LEATHER SOFA CONDITIONING PROCEDURE

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Highly worn leather will show its age over time. Routine cleaning and protection with ‘Leather Cleaner’ and ‘Leather Protector’ help prevent many undesirable characteristics but cracks, scratches, cuts, fading and abraded areas sometimes become evident anyway

The complete finishing of furniture is advisable in these situations:

· Widespread damage

· Where dirt has penetrated to a degree that means cleaning necessitates removal of the previous finishing

· When the original finishing of the article appears to be worn after years of usage

What is finishing?

There are 3 types of finishing

  1. A finishing created using transparent dyes (anilines), especially for high quality leather with no natural markings. This gives a very natural, transparent finishing but leaves the leather vulnerable to staining so should only be used on leather kept in protected areas (e.g: Luxurious living rooms.) It is not recommended for car interiors due to its low fade resistance to solar radiation.
  2. A finishing that uses an initial layer of pigments onto which a transparent layer (top coat) is applied. The latter protects the leather making it resistant to external damage.
  3. Nubuck has a very pleasant, soft, natural feel but is extremely delicate. In fact, it is not recommended for use on leather car interiors and is now rarely used on sofas, replaced by microfiber fabrics, that are easier to care for.

The aniline and pigmented finishes can be partially removed and then renewed with a pigmented finishing that returns the leather to its original condition with a brand new look.

Fenice supplies the same technologically advanced, highly performing products for the restoration of leather finishing, as the tanneries, to ensure that the renewed leather gives maximum softness and strength.

To renew the finishing of highly worn automotive leather the following preparation and finishing procedure is recommended:

  • Clean thoroughly
  • Fill any cracks
  • Remove the final layer of finishing which may have absorbed dirt, grease and stains
  • Spray a coat of a primer or adhesion promoter to form a strong bond between the leather and the new finishing
  • Spray a colored layer to hide any defects or residual stains, leaving the leather with a brand new look
  • Spray a top coat to create a transparent barrier against external damage and to give the leather its final look and feel

 

Leather Renovation

Adhesion

When is good adhesion necessary? 

When working on a leather that has already been finished monitor adhesion carefully to ensure that products adhere well to the previous finishing.

Older finished leather can present various problems of adhesion due to dirt, grease or poor finishing.

Check adhesion after the application of each product, especially after the first coat and after having cleaned the leather.

How can good adhesion be obtained?

By cleaning and degreasing the leather prior to any spraying application and only using specifically designed products for leather.

By diluting 1 coat of the water-based ‘Adhesion Promoter’ and crosslinking it will normally be sufficient to ensure good results.

‘Extra Adhesion’ is a highly performing, ready to be sprayed product which is a quicker alternative if a solvent based product can be used. Finally, by mixing ‘Color Bonder’ with ‘HCC’ or ‘PBC’ colors to grant exceptional adhesion on even the most problematic surfaces.


How can adhesion be tested?

Leave the finished leather for 4 hours. Apply wide, transparent adhesive tape to the leather surface. Remove it quickly to see if any color has been removed. If so, adhesion is poor and the leather will delaminate easily.

How can leather defects be corrected during the finishing process?

Leather finishing can be done on full grain leather (where the natural surface of the leather can be seen like human skin) or on buffed leather. Buffed leather is obtained by sanding full grain leather with a specially designed machine using sandpaper of the appropriate thickness according to the result required i.e. 180 for low quality leather, 600 for higher quality leather.

This operation is done on leather with many defects, therefore buffed leather has a lower value. Buffing helps to hide defects.

To improve leather quality a stucco (or paste) called ‘Mender’ is sometimes applied by spatula to fill deep cracks and other defects. When dry, the leather is buffed, then finished. The above procedure is done in the tanneries and Fenice uses the same process during leather re-finishing.

The type of sanding performed on a leather creates an additional classification of leather:

  • FULL GRAIN: non sanded;
  • CORRECTED: (snuffed) sanded with fine sandpaper. The top grain is still partially on the leather;
  • BUFFED: sanded so that the top grain is fully removed.

A pattern similar to the original grain is then recreated by embossing the leather.

The role of the Eco - Crosslinker

Why use crosslinkers?

‘Crosslinking’ chemicals are added to either ‘water’ or ‘solvent’ borne top coats to improve the performance of fastness including rub resistance, wet and/or abrasion resistance of finished leather.


What are crosslinkers?
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Crosslinkers are complex organic molecules which create chemical links between the molecular chains of the polymers in the topcoat film deposited on the leather. This chemical reaction can be seen through a microscope. This diagram shows an example of Fenice’s ‘Adhesion Promoter’ without any crosslinkers: An enlarged version of Fenice’s ‘Adhesion Promoter’ without any crosslinkers. However, if crosslinkers are added to Fenice’s products before spraying, this forms ‘bridges’ that anchor the product molecules together and to the leather, greatly increasing its rub resistance properties.

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To be specific, this reaction creates a tri-dimensional structure that dramatically increases the top coat’s mechanical properties such as surface hardness, toughness, flex resistance. This crosslinking reaction also reduces and even removes the presence of water sensitive hydrophilic functional groups in the polymeric structure resulting in greater water resistance and improved wet rub fastness.

Why must a mixture containing crosslinkers be used within 8 hours?

Crosslinkers are made of reactive molecules, dissolved in inert solvents that start to react as soon as they are added to the topcoat. Better results are achieved more quickly but the creation of these ‘bridges’ starts a reaction which continues, increasing the product viscosity meaning that it becomes unusable within a short time, usually 8 hours.

How are crosslinkers be added to the mixture? 

The dosage and the way the crosslinker is added to the fixing agent needs to be done very carefully: Add a crosslinker slowly, while stirring, to avoid it reacting too quickly with the topcoat.

Fenice recommends ‘Eco-Crosslinker’ - an effective, easy-to-use crosslinker which is particularly suitable for crosslinking with water-based topcoats.

Fenice recommends following these simple rules:

- Add ‘Eco-Crosslinker’ to the topcoat in a ratio of 7-8% of the total weight of the final mixture just before use.

- Add ‘Eco-Crosslinker’ slowly whilst stirring to ensure the crosslinker is perfectly dispersed in the fixing agent.


How long does it take for the crosslinking process to complete?

Once the mixture of the topcoat and crosslinker has been applied and left to dry, the crosslinking action will gradually increase general resistance (particularly wet and rub resistance). The whole process is normally completed within 48-72 hours.


How should leathers be dried after the application of a crosslinked mixture?

The leather must be dried thoroughly after the application of the topcoat because the crosslinker within the applied film is sensitive to humidity. If the leather is dried well with a hairdryer after fixing, all the crosslinker contributes to improving the physical characteristics of the leather. However, if left to dry naturally, the performance of the leather will be slightly reduced because part of the crosslinker will have been neutralized by the humidity in the air. The positive aspect is that the leather will perform better than any treated with a fixing agent without crosslinkers.

What precautions should be when using crosslinkers?
There are some important safety precautions which should always be followed when using all chemical crosslinkers.

  • Avoid direct contact with skin.
  • Use impermeable rubber gloves.
  • Do not inhale any vapors.
  • Only use the product in well-ventilated areas.



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