is considered"? I guess it is difficult to verify it experimentally.) Here is a reference: http://books.google.com/books?id=Hcl0fkcrfbEC&pg=PA856&hl=en

This new free radical "#B" goes back to "#reaction", which is called a chain reaction (autoxidation). Hydroperoxide "#A" is decomposed into aldehydes, ketones, alcohols, and polymeric compounds. Aldehydes, ketones, and alcohols are causes of bad smell and change in color. Polymeric compounds are a cause of increase of viscosity.

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VegTan said:

I learned alcohol oxidation (http://en.wikipedia.org/wiki/Alcohol_oxidation , http://en.wikipedia.org/wiki/Dehydrogenation) as an example of a dehydrogenation reaction, and I read some books and dictionaries, but they didn't refer to dehydrogenation of petroleum distillates. I thought a dehydrogenation reaction needs a chemical plant/laboratory. Could you tell me the book/paper which refers to dehydrogenation of petroleum distillates?

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It would be the same mechanism as the one for ***** acids; they're both pretty much the same thing, except ***** acids have a carboxylic acid group at one end which doesn't participate in this reaction anyway. It is done industrially in a chemical plant, but that uses a catalyst instead of sunlight to make the reaction happen a lot faster.

I wonder if they use optimal ratios of saturated/unsaturated oils in shoe care products. On the one hand, unsaturated oils would make it easier to use as it becomes less viscous, but on the other hand unsaturated oils have more stable radicals and thus have more chance to react in sunlight, forming undesired products.

(P.S. I'm a chemist and biochemist, so any questions, send them my way)



mezentius said:

(P.S. I'm a chemist and biochemist, so any questions, send them my way)

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So if the doctor tells you your triglycerides are high and you eat tons of foods that are basic on the pH scale will you get really soapy blood?



patrickBOOTH said:

The Japanese love doing experiments, don't they?

What is boxcalf?

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I think the American also do experiments.
http://www.astm.org/Standards/leather-standards.html

Box calf is a leather tanned only with chromium salts, while some leathers are retanned with vegetable and/or synthetic tanning agents.

http://www.iultcs.org/leather_terms/b.asp
Box calf
Full chrome tanned calf leather, black or coloured, smooth or boarded.
Note: In the UK it must be black. When it is in other colours, see willow calf.

http://www.iultcs.org/leather_terms/w.asp
Willow calf
Calf skin leather, coloured, commonly brown, usually with a typical willow grain or with a box grain pattern. Full chrome tanned and boarded either in one direction - head to tail - or in two directions, as with box calf.

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http://weinheimer-leder.com/productrange/productdescriptionboxkalb/index.html
Box Calf
Tanning - classic chrome tanning

http://weinheimer-leder.com/productrange/michigan-calf/index.html
Dragon Calf
Tanning - classic chrome tanning, vegetable retanning

http://weinheimer-leder.com/productrange/odessa-calf/index.html
Odessa Calf
Tanning - classic chrome tanning, syntetic-vegetable retanning

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mezentius said:

(P.S. I'm a chemist and biochemist, so any questions, send them my way)

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Thank you. Are petroleum distillates dehydrogenated by ultraviolet and/or heat of sunlight?

What's the advantage of chrome only tanning? Does it look different? Behave differently? My guess based just on reading over the years is that chrome tanning lends to a more malleable leather as opposed to veg tanning. Is the only "benefit" of re-veg-tanning rigidity for certain applications?



patrickBOOTH said:

What's the advantage of chrome only tanning? Does it look different? Behave differently? My guess based just on reading over the years is that chrome tanning lends to a more malleable leather as opposed to veg tanning. Is the only "benefit" of re-veg-tanning rigidity for certain applications?

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Here is some information.

http://www.pcst.org.pk/journal/JN/2...ilization of starch in leather processing.pdf

Retanning of leather fills the looser areas of hides and skins and improves the leather properties, such as softness, fullness and grain smoothness.

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http://horween.com/101/chromexcel-2/

Next comes retanning, and it’s where the secrets begin. Specific and proprietary mixes of bark extracts and natural agents are used to give Chromexcel, and many of our leathers, its heavy vegetable retannage. The benefit of combination tanning comes from the specific attributes that both chrome and vegetable tanning impart. Generally, chrome tanned leathers yield soft, supple, and durable leathers, while vegetable tanned leathers are round and full feeling, patina well, and are easy to coax into shapes using heat and moisture.

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For example, chrome tanned leather needs to be retanned to emboss it, because it has less plasticity. Some retanning agents may improve the tensile and tear strength, while I don't have the direct evidence.

Chrome tanned leather has better breathability and anti-mold property, which would be an advantage.
http://archive.org/details/jresv44n4p347

http://cool.conservation-us.org/coolaic/sg/bpg/annual/v21/bp21-21.pdf

Chrome tanned leather does not mold as easily as a vegetable tanned leather

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The lower leather is Chromexcel which is heavily vegetable retanned. The color of the cross section looks like vegetable tanned leather.
http://ameblo.jp/emptyg/entry-11081296280.html



Combination tanned leather (Chrome retanned leather) appeared around 1930, AFAIK. Here is the then news.

http://books.google.com/books?id=gS...cfVkAWv34HACQ&redir_esc=y#v=onepage&q&f=false


http://news.google.com/newspapers?id=KChiAAAAIBAJ&sjid=KXYNAAAAIBAJ&pg=4018,3712748


The details are here.
http://naldc.nal.usda.gov/catalog/CAT86200163
http://archive.org/details/jresv15n4p363


Wolverine used to have own tannery and was famous for triple tanned uppers and soles.
http://www.ebay.com/itm/1950-vintage-ad-for-Wolverine-Shoes-3074-/360736315260

patrickBOOTH said:

So if the doctor tells you your triglycerides are high and you eat tons of foods that are basic on the pH scale will you get really soapy blood?

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Nope, the base will get neutralised in the stomach before it can reach the bloodstream. In any case, acatalytic base hydrolysis is really slow anyway at body conditions.

/NOFUNALLOWED

VegTan said:

Thank you. Are petroleum distillates dehydrogenated by ultraviolet and/or heat of sunlight?

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Depends on which ones. The crucial difference again is the number of double bonds in the molecule, exactly analogous to the rules you posted for biological ***** acids. As a rule of thumb, straight chain petroleum distillates should be more susceptible to dehydrogenation as they increase in size and in the number of double bonds. It's a bit of a bother to search for papers on the topic, though, as the UV seach term brings up mainly characterisation techniques instead of reaction mechanism.

I vacillated between this and the shoe care thread but I thought this might be more pertinent since my question is about leather, specifically the uppers. I recently move to MI where the winters are pretty cold. I was thinking of storing my shoes in the garage but I am hesitant because I do not know how well the uppers will tolerate the winters. Unfortunately, I do not know exactly how cold the winters get here (let alone the temperature in the garage which I assume will be slightly higher) but I think they fall around the teens (F).

Any thoughts?

Is Michigan Relative Humidity Map true?
http://www.usairnet.com/weather/maps/current/michigan/relative-humidity/

Unless your garage is air-conditioned, high relative humidity is dangerous for leather.

http://cool.conservation-us.org/waac/wn/wn19/wn19-2/wn19-209.html

1. RH, temperature, and associated effects on moisture content
The average moisture content of leather is 15%. RH above 75% can cause mold growth and swelling of the leather fibers, whereas RH below 25% can cause shrinkage of the skin. A combination of dryness and heat can cause irreversible deformation of the skin. Cycling of temperature and RH can lead to the development of stress fractures and cracking. Persistent low temperatures (below 12 degrees C) can solidify the fats present in the skin and cause formation of spew on the leather surface. High temperatures will cause dryness and embrittlement, and may also turn skin oils rancid. Water damage can cause the migration of soluble tannins to the surface of leathers, where they cause darkening and hardening of the skin. Deteriorated leathers are particularly susceptible to this effect, the fibers being more likely to collapse and stick together.

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So what's the best way to care for leather if you have high humidity and no air-conditioning?

I would say the best thing in that case would be plenty of rest with shoe trees in between wearing so the leather can naturally dry out from sweat. I would condition after it gets worn a few times ~6 wears. Light brushing in between wears.