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Thread: 1988 C4 Corvette Leather Seat Restoration help

  1. #1
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    Default 1988 C4 Corvette Leather Seat Restoration help

    Hi, Iím new to the forum. I came across this site looking for how to care for Ford King Ranch leather seats and read the sticky about pulling out a stain by spraying cleaner, leaving a tissue on the stain and covering with plastic to draw it out. I was wondering if this process may work on a corvette seat I am restoring.

    Iím helping a friend repair and restore her 1988 Corvette interior. I am starting with the worst seat cushion. I have cleaned it and am at the point now where a few dark stains will not come out. I have used baking soda and water as well as a 2:1 woolite solution to clean the seat. I am looking for some advice on what to do next? Iíve attached pictures of the dirty seat before cleaning and its present condition after cleaning. There are several black areas that are not responding to the cleaner.

    Any help is greatly appreciated!
    Attached Images Attached Images         

  2. #2
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    >>> Hi, I’m new to the forum. I came across this site looking for how to care for Ford King Ranch leather seats and read the sticky about pulling out a stain by spraying cleaner, leaving a tissue on the stain and covering with plastic to draw it out. I was wondering if this process may work on a corvette seat I am restoring.

    Yes, this process is known as “reverse-transfer” when a known stain is worked by penetration, suspension and reverse transfer to an absorbent towel. A stain is easier to remove from the finishes, then from the thickness of the leather crust.


    >>> I’m helping a friend repair and restore her 1988 Corvette interior. I am starting with the worst seat cushion. I have cleaned it and am at the point now where a few dark stains will not come out. I have used baking soda and water as well as a 2:1 woolite solution to clean the seat. I am looking for some advice on what to do next?

    Baking Soda and Woolite denatures or breaks down the leather constituents such as the tanning agent and fatliquor from the leather structure. The leather when dried will become stiff and when flexed will crack easily. You will also notice the leather finishes become tackier too.


    >>> Any help is greatly appreciated!
    Please ask as many questions as you want.
    Or, you prefer me to tell you exactly what to do?
    Or, you want to be educated about the science and logic of leather structure cleaning and conditioning?
    Or, you prefer to have online coaching?

    Name:  rogerIcon.jpg
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    Roger Koh
    Leather, Skin, Hair, Eye & Acne Care System Formulator
    Consultant / Practitioner / Instructor / Coach
    web: www.leatherdoctor.com
    forum: www.leathercleaningrestorationforum.com
    email: [email protected]
    Last edited by Roger Koh; 4 Weeks Ago at 02:44 PM.

  3. #3
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    Roger, thanks for the reply. Please tell me what you recommend I do next to properly treat and restore the seats. Thanks.

  4. #4
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    There are a few phases of restorative work you need done.

    First is to pH neutralize the Baking Soda which in diluted form has a pH value starts from 8.8, it depends on the concentration you have used.

    The woolite has a pH value of 8.0, it will depend on the concentration you used.

    Leather has a pH value of 3 to 5.

    Leather is an amphoteric material.

    The high pH value of both the baking soda and woolite have reversed the protein leather fiber from ionic positive (+ve) to ionic (-ve) negative.

    What this means is that the tanning agents have break hydrogen bond with the leather protein fiber and leached out, turns the leather structure sticky or reverting to rawhide.

    The fatliquor (fat and oil) has also leached out breaking its hydrogen bond with the leather protein fiber and the leather becomes stiff and when flex will crack.

    So, to combine the unknown stain that you wish to removed with “reverse-transfer” technique, the recommended process is as follows:

    Degreaser-2.2 > Acidifier-2.0 + Prep-4.4 > Clean-3.8 > Rinse-3.0 + Hydrator-3.3 > Fatliquor-5.0 > Hydrator-3.3. This combination system is the wet process. And its purpose is to remove stains, pH neutralized, ionic positive (+ve) charged the leather protein fiber to hydrogen bond with the ionic negative (-ve) fatliquor. Here we are dealing with leather integrity as the priority before dealing with appearance.

    Let me know if you have questions about the above recommendation.

  5. #5
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    Quote Originally Posted by Roger Koh View Post
    There are a few phases of restorative work you need done.

    First is to pH neutralize the Baking Soda which in diluted form has a pH value starts from 8.8, it depends on the concentration you have used.


    So, to combine the unknown stain that you wish to removed with ďreverse-transferĒ technique, the recommended process is as follows:

    Degreaser-2.2 > Acidifier-2.0 + Prep-4.4 > Clean-3.8 > Rinse-3.0 + Hydrator-3.3 > Fatliquor-5.0 > Hydrator-3.3. This combination system is the wet process. And its purpose is to remove stains, pH neutralized, ionic positive (+ve) charged the leather protein fiber to hydrogen bond with the ionic negative (-ve) fatliquor. Here we are dealing with leather integrity as the priority before dealing with appearance.

    Let me know if you have questions about the above recommendation.
    Thank you for that knowledge and education. Do you have a kit that includes those products? Could you explain step-by-step how to complete the combination system wet process? If this successfully removes the stain, what is the next process to continue restoring the seat?

  6. #6
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    >>> Do you have a kit that includes those products?
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    https://www.leatherdoctor.com/leathe...-care-kit-af3/

    Leather Doctor Kit-Af3 has the instruction to perform a “restorative cleaning”. For general soil removing and replenishing the original fatliquor (fat and oil).

    See this matrix for other problems . . .
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    Here is a guide for stain identification . . .

    Leather Stain Identification Tips:

    Appearance - Stain identification by appearance will show whether it the characteristic of a spill, rub-on, penetrated or deposited. It may also reveal dye or finishes damages cause by the stain.

    Odor - Stain identification by smell can be very helpful in positive identification. Some of the more common odor may be moldy, smoke, putrid or ammonic from urine.

    Color - Stain identification by color will also give a clue to the staining material. If the stain is red, it could be beverages, nail polish, lipstick, blood, or some other things. Color identification may not necessary be right; with time, a red bloodstain may turn to a stain that is tan to black. The color of the leather may mesmerize or alter the color of the stain.

    Feel of Hand - Stain identification by feel of hand may help determine the stain types. For instance, if it is sticky and red it could be candy, beverages or other things that have sugar in them. If the stain is brittle and stiff, it may be nail polish, shellac or paint. If it smears, it may have grease base to it, such as lipstick.

    Location - Stain identification by location may give a clue as to the makeup of the staining substance. If it is dark at the headrest or the edge of the armrest, it is most likely stain by body oil, grease and perspiration by hand or by head.

    Buildup or Absorbed - A stain may take several appearances. The stain may be lying on top of the leather (buildup) on most pigmented leather or absorbed into the leather on most unfinished, aniline and nubuck leathers. Naturally, it could also be a combination of absorbed and built up. If it has been absorbed, this will be an indication that it was a liquid when it penetrates the leather. It should also alert us that it may have chemically changed the dye of the leather. An example of this would be a perspiration stain that has reacted with the leather dye and changed it in some way. This would occur more likely on dyed absorbent leathers. The perspiration could also have weakened the fibers of the leather. In any event, this leather may show a marked color change in that area after spotting, and possibly after cleaning. Examples of built up stains are paint and some foodstuff, etc. Examples of absorbed stains are beverages, wine, tea, coffee, etc. A combination stain may be lipstick, ink, mustard, etc. it will have part of its staining matter absorbed into the leather and part of it accumulated on the surface. A stain may also be a substance that has wet solvent-soluble and dry solvent-soluble components combined. An example of this would be gravy which contains grease, flour (from plant), and milk (from an animal). Paint type stains are readily detected because of their stiff nature and generally bright colors and they seem to be sitting on top of the leather. When identifying stains always try to a determine whether they are of a protein, cellulose, oil based, or a colloidal make-up nature. Three common types of soiling or stain are solvent-soluble, water-soluble and insoluble. Stains are frequently of a combination nature, and in most instances, there will be no information from the customer regarding the stain especially if they are bought used.


    >>> Could you explain step-by-step how to complete the combination system wet process?

    A restorative wet process with the products from Kit-Af3 is as follows:
    Prep-4.4 > Clean-3.8 > Rinse-3.0 (restorative cleaning) >>> Hydrator-3.3 > Fatliquor-5.0 > Hydrator-3.3.
    To prevent the leather from cracking when dry with insufficient fatliquor (from 14% moisture content when the leather is dry), the leather has to be kept at a total of average 25% moisture content in each process until Fatliquor-5.0, the final Hydrator-3.3 is to clean off any remaining fatliquor from the leather surface.


    >>> If this successfully removes the stain,

    Stains is best positively identified to have the right products, otherwise an intelligent guess may need to
    Determine specialty products to be used. Example, if the Prep-4.4 a general purpose preparatory cleaner may not be as effective if the stain is a grease accumulated stains, thus a second attempt with Degreaser-2.2 > Acidifier-2.0 (degreasing process) >>> Hydrator-3.3 > Fatliquor-5.0 > Hydrator-3.3.
    is recommended.


    >>> what is the next process to continue restoring the seat?

    You have to decide what you want done, after removing the stains and softening and strengthening up the leather structure.

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