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Recently two different clients forwarded pictures of their white leather furniture.  In both cases the symptom was the same.  A yellowing discoloration of the leather.  Here are two pictures.

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In both cases the client put a skin cream on their legs and then sat in the leather seating.  The skin cream has coloring agents that will act as synthetic tanning agents.

As the tanning agent is a dye, it transfered from the occupant's skin into the leather, discoloring as shown.  There are no warning labels on the skin cream container.  Yet it will permanently discolor the color coat.  It would not be an issue on a dark leather as you wouldn't see the discoloration.  However on a light colored leather it is clearly a problem. 

It is not a cleaning issue as the leather has literally been recolored, just as was intended for the person's skin by the lotion with this tanning additive.  Trying to clean it is like trying to clean a tattoo from your skin.  

The correct solution is to match the color and color over the offended area.

Upholstery grade leather has about 25% moisture content as it leaves the tannery.  This moisture content is typically natural oils like neetsfoot that is infused into the fiber structure imparting suppleness.  These oils are volatile, meaning they evaporate away overtime at a rate dependent on the humidity.  If you are in a very dry climate and the leather is exposed to direct sun or other heat source then the evaporation rate is considerably accelerated compared to a damp climate or where the leather is not exposed to a direct heat source like the warming sun.

As moisture evaporates from leather two things happen: 1. the leather shrinks due to lose of mass, and 2. the leather looses is internal lubrication.  In either case the affect is stiffening.  At some point, where the moisture content drops below 5% or so, the leather feels and behaves like a piece of cardboard.  This is its demise.

Leather conditioners contain replenishing oils.  The goal of conditioning leather then is instill lost oils to keep the moisture content elevated.  Consequently, this simple maintenance procedure prolongs the leather’s life.  It’s a pretty simple concept.  However, there is more to the story.  Here are some important considerations:

pH Issue.  pH measures acidity or alkalinity.  The range is from 1 to 14 with pure water being neutral at 7.0.  Leather is acidic.  It measures 4.5 to 5.0 on a pH scale.  Furthermore, the pH scale is logarithmic, meaning that each whole number is 10 times more or less acidic or alkaline than the next number in the scale.  When you mix two elements that have differing pH, a chemical reaction occurs.  In the case of leather, this chemical reaction accelerates the breakdown of leather fibers.  Therefore, any conditioner applied to leather should be pH balanced to leather so as not to damage the leather.

Coated (Pigmented) Leather.  Most leather has a surface color coating.  This coating is also covered with a clear coat providing protection and wear resistance.  So, if something spills on the leather, it is easily wiped up without penetrating and staining the leather.  These coatings are generally chemical engineered to have a certain degree of porosity, allowing the leather to breath.   However, the ability for a conditioning agent to penetrate through this protective barrier is a challenge.  This is particularly true with automobile grade leather.  For automobile leather, the most effective procedure is to warm the leather up a bit (leave the car in the sun for a few hours) before you apply a conditioner.  Warming the leather reduces viscosity allowing a higher absorption potential. Then, aggressively massaging the conditioner into the leather will help.

Over conditioning.  If a little is good, then a lot must be better, right?  A common mistake is to apply too much conditioner.  Think of a sponge fully laden with water.  Adding more water is not possible.  This is also true with leather.  If the moisture content is at its maximum, then adding more conditioner does nothing except to sit on the leather surface, drying over time and turning sticky and gooey.

Old, Desiccated  Leather.  If old leather has lost most of its moisture then it can be a huge mistake to attempt to revive it by adding conditioner (moisture).  Think of a piece of cardboard that gets wet.  It turns the cardboard fibers to mush.  The same is true for leather.  If your leather is old and dried out, the best strategy is to leave it alone and consult a professional.  There are specific chemistries that can be used to prolong the life of old leather.  The run-of-the-mill conditioner is not one of them.

When to Condition.  As in over conditioning, if the leather is new, then it has a full compliment of moisture.  There is no reason to condition as it hasn’t had time to loose its moisture.  As a general rule, begin conditioning leather after 6 months to a year.  And then re-apply every 3 to 6 months depending how dry the environment.  In certain cases a more frequent regimen is appropriate like in the summer months of a desert climate.

How to Apply.  Generally, a thin coating is sufficient. Apply the conditioner to a soft cloth, massaging into the cloth and then wipe over the target leather. If the leather is heavily coated, then massage the leather with the conditioner.

Leather That Should Not Be Conditioned.  Be very careful with suede or nubuck leather.  While they will loose moisture as well, conditioning them in a standard procedure runs to risk of staining the leather.  It can leave the leather looking blotchy, thus destroying the aesthetic appeal.  Additionally, delicate leather like calf or lamb skin should be treated cautiously. 

The most important consideration is to be sure that you are doing the right thing with whatever maintenance products you use on leather.  In the end it's always wise to consult with a professional.

We are often called upon to save existing leather, despite the reality that the leather is technically at the end of its useful life.  The typical life cycle of quality leather runs about 30 years.  However, we’ll be asked to restore leather that is 50 to 100 years old or even older where the leather is severely desiccated, with deep epidermal damage.  These projects move beyond typical restoration and into the realm of conservation and preservation. They are the assignments where the true skills of our craftsmen come into play.  

Sometimes we have to invent processes to accomplish the client’s goal.  Saving the leather interior built into a 1953 Jaguar XK-120 is an excellent example. By any reasonable measure the leather was beyond restoration yet the client wanted to retain the original leather for valuation purposes.

Because this was a unique project, we documented the process via video.  We also knew it would be a long term project and the client lived 1,500 miles away, so video documentation was a method we used to keep the client informed of our progress.  You can access the full video from your web-site directly by clicking on the link at the bottom of this post.

The following is a copy of a letter the client sent to Auto Restorer magazine, a periodical dedicated to the classic car crowd.

Dear Auto Restorer,

I’ve been a subscriber for several years and would like to alert your readers to what I believe is a relatively unique service that will be of interest to anyone wanting to preserve an original car versus restoration.  I’m the fortunate steward of an unrestored 1953 Jaguar XK-120.  My 58,000 mile car’s original paint still looks nice, albeit with a few blemishes here and there, and mechanically is trustworthy as well.  The leather seats however were deteriorating to the point that in order to save them at all, I pulled them out and for the last couple years substituted a pair of reproductions of period competition seats.  For several years I looked for someone who could repair and preserve the original leather versus going the route of an upholstery kit.  These were beyond a minor Dr. Vinyl type repair as there was serious scuffing in places and several cracks that had grown into full splits.

I periodically searched services every year or so and last fall found Advanced Leather Solutions in the San Francisco Bay area of California.  My seats were in their shop a few months as the process for removing oils to get the leather where they can bond repair panels under the surface requires many applications over time.  Along the way, they sent video updates so I could see everything that took place.  Anyone seeing the before and after would be amazed.  The scuffing, open cracks and splits are gone yet they maintained the patina that only time can bring.  As you’re probably aware, preservation instead of restoration is a growing trend in our hobby and in my opinion this company is a great resource for anyone who wants to repair and preserve original leather.  For those interested, a video of the processes performed on my seats can be downloaded from their web site at www.advancedleathersolutions.com.

Thanks,

Mike Buchanan

Cape Girardeau, MO

It is projects like this that sets Advanced Leather Solutions apart from the ordinary leather repair and restoration company.  While our bread and butter work is the mundane repairs and restoration, our true skills are tested with the out-of-the-ordinary projects.  They create the opportunity to extend the boundaries of our technical and artistic abilities. 

We are seeing more and more of this from our clients who want to preserve and conserve old leather --- to keep that “look” yet resolve the problems life presents.  For example, a current project involves water damage suffered on century old dining chairs where the leather on the seat tops is structurally disintegrating.  Our goal is to artistically conceal the water damage without causing further deterioration to the leather.  This is truly a challenge.

If you want to learn more about the conservation and preservation aspects of leather restoration, feel free to contact us.      

This is the link to the video of the Jaguar XK-120 project:

http://advleather.com/xk120vid.html

For years I've taken phone calls and e-mails from distraught consumers who made the mistake of purchasing bi-cast (bicast) material when they thought it was real leather.  It is sold as leather but it is clearly NOT the real deal.  Just as fiberboard isn't real wood, bicast isn't real leather. As a general rule, leather that has suffered damage can be successfully repaired.  In the case of bicast this is problematic as any repair can only be as strong as the surrounding material.  With bicast, the material is inherently weak.  As such, a repair to bicast will, in all likelihood, fail. At the end of this blog entry you'll find a link to photos that have been sent to me by consumers depicting their  classic problems with bicast material.  They show the wide variety of ways bicast fails.  In the world of furniture there has never been a more true application of the phrase "buyer beware."  Bicast is a problem waiting to happen. Here is the text of an excellent article written by Barbara Carney, a leather restoration expert in the Chicago area.   Bi-cast and Bonded Leather is NOT Leather! So, What Is It? . "Bi-cast and bonded "leather" can be the right choice for you – Here’s the complete story so you can make an informed decision. "The term “leather” is used to describe 2 completely different types of material used on furniture: 1.      Real = An intact animal hide processed to look and feel good. Very strong. 2.      Bi-cast / bonded = Plastic with a little leather and maybe some fabric glued to the back. Not so strong. "Note: Imitation leather = Plastic with fabric glued to the back. Not so strong. "What’s going on? Leather’s very desirable because it: · Looks good - many different possible textures, colors and finishes · Strong, durable – can last decades; can be repaired and recolored · Feels good to touch – soft and flexible · Breathes, so you don’t get clammy or too hot · Shows you have taste and could afford the nicer things "Real leather soils easily, so a protective paint-like colored coating is added to approx 85% of the real leather furniture sold in the U.S. It’s a thin, breathable plastic that stays flexible and still has an appealing leather feel and light smell. Consumers easily confuse this with the thicker, non-breathable plastic layer of the lower cost bi-cast and bonded leathers. By adding a little leather – about 17% - which you don’t see or touch, it’s legal in the U. S. to sell bi-cast and bonded products as leather – which most people will think means real leather. In Europe and New Zealand it’s illegal to call such products leather. "Bi-cast is a clever product. Typically, it’s a thick layer of plastic made to look and feel like leather, laminated on top of a thin, weak layer of leather. This layer is a “split” - horizontally split from the bottom of the original hide in a big sheet. In bi-cast, you don’t see it or feel it. It adds none of the characteristics of real leather, except one: If you check the inside surface, it looks and smells like leather. Why bother? A savvy consumer may know how to check for real leather by looking at the inside for the characteristic rough suede and the smell, or a trained salesperson may show it to the consumer – “See – it’s leather!” "Bonded leather goes one step farther: Powdered leather fibers are mixed with a resin and extruded in a sheet, like paper or particleboard. There’s no physical characteristic left of the original leather. It’s a recycling method for using scraps. Just like the asphalt on your street might contain recycled plastic bottles. The layer containing the leather is on the back, just like bi-cast. "As Furniture Today magazine says: ...calling these products bonded leather "is deceptive because it does not represent its true nature. It's a vinyl, or a polyurethane laminate or a composite, but it's not leather. If you tar and feather someone, does that make them a chicken?" Obviously not.  "Sometimes it's even scented like leather.  In the end, it's plastic  - it's clammy, it's much less durable, it can't be repaired - unless you consider duct tape and a slip cover a repair. Some split or delaminate and peel after a few months or just a year or 2.  Some are more durable, but it's very hard to know when you buy it. You’d need the test data on the number of  “rubs” to be sure."

Thank you Barbara for this excellent piece.  I hope it will help alert the unsuspecting consumer to make wise choices when selecting their leather furniture.

Click on this link to see pictures representing a sampling of the problems bicast presents.

http://picasaweb.google.com/kpgillan/BicastPicturesFromClientsShowingTheVarietyOfWaysBicastLeatherFails#

There is a common misuse of the word “dye” in the leather repair and restoration business.  While I’ve discussed this before here, it’s time to address the issue again. 

There are two methods for coloring leather.  1. Dyes.  2. Dyes and then pigment coated.  It is very rare that leather would be pigment coated without having been dyed first.

Starting with the basics – Animal skins are tanned.  This process converts the skin to leather.  The main purpose of tanning is to preserve the hide.  It stops the natural degeneration or rotting process.  At the end of the tanning procedure and before the color step, the hide is called a “crust.”

The crust is highly absorbent. Think of a chemise. The crust is infused with a dye which we all know to be a coloring element.  The actual dye molecule is very small.  It penetrates into the fiber structure of the crust (leather) and establishes the color.  Typically it penetrates completely through the leather (struck through) so looking at a cross cut, you see the same color from front to back.  The dye is not molecularly bound to fiber structure, rather it as floating within the fiber bundles.  Because it is free floating, one of its attributes is migration.  It will transfer or move. 

Water will accelerate migration.  Consider blue jeans.  They fade when washed.  The dye molecule migrates out of the medium (in this case denim) and is flushed down the drain.  I have had occasion to witness this phenomena with leather many times.  A damp white cotton cloth wiped across dyed leather will pull the color.

Dyes have a unique beauty.  Because of their small molecular construct, dyes are translucent.  You look into the leather to see its color.  It accentuates the natural beauty of the leather. Because the porosity of leather is inconsistent, some areas of the hide will accept more dye than others.  This creates the natural mottling affect you see with dyed leather.  Its beauty can’t be beat.  We classify this leather as being “unfinished.”

There is a dark side.  The dye molecule does not tolerate UV light very well.  That wave length or spectrum of light hits the dye molecule and breaks it up.  This process gradually leaches the dye from leather causing the leather to lose its color (fade).  Furthermore, dyed leather continues to have a high level of porosity.  Spill a liquid and it will soak into the leather, potentially staining the leather.  In reality the stained area has been re-colored.  So trying to clean it is like trying to clean a tattoo from your skin.

Bottom line: dyed or unfinished leather is beautiful when new, but it is aesthetically vulnerable to staining and fading.  Only about 15% of all leather furniture is unfinished.  It is typically the most expensive leather as only the finest hides (least flawed with unsightly hide characteristics) can qualify to be unfinished.

Most leather then goes through a secondary coloring process with the application of a pigmented coating.  The pigment molecule sits on the leather’s surface.  As a coloring element the pigment molecule is a big, robust molecule with excellent covering power, like snow on the ground.  The pigment molecule is carried in a binding chemistry that locks it in place.  That binder chemistry is uniquely engineered for leather.  It establishes a film on the leather surface that is opaque.  The color you see is from a topical colorant that is a pigment.  This is known as “finished” leather.  

Pigments lack translucency so the color is flatter than dyes.  But pigments are far less sensitive to UV so they don’t fade nearly as radically.  Consider and automobile leather car seat. They don’t fade despite tons of sun exposure.  They are colored with a pigment.  Additionally, the film of color on the leather will resist absorption. If something spills, you can wipe it off the leather as it won’t immediately soak in.

You can not successfully re-dye leather using dye as the coloring element for a whole bunch of technical reasons, not the least of which is that you will be wearing the color on your clothing if you sit on the furniture.  Setting the dye so that it doesn’t transfer easily can only be done at a tannery under very specific and controlled processes.   

Leather can be re-colored, but only with a pigment application.  If it was dyed (unfinished) leather in the first place, the re-coloring process is with a pigment that provides full covering power, thus converting the leather to a “finished” or pigment coated status.

Of course we do this color restoration process professionally all the time, and it is the essence of the Do-It-Yourself kits offered by Advanced Leather Solutions.  Taking it one step further, because it’s an opaque chemistry, the color coating can be changed to whatever color desired.

When doing a full color restoration to leather furniture, automobile leather or garments there are two application options with Advanced Leather Solutions color system – rub and spray.  But, which is best?

There are clear pluses and minuses to both.

Spray System with High Volume Low Pressure (HVLP) Air Equipment:

Advantages  

      Even color application

      More efficient use of material – less waste

      No potential for streaking

      More “factory like” result

      Less labor intensive

      More variety of mottling techniques if required

Disadvantages

      Over spray considerations

      Must tape-off all not leather components

      Must have expensive equipment (Compressor and Air Gun)     

      Not practical for in-home application due to over spray 

      Requires top-coat as sealer coat

Rub System with Wipe-on Color Applicators

Advantages

      Simple 

      Easy to master the application technique 

   Does not require experience

      Single pass - does not require a top-coat

      On-site application does not require taping-off

Disadvantages

      More material consumed 

      Takes longer – more strenuous 

      Potential for streaking 

      Not as fine a finish as spray

In the end, both systems produce excellent results.   The choice of one over the other is often dictated by the nature of the assignment and availability of application tools.

 For a consumer, the rub system is better suited as it’s so simple to master and doesn’t require specialized application equipment.  For the professional leather technician the rub system offers the ability to work on-site with no threat of over-spray issues.

In a professional shop environment the choice is generally to spray as it more efficient use of labor time and materials and will produce a finer, more factory like result.

In our shop we use a hybrid approach.  In either case leather has to be properly primed for quality adhesion.  Then, we spray a section of leather with one hand and wipe it while wet with the other.  This mechanical wiping motion promotes better adhesion as it drives the color down into the grain pattern.   We then spray each subsequent coat to create a smooth, even color distribution, followed by topcoat application applied via spray.  Here is a video link to YouTube that shows a color change in our Hayward, CA leather restoration studio.

http://www.youtube.com/watch?v=ycZhJTSrKJ0

Both approaches have their place.  Our rub system has worked wonders with consumers, empowering them with the ability to restore their own furniture using the Advanced Leather Solutions’ Do-It-Yourself kit concept - a rub based solution. Check it out at this web-site:

http://www.DIYLeatherSolutions.com  

Our professional leather technician clients have generally standardized on the spray approach.  However, some use both depending the circumstances.  For example, Leather Doctor in the Columbus, Ohio area uses both --- the rub approach when doing in-home restoration and the spray option in his shop facility.

To learn more about the art and science of leather restoration contact us at Advanced Leather Solutions or go to our web-site http://www.advleather.com.

In the September, 2010 issue of the popular magazine Martha Stewart Living there is an article that talks about how to clean various household items.   One of the categories discussed is leather.  In the article it is recommended to use household cleaners on leather.  This is a serious mistake that can easily discolor or worse permanently damage fine leather furniture.

A minor lesson in basic chemistry will make this problem clear.  It has to do with a not well known leather attribute – the pH of leather.

What is pH anyway? 

pH is a measure of the acidity or alkalinity (basicity) of a substance.  It is measured on a scale that runs from 1 to 14 where the center point --- 7 --- is neutral as determined by pure water.  Any measure below 7 is acidic and any measure above 7 is alkaline.  This scale is logarithmic.  This means that a substance with a pH of 6 is 10 times more acidic than water (pH of 7) and continuing down the scale, a pH of 5 is 100 times more acidic than water.  The same differential applies going up the scale as well.

When you bring two substances into contact with each other where their pH differ, a chemical reaction occurs as the pH of both substances come into balance by neutralizing each other creating a salt like substance in the process.  The severity of the chemical reaction is determined by the degree of differential.  Mix baking soda (a Base) with vinegar (an acid) and a somewhat explosive chemical reaction will occur.  There are several videos on YouTube that clearly demonstrate this reaction.

How does this apply to leather?

Leather is acidic.  Its pH is measured at between 4.5 and 5.0.  Household cleaners are alkaline.  Windex, 409, Mr. Clean are all common household cleaners with a pH of exceeding 9.0 and topping out at 11.45 (Windex).  Given the logarithmic nature of the scale, that represents a huge differential compared to leather.

Like in the vinegar and baking soda demonstrations, a reaction within the fiber structure of leather occurs when you clean leather furniture with a household cleaner. Leather is a very absorbent material.  It may not be as immediate or as explosive but the reaction nonetheless will slowly but permanently damage the leather’s fiber structure, weakening it in the process.  As the household cleaner is absorbed into the leather fibers the reaction breaks down those fibers.  With enough exposure, the fiber bundles lose their integrity, turning to mush.  Bottom-line: household cleaners accelerate the demise of fine leather furniture.

The other negative is the effect these harsh cleaners can have on the color coating of “finished” leather.  It acts like a stripping agent, pulling the protective clear coating and subsequently color coating as well.

As a leather repair and restoration specialist with Advanced Leather Solutions, Inc., I receive the frantic phone calls and e-mails from people who have discovered on their own the damage household cleaners can do to the color coating or worse the actual integrity of their leather.  In most cases it’s correctable, but sometimes the damage is so severe that the cost of correction exceeds the value of the furniture.  You can learn more about the attributes of leather from our web-site www.ADVLeather.com.

In the Martha Stewart Living article, the author also referred to saddle soap as a possible material to use on upholstery grade leather.  Saddle soap is a generic term that is applied to a number of different products.  However, the same pH issue applies.  In most cases saddle soap has a pH exceeding 10, thus highly alkaline.

Despite the best intentions sometimes advice can be far more dangerous than good.  The lesson here is to be sure that any time you apply a chemistry to leather, identify  its pH so that you are actually helping solve a problem correctly, not executing a “seek and destroy” mission.

The Material Safety Data Sheet (MSDS) of a product usually defines its pH. These can generally be found on-line.