The Science Behind Leather Protection And Cleaners

There are essentially four different types of Leather that make up most manufactured products. By far the most popular is the type used by sofa and car manufacturers known by many names ‘top grain’, ‘pigmented’, ‘coated’, ‘protected’ or ‘finished’ leather, although we’ll discuss them all in this lesson, the most reported problems are with the Pigmented leather.

Here are the most common problems we hear about…

Jeans Stained My Sofa
Dull patch where I rest my head or sit
Faded in the Sun

And all are the result of the same thing, even though they sound completely different. By the end of this lesson you’ll understand why these occur and how they are all related. Along with the importance how to prevent all three and other related problems.
What Is Finished Leather (also knows as Pigmented, coated and protected)

This type of leather has a top pigmented coat applied such as soft acrylic that contains the colour, and a clear coating on top of that for durability.

These are resins and create a film that bond to the surface of the leather and it’s their to protect the leather underneath from water, stains and fading.

If you drip water or other liquids on top, it will bead and run off or just evaporate, it will not soak into the leather at all due the top coating.

It is possible to have a dull matt finish or a super shiny high gloss finish, this depends entirely on that final clear top coat of resin that’s applied.

Leather: a hide or skin made imputrescible through a process of tanning, complete with original fibrous structures intact.

Modern Leather Production Explained

Leather is animal skin, and most commonly Cow Hide, although sheep, pig and goat are also common. The hide is taken through a process to make it imputrescible, or put another way to prevent it decomposing. In the ‘olden days’ human urine was one of the materials used during the tanning process! Today salt, lime or sodium chloride is used. Together with some chemicals to remove any micro-organisms that would obviously be present in a living tissue.

Often people refer to ‘tanning’ of leather, here is what actually goes on

  1. Pre-tanning – essentially cleaning blood/dirt from the hide.
  2. Hair removal
  3. Pickling
  4. Tanning – one of the most common ways is adding trivalent chromium. At this point in the process the leather is a light blue in colour! There is another more environmentally friendly process that leaves the leather white, which more manufactures are moving to recently, particularly from the automotive industries.
  5. Drying, When alive the hide was around 65% water, after processing the moisture content should be around 12-14 percent.
    At this point we a have what is called a ‘crust’ and it’s something resembling a chemise leather that you’d use to wipe down a car. These are very absorbent, ideal for dyeing and drying cars alike.
  6. Dyeing – the dyes are added to the leather, and it sits in in-between fibres of the leather. They can move around and are not bonded to the leather. You’d usually be able to see the same colour right the way through a cross section, known as struck through. Think of blue jeans here, they are material with blue dye. Leather is similar and in the same way, if you were to ‘wash’ it, you’d lose some of the dye just like with jeans at this point.

The Types of Leather

At this point most leathers are the same, the preceding chemicals do make a difference, but now you can see what happens to create the different types of leather you know of in products ranging from bags, boots to cars seats and sofas.

Aniline leather

A clear surface coating is applied without pigment so you can see the true leather with all the markings and minor imperfections. For that reason, only the full grain most expensive leathers are used.

Nubuck and Suede

Essentially the same, both are buffed or rubbed through specially designed machines. Suede is the flesh side, where as Nubuck is the grain side that forms the ‘visible’ side of the product. Suede has a nap finish produced by the abrasive action on the flesh side where as Nubuck is buffed on the grain side of cow hide, to give a high quality, velvety surface

Semi Aniline leather

Similar to pigmented, but with either much less or no pigment, with a clear top coat for added protection.

Pigmented or Finished LEather

Uses a binding substance to combine a strong pigment to the leather, and has a clear top coat for added protection.

A top coat is added after a pigmented layer that gives a solid consistent colour. this is adding the top coat to make the leather more durable and arguably ruins a lot of the true beauty of aniline leather. Depending on the quality of the leather, the final top clear coat is extra thick to allow embossing of a pattern, which is often what you see on bags etc.

Properties of Finished Leather – What you end up with

Whatever the finish, the leather still needs to ‘breath’ and so any top coat must allow this. Essentially it has ‘holes’ in it at the microscopic level.

Leather itself is very absorbent, this is why it dyes so well and we can have so many colours.

Leather is acidic. On the pH scale (where water is neutral number 7) leather is around 4.5 or 5.

Once dyed and finished, most leathers on seating etc. has a moisture content level of around 25%.

Why Do Jeans Stain My Leather Sofa?

Leather is a very absorbent material, and the dye on your jeans is a very small molecule that isn’t bound to the fibres overly well. Consider when you wash your jeans you see the colour of the water change, that’s the dye. Combined with leather being so absorbent it will happily accept any new moisture or molecules.

Regularly using a good leather conditioner will ‘top up’ the leather, a lot like keeping a sponge full of water. If a sponge is full of water it can’t accept any more. In the same way if your leather is topped up of moisture, it won’t be so eager to accept the blue dye from jeans or anything else either.

If you’ve already got this problem, you’ll want a good leather cleaner or conditioner that contains surfactants. These are developed to bring debris to the surface and allow you to wipe them away, rather than traditional cleaners that will bury the debris further into the leather. See below for our recommendation or here.

Why Does the Sun Fade Leather?

Dyes are not particularly UV tolerant and so unfinished leather is very susceptible to fading. Pigmented leather it much more resilient to UV, it has to be when sitting in a baking car all day.
The problem occurs somewhere between the two types, essentially the Ultra Violet rays of the sun break down the dyes causing fading. The best way to recover from this is to ‘top up’ with dye. Lesson 3 will go into this next time.

Why Does Leather Crack?

Upholstery grade leather has a moisture content of around 25%. As the sun dries the leather over time, it will shrink slightly and so crack it.

Also it will become dry and ‘less supple’ or more stiff. If the moisture content becomes too low the leather disintegrates or becomes so brittle that upon touching, it disintegrates.

This reduction in moisture also takes away some of the oils that are naturally part of leather.

A good leather conditioner will replace the moisture and the natural oils so preventing this problem.

If the leather has already cracked somewhat, then watch out for Lesson 3 next week as we’ll go into how to resolve this, and the scratches from cats and dogs!

Why are there Dull Patches On My Leather?

These are usually due to excessive oils in that part of the leather. Let me explain. Oils are a natural part of leather, and as we know, leather is very absorbent. Oils are constantly secreted from human and animal skin too, and over time the appearance of those oils is shown in dull patches on lighter coloured leather. You won’t see this on very dark brown or black leather. 

By using a good conditioner you’ll be replacing the natural oils of the leather, and in much the same way as a sponge full of water won’t accept any more water, your leather will be the same, thus preventing this problem.

If you’ve already got this problem, don’t worry, Lesson 3 next week I will show you how to resolve this. But you can’t clean them off, they are in the leather, it would be like trying to clean a tattoo from your skin.

Choosing a Leather Conditioner

Ok, by now you should realise that choosing a very good quality leather conditioner will save your leather and make it last much longer.

A good leather conditioner will prevent cracking
A good leather conditioner will prevent dyes from transferring into your leather (the blue jeans effect)
A good leather conditioner will help prevent other oils entering the leather

So now you know, you need a good leather cleaner and conditioner.

Most leather conditioners are from the Auto Industry. They will certainly add a shine to leather… initially. The mostly contain silicones (like standard household furniture polish), but over time will significantly reduce the lifespan of your leather. Going from what I’ve discussed about how leather is made above, you can see that leather has many oils in it, no mention of silicons! So it makes a great deal of sense that any conditioner you buy should have natural oils (fat liquors) in it to replace what is lost through daily use.

Using standard household products with the incorrect pH level will stiffen and reduce the longevity of the leather, as you now know, leather is around a 4-5 pH, household cleaners are much higher (they are alkaline) and so using them causes a chemical reaction to occur in your leather, not good for the long term life of your leather.

Please take care when choosing the right products, there is a lot of misinformation online about how to treat leather, but knowing how it’s made you can see our leather balms contain natural oils to feed, and surfactants to remove the grime.

"The Simplest and Best Leather Cleaner and Conditioner We've Ever Used"

The simplest and best leather cleaner and conditioner we’ve found is an all in one. I understand anything complicated isn’t going to get done regularly, and we’ve tested many separates and combined. This works great for all the problems discussed here. Like anything you should spot test an inconspicuous area first.

For black leather, use the black cleaner and conditioner, it adds a little dye back too!
For dark to medium brown leather, use the brown cleaner and conditioner, it adds a little dye back.
For all others you’ll want our excellent neutral cleaner and conditioner.

If you’ve Nubuck or Suede, you’ll want the Universal Cleaner and then for Suede a stiff brush here.

I hope you’ve found this lesson useful. If you’ve any questions for comments then please do contact me. Or comment below.