88 We visit the experts at Gliptone to learn about leather and to see how to make an invisible repair using DIY products.

Gliptone and Leather Master, available from Staingard, are two of the most famous names when it comes to leather care, and in the UK both are in the same family. We visited their Cheshire premises where experts Paul Aiston, Tom Aiston and John Severn explained all about leather, then showed us how to make an invisible repair in a modern example.

Before we get going in earnest, we should make clear that this one feature is not going to make you an expert leather repairer – the subject is simply too vast and the number of repair types too varied for that to be possible. Instead, what we hope to achieve is to give you a greater understanding of the product, and also to demonstrate the kind of results you could achieve when making a repair using DIY materials. So after a condensed history of leather and of the various types available, we will show how to repair a small hole such as a cigarette burn. For this we will use a piece of modern leather, which tends to have a protective polyurethane layer on top as we shall shortly see. Older cars up until the mid-1970s are likely to have untreated leather and a repair on these will vary in detail, though the basics will be the same. However, we are not going all modern on you, because owners of many classic sports cars from the likes of MG and Triumph will have fitted brand new leather covers to their seats, either because the original fabric covers have worn beyond repair or simply as part of a general upgrade.

We should also sound a note of caution when assuming that the original leather you may have in your classic is still to original spec. Our project Nissan Figaro, for example, was fitted with leather from new, but the seats had always felt hard and plasticky to us. John Severn examined them while we were in Cheshire, and concluded that they had been heavily pigmented by a subsequent owner – effectively painted over. This top layer was so thick that it was reducing the flexibility of the leather. It was also cracking, and many of the problems we could see were in the pigment rather than in the leather itself.

In the Figaro's case, John recommended stripping the applied coating off the leather as a first step and then assessing what needs to be done to repair any remaining damage, revive the leather and protect it. Everything you would need to do this – both products and advice – are available from gliptoneeurope.com, but John estimated that having both seats done professionally by them would cost around £350-£500, something of a bargain.

LEATHER FOR BEGINNERS

We'll get to an actual repair in a moment, but first let's just whip through the subject of leather in general as explained by Paul and Tom. (And even though we are going to start with the cow, don't worry because this really is just a brief overview of a very detailed subject!) So, when the skin is stripped off that cow, you get the hide. At this stage called a hair- on-hide, you could use that for an odd effect, and if you go to places like Texas then you will indeed find furniture made out of it. For us though, the next stage in the process is a hide minus its hair that has been stabilised and tanned.

Tanning is the process of converting animal skin into leather by soaking it in a liquid containing tannic acid. In past centuries the use of human urine was quite common for tanning, and they would send barges of the stuff from big cities like London to tanneries in places such as Northampton. That's where the expression 'He hasn't got a pot to piss in' comes from, meaning somebody is so impoverished that they don't even have a pot so they can collect and sell their own urine. Nice!

Chromium salts were widely used to tan hides as they were cheap and effective. The chromium gave the leather a distinctive coulour that gave rise to the name for the next stage – Wet Blue. However, chromates are not great for the environment and will still be in the leather when a car is scrapped because they have a long half-life. In 2000 a regulation came into force in the EU that 95% of abandoned vehicles must be recycled by 2015, so the automotive leather industry is now using more eco-friendly ways of tanning, and instead of Wet Blue is now turning to what is known as Wet White, which is tanned using a combination of glutaraldehydes, zirconium and other vegetable tannins. Around 30% of the leather currently used by the automotive industry is Wet

White, while most classic car leather was vegetable tanned giving the true smell of leather. Connolly leather was tanned using this method, and is famous for being used in very high end vehicles.

A good hide can be anything up to 10mm thick, so it is then usually split in half to give effectively twice as much material. Sometimes it is split three times, but that leaves all but the first layer very thin and weak. The outer layer is known as Top Grain and this is what we call leather, while the back layer is referred to as the ‘split hide’ and has a finish more like suede. You can finish the outer surface of the ‘split’ to look like leather, pressing it flat, marking in a grain pattern and covering it with colour and a protective polyethylene coating, but this is not as strong, durable or supple as the real thing and you are not allowed to call it pure leather – instead it is known as Bicast (or Bycast) leather.

At the Wet Blue stage, the tanner will have to decide how good the leather is. Things like barbed wire scratches or insect bites will leave marks that detract from its appearance and suitability for use in cars, although there are times when it is fashionable in furniture and clothing to retain and celebrate marks such as natural scarring and branding.

Top Grain will generally need to be coloured. If this is done using a soluble dye, then the colour will go right through the material and leave the surface in its natural state. This is called Aniline leather. Aniline is uncoated, so it is soft and warm

to the touch because it will take ambient temperature, but it is more easily marked and so generally unsuitable for use in cars.

More typically, a car manufacturer who wants to create the luxurious feel of Aniline leather will use a Nappa leather. Traditionally that comes from a sheep or goat, which is softer than cow leather and very thin but strong. This softness is where we get the expression 'treated with kid gloves' from, meaning to treat very gently. (As an aside, there is also an animal called a Chamois which is a cross between a goat and a sheep. This is an extremely hairy animal, which is why chamois leather is so absorbent because it has so many hair follicles.) The problem with Nappa is that because it is so soft, it can stretch where you sit and not return fully to its original shape. This problem tends not to be so bad in a car because the seat foam is generally quite firm and supportive, but it can be a bigger problem with household furniture. Nappa is not a protected name though, so these days it is sometimes applied to cow hide that has been cut very thinly, and although that will be soft, it won't be nearly as strong.

Aniline only represents about 5% of the leather produced. The next step for use in cars these days is a Pigmented hide. This has a pigment layer applied on top of the leather to provide uniform colour and appearance, followed by a protective polyurethane layer to enhance its durability and wearing characteristics. This layer also helps protect the leather from spills and scratches, making it easier to maintain.

If a hide has had lots of imperfections, then it can be sanded and sprayed with a self-levelling compound to correct them – this is called a Corrected Pigmented hide. Of course we are now coming down in price, but in all cases the thickness of the added layers cannot be more than 0.15mm if it is still to be called real leather according to the British Standards.

CARE AND MAINTENANCE

Older hides used originally in many classics would have been plain dyed hides without any protective polyurethane layer. That is why they needed feeding on a regular basis to keep them soft and supple. On more modern leathers you don't need to do this because the manufacturers put fat liquors into the leather (much like a moisturiser we would put on our skin) before the pigment and the PU layer which then lock that moisture in. This started coming in around 25 or 30 years ago so most classics with original leather will still benefit from regular

feeding, but if you have fitted new leather covers then it probably won't be necessary.

Leather that has been allowed to dry out becomes brittle and easily torn, much like a dried out leaf. So on an old seat that requires repair, you would first put on a conditioner, then leave it for a week or so to really soak in. Then you would polish up the surface to remove any oils, before moving on to repairing any damage once it is soft and supple once more. After the repairs, you can look to colouring.

If leather is cracked, normally the edges of the crack will be raised. You have to flatten those edges down before repairing, but go easy because you don't want to do any more sanding than necessary. You can then apply a product such as Gliptone Aquafil, which is a flexible, water-based, putty-type filler that can be used on leather and vinyl. This can be tinted to match the rest of the leather, but the real colour matching comes afterwards.

Splits in leather can be repaired, too. Basically you have to glue a cloth patch on the back of the leather which strengthens the split, and then you can treat it as a crack. You can also replace a single piece of leather, but you would really want to find an old hide from which to take a piece for this, and look at the grain rather than the colour – specialists such as Gliptone can match any colour in the world, but a different grain will always look wrong. ( We will come back to grain matching overleaf when we show a repair.)

'Cars can be repaired in-house, or DIY kits can be sent out,' explained Paul Aiston. 'The products are very easy to use and as long as you follow our FAQs, you should be able to achieve good results as a DIY enthusiast. The most common mistakes people make are poor prep, and overapplication of the pigment. Much like painting a car, the pigmenting is the easy and fun bit and all the hard work should have gone into the prep.

' While a conditioner will be vital on old leather, modern leather care from about the mid-1990s focuses more on caring for the finish rather than the actual leather. Gliptone's conditioning cream, for example, will be eagerly absorbed by an Aniline leather, but while a modern leather will absorb some, it will only take a very little. Drying out is a major concern for older seats, but the enemies of more modern leather in a car are abrasion, sweat from hands and bums and heads, and dye transfer from clothes. Jeans provide both dye transfer and abrasion, but if you can make leather slightly more slippery, you can help to minimise these problems. That's why modern leathers need a surface protectant rather than a conditioner.

‘ We do steering wheel restoration kits too. They contain everything you are likely to need for vinyl or leather, either as a standard colour or you can specify a bespoke colour. The fact that our repair products can be used for both vinyl and leather is important because many manufacturers will use vinyl around the back and sides of a seat to save money, and reserve the leather only for the facings. A quick test is that if the leather is soft and you press it with your finger, it will crinkle around the pressure point. Do the same on vinyl and it won't crinkle, just dip.'

The enemies of more modern leather in a car are abrasion, sweat from hands and bums and heads, and dye transfer from clothes

MAKING A REPAIR

Finally, John Severn demonstrated how to repair a small hole in leather, the kind that could be caused by a cigarette burn or a nick from catching the surface with a sharp object such as a rivet on your jeans or a pet's claw. For this we used an offcut of leather, but the steps show exactly the same process that would need to be followed if the hide was still on a seat.

ABOVE: The seats in our Nissan Figaro felt hard and unyielding rather than soft and supple. This tell-tale trace of grey on the piping shows that they have been painted.

ABOVE: To find a piece of original leather for colour and grain matching, a good tip from John is to look under the headrest. LEFT: These cracks were actually in the paint rather than the leather itself. Stripping off the top coats would be the first step in renovation.

ABOVE: Still recognisably a cow, not many people outside of Texas would consider this a suitable covering for furniture or car seats.

LEFT: Aniline leather looks more conventional, but it is unprotected and will absorb moisture – as the water staining in one corner of this sample shows.

Pigmented and Corrected Pigment hides feel natural because the top layers must be less than 0.15mm thick for it to be classed as real leather.

ABOVE: this back seat from a 1930s Bentley is covered in Connolly Luxor leather. It is a very absorbent, and feeding keeps it supple. LEFT: The Luxor has two colours applied – a lighter one first, and then a dark one which is wiped back off so that it stays only in the pockets of the grain. That gives the two-tone effect – it is not dirt!

ABOVE: Liquid Leather's repair kit of cloth, tools, glue and filler costs £25.25. Add some Scuffmaster pigment and you can effect excellent repairs that will be virtually invisible.

The Scuff Master steering wheel repair kit contains everything you need to create an invisible repair – except the necessary patience!

ABOVE: Bycast leather is the inside layer of a hide that has been processed and treated to look like Top Grain, but it is weaker, looks plasticky and is more likely to crack.

ABOVE: Before cleaning or treating a seat, use a dry brush to clean out as much dirt as you can from the seams and crevices, otherwise you will end up dragging this across the leather and abrading it.

Cleaners come in different strengths. Start with a gentle one, and use a brush to work it into the lower parts of the grain as a sponge will skate across the surface.

ABOVE: Scuff Master is designed for small and localised touch- ups, but this test seat shows that you can effect big changes to leather with pigment.

8 At this point you can still see the repair because of the colour. So John then dabs a little pigment on, dries this off and sees how close it is. He repeats this step as necessary. This is where the graining comes into its own as it really makes the repair disappear.

10 Once the sealant is dry, the finished repair is truly all but invisible. John adds that as the repair is also more flexible than the leather, it will not crack or break in use.

9 Finally he sprays on a little lacquer, heats it to dry and checks the finish – you can get matte or gloss sprays. Again, go for lots of thin coats until the desired effect is achieved.

1 The first step in our repair was to put a circle of Liquid Leather Graining Mat onto the surface of the leather, let it dry, then peel it off to get a reverse pattern of the grain.

5 A contact structural adhesive is then used to glue the calico patch to the back of the leather. The glue is pushed through the hole and spread with a palette knife.

7 When the repair is level with the surface of the surrounding leather, before the filler dries he presses the grain mould from step 1 onto it to transfer the pattern.

6 John then used Heat Cure filler on top of the calico backing to raise the repair up to the level of the surrounding leather. This is done in a number of thin layers.

2 We need to fix a patch of calico behind the damage. John puts a dot in the middle of this patch, otherwise once it is behind the leather he won't know where the edges are.

4 Popping a pin through the centre dot to hold it in place, he then works it out under the leather. It is awkward when it is so small, but you can open up the hole if necessary.

3 He rolls the patch like a cigar one way, then turns it the other way and rolls the other half. After folding it in again on itself, he pokes the first half through the leather.