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Thread: Vegetable-Tanned (Naked Unfinished) - Fredericia Model 2226 Easy chair “THE SPANISH CHAIR” design by Børge Mogensen – How to removes these unknown stains on these natural hide?

  1. #1
    Join Date
    Sep 2014

    Default Vegetable-Tanned (Naked Unfinished) - Fredericia Model 2226 Easy chair “THE SPANISH CHAIR” design by Børge Mogensen – How to removes these unknown stains on these natural hide?

    Hi Roger,

    I've moved this over to a separate thread. I'm wondering about removal, or at least blending, of the primary ring stain on the attached chair. Unfortunately I do not know the source of the stain but given that there are splatters also on the seat back I have to assume a drink was knocked over. Hard to tell what it is though. Also, regarding the wooden frame, the leather can easily be removed from the frame on this chair for proper cleaning. Attached are images below.

    Kind regards.

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  2. #2
    Join Date
    Feb 2007
    Greater Vancouver, Canada.


    Leather is identified as unfinished vegetable-tanned leathers with this general description:
    Vegetable-tanned leather is tanned using tannin and other ingredients found in vegetable matter, such as tree bark prepared in bark mills, and other similar sources. It is supple and brown in color, with the exact shade depending on the mix of chemicals and the color of the skin. It is the only form of leather suitable for use in leather carving or stamping. Vegetable-tanned leather is not stable in water; it tends to discolor, so if left to soak and then dry it will shrink and become less supple, and harder. In hot water, it will shrink drastically and partly gelatinize, becoming rigid and eventually brittle.

    This Vachetta (V) for unfinished or naked vegetable-tanned leather problem solving guide is used as reference.

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    For unknown stains that rings and browns, the first leather-safe approach is to remove foreign contamination and redistributing the leather constituents back to the overexposure stains by Hydrator-3.3.

    Inspection will decides the next most relevant stain removal process according to the guide as the 1st Phase.

    2nd Phase is the leather rejuvenating process to restore the pH chemistry of the leather and to replenish diminishes fat and oil content with Fatliquor-5.0 to the desired suppleness or up to a 14% fat and oil content when dry.

    3rd Phase is simply sealing any scuffs and protects against friction rubs and sticky soiling with Protector-D, leaving the leather with its natural transpiration characteristic unaltered.

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    Leather Doctor® Kit V4 is a combination of Kit V3 and Kit V5.dr for these common compound grease and browning problems. Kit V4 includes Degreaser-2.2 > Acidifier-2.0 > Hydrator-3.3 system for removing the darkening effect from body stains. Vachetta-2.3 treatment follows for removal of unwanted browning stain or excess suntanned as the second phase. With appearance satisfaction a mandatory Hydrator-3.3 > Fatliquor-5.0 > Hydrator-3.3 leather rejuvenating system follows to restore the leather suppleness from premature cracking. Scuff and abrasion are seal and conceal with Protector-D, besides imparting a non-stick, rub-resistant, non film-forming protection with a draggy-feel in this holistic leather-safe system.

    The degreasing and browning treatment may take the following sequence of processes that matches the degree of soiling severity. Accumulating contaminants from body oil, grease and sweat contact results in unsightly darkening effect. What we see are the mere surfaces soiling but like an iceberg most of the problem are below surface that will require some repeats to bring them all out consecutively. Degreaser-2.2 > Acidifier-2.0 > Hydrator-3.3 leather-safe degreasing system is design to removes both surface and below surface stains. Degreaser-2.2 suspended soiling above surface is removed by towel extraction. Acidifier-2.0 follows as surface rinse with towel extraction. Hydrator-3.3 goes below surface to wick out suspended soiling particulates for towel extraction when dry and Eraser-4 when crispy dry.

    Vachetta is composed of ionic positive (+ve) charged protein fiber that hydrogen bonds with its contributing ionic negative (-ve) charged leather constituents like the tanning agent and fatliquor. The ionic positive (+ve) charged protein fiber is amphoteric, while the ionic negative (-ve) charged leather constituents like the tanning agents and fatliquor are non-amphoteric. The amphoteric protein fiber main composition is easily influences by pH value fluctuation and vachetta being naked unfinished leather is more vulnerable than others. Unsightly stains both from body and accidental liquid contact seems unavoidable, even clean tap water with a pH value of 7 will result in rings and marks. Besides unsightly appearance, pH value above its pH neutral or isoelectric point (pI) does affect its integrity and often manifest as tackiness as the leather denatures or reverting to rawhide in extreme cases.

    From body stains, sweat with traces of urea is the main cause of shifting the protein fiber towards ionic negative (-ve) thus breaking the hydrogen bond and leaches out the tanning agent as discoloration or rings and the fatliquor resulting in stiffness that cracks when flexed. Degreaser-2.2 is design with a pH value below the average pI of leather to effectively suspense the soiling particulates and simultaneously protonate the amphoteric protein fiber ionic more positive (+ve). The ionic strengthening protein fiber is further rinse clean and ionic positive (+ve) charged with Acidifier-2.0 to strengthen the ionic attraction between its other non-amphoteric ionic negative (-ve) leather constituents. This dual duty removes the unwanted soiling particulates and simultaneously pH balance the chemistry integrity of the leather at the same time. In a deep penetrated stain removal process Hydrator-3.3 acts to facilitate colloidal water movement within the inter-fibrillary spaces for wicking foreign soiling particulates to resurface. In rectifying discoloration areas it again facilitates colloidal water movement to redistribute the leather constituents from the surrounding areas back. For optimum deep hydrating process to facilitate colloidal water movement a little moisture should ooze out when the leather is gently pressed between finger and thumb. Each dwelling cycle may take up to 72 hours and cling wrapped to control evaporation is practiced. Advance technique utilizes stretchable paper towel for “reverse transferring” to trap wick through soiling particulates instead of still remaining on the leather surface when the evaporation control is lifted off. Inspection is done when the leather is crispy dry and Eraser-4 worked over for satisfaction and proceeds to browning treatment, otherwise the Degreaser-2.2 > Hydrator-3.3 system is repeated.

    Discoloration or browning of vachetta leathers is associated with alkaline over-exposure other than tannin stains. Excess sun tanning may not be a welcome phenomenon as the tannin agents darkens under sunlight or UV over exposure. Vachetta-2.8 with its lower pH value than the average pI of leather works by oxidation-reduction reaction to reduce the discoloration or browning effect or excess sun tanning to a more even appearance after the leather is left to dry naturally. Inspection is done when the leather is crispy dry and work after Eraser-4, the decision is repeat or proceed to Hydrator-3.3 > Fatliquor-5.0 leather rejuvenating system.

    Hydrator-3.3 when acts as a surface pre-conditioner prior to fatliquor replenishing process, the purpose is to check for surface tension to ensure an even appearance free of blotchiness when dry. For below surface pre-conditioning, it’s to stabilize, pH balance and charge the protein fiber below its iso-electric point (pI) ionic more positive (+ve) to hydrogen bond with the ionic negative (-ve) fatliquor more effectively. Fatliquoring, the last of the original wet tanning process determines the ultimate suppleness of the leather, however as the fatliquor (fat, oil and water) breaks bonds and leaches out, evaporates or diminishes as it ages, it shrinks and stiffen up and when flexes cracks. In a degreasing and or browning treatment process it is mandatory to fatliquor replenishes it up to 14% of moisture content when dry, however as percentages increases so thus color intensity. At each application the water content creates a breathing space as it evaporates, the fat content plumps the leather with fullness from easily collapsing into creases and wrinkles and the fat content lubricates each fibers so that they slide over one another smoothly like millions of inter-connecting hinges. Thus helps to keep the leather at its optimum physical performance and prevents premature ageing. Where appearance is the priority let each application be completely dry, any wick up soiling residue is work with Eraser-4, stretch or flex a little and inspect for satisfaction. Excess color intensity is rectified by application of Vachetta-2.8, let dry, erase, stretch or flex and inspect for satisfaction.

    Vachetta leather is naked without any finishes and Protector-D maintain closest to its original appearance and characteristic.

    Note that the above mentioned products suffix numbers denotes its pH value in this leather-safe holistic approach for degreasing and removing browning stains from vachetta, saddlery and veg-tan leathers.

    This kit comes with reduced weight option to save on shipping thus the 250ml concentrate ratio such as Acidifier-2.0, Hydrator-3.3 and Fatliquor-5.0 has to be cut or filled up with distilled water prior to use.

    Roger Koh
    Leather Care Consultant
    [email protected]

  3. #3
    Join Date
    Feb 2007
    Greater Vancouver, Canada.


    How is the progress.

    Please show some pictures.

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