Leather Types and Restoration TechniquesPosted on January 15th, 2018
The most attractive and natural leathers due to their soft natural feel and appearance. These are leathers which have been aniline dyed through in a vat and have no sealant coating. They are the most expensive leathers to produce because only the very best selection of hides can be used to produce full aniline leathers. Full aniline dyed leathers are very absorbent and thus can be stained easily through spillages or contact with oils/greases. They are also extremely susceptible to fading and sun damage.
Stains are almost impossible to remove without damaging the leather and thus in most cases restoration will involve dyeing the leather slightly darker to blend blemishes. Colour can be restored to a close match by using blends of dyes and cellulose based sealants to create a more uniform and non patchy finish. The result is that the leather would now be classed as semi-aniline leather and will be slightly less absorbent and delicate.
Pull Up Aniline
This is a type of aniline leather that has an extra top treatment of oil and/or wax effects. These Pull Up leathers are designed to become “distressed” looking through time and use. Its properties are similar to full aniline but in places of heavy use, the oils will be pushed away leaving lighter areas – particularly on the seating areas. It will also scratch easily.
If the leather is not too worn or faded the “Pull up” nature of the leather can be restored using a blend of intensive conditioners and waxes. When colour fading or stains are present restoration is likely to involve the same techniques as Aniline Leather.
Semi Aniline Leather
Semi-Aniline leathers have been both dyed through and have a thin sealant layer on the surface. They offer a combination of the softness and feel of full aniline leather with the protective benefits of a surface finish. By dyeing the leather through before the final thin top coating is applied, a very even colouration is achieved with only a thin layer of finish which creates a rich depth of colour. The leather remains softer because it is not necessary to apply a thick sealant coating.
Issues occur with semi aniline as soon as the top sealant coat begins to wear away, the underlying leather is the same as aniline and thus very absorbent and susceptible to fading. Staining and sun damage can occur. As the leather is dyed this normally means that the leather will be restored by using dye and cellulose sealant combinations both to restore colour and the top coat finish.
The leather may be buffed (corrected) to reduce heavy natural scarring and blemishes in the hides. It is then coloured with a polyurethane coating containing opaque pigments and embossed with a grain pattern to ensure a uniformity of colour and resistance to fading.
Issues with pigmented leather are normally caused by damage to the pigmented polyurethane coating. This can be through standard wear and tear, unorthodox cleaning methods, pet damage, or prolonged oil/grease contact.
Restoration for pigmented leather starts with good preparation, usually involving deep cleaning, degreasing and some stripping of the original finish. The leather surface can then be made stronger and more adhesive with binders and adhesion promoters. A new pigmented polyurethane finish formulated to match the original as close as possible can then be applied to the leather, before a sealant layer protects all and creates the correct gloss level. In this way most damage to pigmented leather can be made almost as good as new.
Nubuck or Brushed Leather
This is an aniline leather which has been brushed to break the surface of the leather, leaving it feeling velvety soft. Nubuck is incredibly absorbent and susceptible to staining and sun fading. It should always be treated with a stain repellent as restoration is very difficult without changing the nature and feel of the leather.
This is a manmade product using the leftovers from standard leather production. A hide of leather is split with the top surface being used for any of the above leathers whilst the bottom “split” is kept aside to be made into bi-cast. The split is coated in a glue and the a thick polyurethane leather look coating is rolled on.
The most common problem with bi-cast is delaminating. This can be caused by heat, but also as the split and polyurethane coating stretch at different rates. Once delamination begins it is almost impossible to stop or repair it effectively. We generally do not recommend any attempt at restoration and would prefer that this type of leather was produced in the first place!