Sunday, September 12, 2010

The pH of Leather - Or, How to Ruin Leather by Following Bad Advice

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

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.

Copyright 2010, Kevin Gillan                

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