How Is Leather Made?

Origins of Leather

Animal Sources Used for Leather

Most leather used in furniture comes from cowhide due to its size, strength, and availability. However, several other animals are used to create different types of leather:

Buffalo: Thicker and more rugged, often used in rustic furniture

Goat: Softer and more pliable, often found in smaller decorative pieces

Sheep: Lightweight and smooth, though less durable

Pig: Recognisable by its porous texture, used in lower-grade furniture

Each hide type has unique properties that impact the final feel, look, and use-case of the furniture

Sustainability in Leather Sourcing

Leather is a by-product of the meat and dairy industries. Without leather production, these hides would end up as waste. Modern tanneries are increasingly focusing on sustainable practices, reducing chemical usage, and investing in eco-friendly processing methods to lower the environmental impact.

Ethical Considerations in Leather Production

While leather is natural, the ethics behind its production vary. Ethical leather sourcing includes:

• Using hides from animals already processed for food
• Avoiding exotic or endangered species
• Supporting tanneries that follow humane treatment and environmental guidelines

When choosing leather furniture, always inquire about the origin and ethics behind the material. Responsible production supports both environmental sustainability and animal welfare.

The Raw Hide Stage

What Is Raw Hide?

Raw hide is the untreated skin of an animal, typically from cows, that is delivered to tanneries for leather production. At this stage, the hide still contains proteins, fats, blood, and hair, and will quickly decay if not preserved.

Hide Selection Process

The quality of finished leather begins with the selection of the right hide. Tanneries inspect for:

• Scars and Branding Marks: Lower aesthetic appeal
• Parasite Damage or Tick Bites: Reduces durability
• Thickness and Texture: Influences the type of furniture it can be used for

Only the best hides are chosen for full-grain or top-grain leather furniture.

Curing and Preservation

Why Hides Must Be Preserved Quickly

After removal from the animal, a hide begins to decompose within hours due to moisture and bacteria. Prompt preservation is crucial to:

• Prevent bacterial decay
• Retain the collagen structure
• Maintain leather quality during transport

Salting vs. Drying Methods

Curing methods include:

• Salting: Common and effective; hides are heavily salted to draw out moisture and inhibit microbial growth
• Drying: Air-dried hides are lighter for shipping but prone to brittleness
• Brining: Immersion in saturated saltwater; faster but requires more clean up at the tannery

The method chosen affects how easily the hide can be rehydrated later in the process.

Impact of Poor Curing on Leather Quality

Poorly cured hides may show:

• Rotting or foul odours.
• Weakened structure and elasticity
• Irregularities in dye absorption
• Reduced yield in usable area

At Leather Cleaning Brisbane, we’ve seen many upholstery pieces degrade prematurely due to inferior leather quality that started at this stage.

Soaking and Rehydration

Purpose of Soaking Hides

Upon arrival at the tannery, hides are stiff and dry. Soaking does the following:

• Rehydrates the hide to its natural pliable state
• Removes salt and dirt residues
• Prepares it for the liming stage

This soaking typically lasts 6–48 hours depending on the hide type and curing method used.

Cleaning Impurities and Dirt

During soaking, hides are also washed to eliminate:

• Blood
• Fats and proteins
• Dirt from transport

Tanneries may use rotating drums, paddle vats, or soak pits to manage large volumes of hides efficiently.

Rehydration Techniques

Rehydration involves gradually restoring moisture without over-saturating. Modern tanneries use softened or recycled water to ensure environmental sustainability. Temperature control is crucial, as overheating can cause hide degradation.

Liming Process

Removing Hair and Epidermis

The liming process involves soaking hides in a solution of lime (calcium hydroxide) and sodium sulphide. This:

• Loosens the hair and upper skin layers
• Opens up the hide’s fibre structure
• Begins collagen fibre swelling to aid further chemical penetration
• Hair is mechanically scraped off once loosened

Swelling and Splitting of Fibres

Liming causes the hide to swell, making it easier to split into layers. This also separates the grain layer (used for high-quality leather) from the lower split layers (used for suede or bonded leather).

Use of Lime and Chemicals

While lime is the main agent, other chemicals like enzymes or wetting agents may be added to improve efficiency and minimise environmental impact. Wastewater from this process must be carefully treated due to high alkalinity and sulphide content.

Fleshing the Hide

What Is Fleshing?

Fleshing removes excess fat, meat, and connective tissue from the hide’s inner side. This step ensures a smooth, even thickness and improves dye penetration later on.

Machines Used in Fleshing

Large rollers with dull blades are used to strip away unwanted tissue. Manual fleshing is rare today due to time and labour constraints. Industrial machines can process hundreds of hides daily with precision.

Role in Final Leather Thickness

Fleshing determines the base thickness of the leather. Furniture-grade leather often ranges from 0.9 mm to 1.4 mm thick, depending on application and desired softness.

Deliming and Bating

Neutralising Alkalinity

After liming, the hide is highly alkaline and swollen, which makes it too stiff for quality leather production. Deliming uses mild acids, such as ammonium salts or carbon dioxide solutions, to gently lower the pH of the hide. This brings it closer to the acidic conditions needed for effective tanning.

The goal is to:

• Remove residual lime
• Deswell the fibres
• Stabilise the hide structure for bating

Enzymatic Softening

Bating follows deliming and involves treating hides with natural enzymes. These enzymes digest any remaining non-leather-forming proteins and help break down rough areas within the hide structure. This process results in:

• Improved softness and flexibility
• Better grain tightness and smoothness
• Enhanced dye and chemical penetration

The bating stage is critical for achieving the supple feel found in premium leather upholstery.

Preparing for Tanning

The hide is now clean, soft, and evenly swollen. The structural fibres are relaxed and receptive to tanning agents. Any mistakes at this stage can lead to hard or brittle leather later, especially noticeable in furniture subjected to regular wear.

The Role of Acids and Salt

Pickling The Leather

Pickling involves immersing the hide in a bath of salt and acid (usually sulfuric or formic acid). This step:

• Lowers the pH to around 3–4
• Prepares the collagen fibres for efficient absorption of tanning agents
• Prevents bacterial growth during the transition to tanning

Salt acts as a stabiliser to reduce the hide’s water absorption, avoiding over-swelling or damage.

Preparing for Tanning Process

The acidic environment is crucial for chrome tanning, which is the most common method used for leather upholstery. Pickling:

Opens up fibre spaces

Ensures even chemical penetration

Minimises grain damage

Pickling and pH Balance

Tanneries monitor the pickling bath pH meticulously. If the pH is too high, tanning will be incomplete. Too low, and the hide structure can collapse. A properly pickled hide has a soft, flaccid texture and a slight acidic odour.

The Transformation

Tanning The Leather

Tanning is the most critical transformation in the leather-making process — it is what converts raw, perishable animal hide into durable, long-lasting leather suitable for use in furniture. For leather upholstery, tanning must not only preserve the hide but also create leather that is soft, pliable, colour-consistent, breathable, and resistant to stretching, cracking, or sagging over time.

Why Tanning Is Vital for Upholstery-Grade Leather

Upholstery leather must meet specific performance criteria that are very different from footwear or clothing leather. It needs to:

• Withstand tensile stress from being stretched across frames

• Endure abrasion and friction from daily use

• Retain colour and finish under sunlight and indoor lighting

• Remain soft and comfortable to the touch for many years

All of these properties are established during the tanning stage, making it the most influential process in determining the longevity and comfort of leather furniture.

Common Tanning Methods for Upholstery Leather

1. Chrome Tanning (Chromium III Sulfate-Based)

Most commonly used tanning method for leather furniture (used in ~90% of upholstery-grade hides globally).

Process Overview:

• Hides are soaked in a chromium salt solution (usually chromium(III) sulfate)

• The chromium ions crosslink with the collagen fibres in the hide

• This stabilises the fibres, making the leather soft, supple, and heat- and water-resistant

Why It’s Preferred for Furniture:

• Soft and flexible — ideal for wrapping over cushioning or furniture curves

• Consistent dye absorption — excellent for full-colour upholstery

• High resistance to moisture, stains, and wear

• Allows for a range of finishes (matte, gloss, pigmented, etc.)

Drawbacks:

• Contains metals, making it less eco-friendly unless properly managed

• Not biodegradable, although many modern tanneries treat chrome waste safely

2. Vegetable Tanning (Plant-Based Tannins)

Rarely used for full-size leather furniture but still relevant in artisan, custom, or eco-conscious settings.

Process Overview:

• Uses tannins extracted from tree bark (e.g., oak, chestnut, mimosa)

• Takes several weeks of soaking hides in pits or drums

• Produces a firmer, denser leather

Why It’s Less Common in Upholstery:

• Results in stiffer leather, more suited to luggage, belts, or saddles

• Limited stretchability makes it harder to upholster around curves or corners

• Darkens and stains easily

Where It May Be Used:

• Accent furniture

• Decorative panels

• Artisanal or bespoke furniture where a raw, rustic appearance is desired

3. Semi-Vegetable (Combination) Tanning

Hybrid approach, combining the speed of chrome tanning with the body and feel of vegetable tanning.

Why It’s Used in Upholstery:

• Offers added firmness to chrome leather without sacrificing flexibility

• Creates more body for structured cushions or traditional furniture

• Improved environmental profile compared to full chrome tanning

Combination-tanned leather is often used in premium, European-style furniture, where both structure and comfort are required.

4. Synthetic (Aldehyde or Glutaraldehyde) Tanning – “Chrome-Free Leather”

This method is increasingly used for eco-conscious furniture brands looking to eliminate heavy metals.

Process Overview:

• Uses aldehyde-based chemicals (e.g., glutaraldehyde or oxazolidine)

• Produces white or pale wet leather (wet white) instead of the typical blue (wet blue) chrome leather

Advantages:

• Metal-free and biodegradable (eco-friendly)

• Hypoallergenic, making it suitable for allergy-prone homes

• Accepts a wide range of dyes and coatings

Limitations:

• Slightly less durable than chrome-tanned leather

• Requires additional surface finishing for stain and water resistance

This leather type is gaining traction in luxury and green-conscious furniture design, although it still represents a small percentage of the market.

Post-Tanning Operations

Splitting the Hide Further

After tanning, the hide is often too thick for furniture use. It’s passed through a splitting machine, which divides it into:

• Grain layer (top layer, smooth and high-quality)
• Split layer (bottom portion, often used for suede or bonded leather)

Shaving and Smoothing

Hides are then shaved to uniform thickness, ensuring consistency across the entire surface. This is essential for upholstery as:

• It enables even stretching during application
• Prevents unsightly bulges or creases on furniture
• Guarantees consistent colour absorption

Sorting by Grade

Finally, the tanned hides are graded based on:

• Size
• Scarring and imperfections
• Thickness consistency
• Flexibility and colour uniformity

Premium furniture leather is usually grade A or B, with minimal marks and an even grain.

Retanning, Dyeing, and Fatliquoring

Retanning for Strength and Feel

Retanning is a secondary tanning process used to improve:

• Firmness
• Water resistance
• Touch and finish

It balances the hide’s structure, making it more suitable for heavy-duty furniture applications like recliners, sofas, and commercial seating.

Dyeing Techniques for Colour

Leather is dyed using aniline dyes (transparent) or pigmented coatings (opaque). Methods include:

• Drum dyeing: Fully penetrates the leather for rich, even colour
• Spray dyeing: Applies colour to the surface for consistency
• Hand dyeing: Used for custom or artisan leatherwork

Furniture leather is often semi-aniline dyed for both beauty and durability.

Fatliquoring for Softness and Durability

This critical process replaces natural fats removed during earlier stages. Special oils and emulsions are added to:

• Enhance softness and flexibility
• Prevent cracking over time
• Provide a protective barrier against moisture

Without fatliquoring, leather would become brittle and unfit for furniture use. It is one of the secrets behind the buttery softness found in high-end leather sofas.

Buffing and Finishing the Grain

What Is Leather Buffing?

Buffing uses light abrasion to:

• Remove surface imperfections
• Even out colour
• Prepare for finishing treatments

Buffed leather may be:

• Corrected grain: Smoothened artificially
• Natural grain: Only lightly buffed to retain texture
• Correcting Imperfections

Hides with scars or blemishes undergo:

• Sanding
• Embossing with a grain pattern
• Surface filling to mimic full-grain leather

This makes them suitable for budget-friendly furniture that still looks high-end.

Creating Different Finishes (Aniline, Semi-Aniline, Pigmented)

Aniline: Transparent dye, natural look, requires careful maintenance

Semi-Aniline: Light surface coating, combines beauty and protection

Pigmented: Opaque finish, highly durable, ideal for families and commercial use