Leather Microscopy

and the leather-like things we also call leather.

A side project.

This is a series of microscopy images of various types of leather, leather alternatives and things we may refer to as “{qualifier} leather”.

Much like milk is the liquid (cow, soy, almond, etc.) you put in your coffee or add to cereal, leather is the tough stuff in bags, clothing and food (sometimes). This is a job-centric definition used in everyday language that is occasionally contentious to industry insiders.

Open cell foam, from a Leather shoe upper.

Cactus Leather

Sample of Cactus leather by Desserto.

Three layers (from bottom to top)

  1. 500µm fibrous layer

  2. Structural textile made of yarns

  3. 500µm thick polyurethane coating consisting of at least two layers (basecoat and top coat)

Three layers (from bottom to top)

  1. 500µm thick polyurethane coating consisting of at least two layers (basecoat and top coat)

  2. 500µm fibrous layer

  3. 500µm thick polyurethane coating consisting of at least two layers (basecoat and top coat)

Reishi

Samples of Reishi by Mycoworks

Sample from a Laptop Sleeve. The product is made three layers that are bonded together to form a package - one layer including mycelium and two layers of different types of leather.

Removing the animal based components of the package, Reishi’s construction is made up of a polyester felt with mycelium cladding.

From bottom to top

  1. ~250µm Mycelium, in layers of various porosity

  2. ~800µm Felt with sparsely populated mycelium (40-60% by mass)

  3. 70µm, but highly variable in thickness top layer of mycelium

  4. 15-20µm Topcoat

Sample from a hat. Construction is made up a textile with mycelium cladding.

From bottom to top

  1. Mycelium

    1. Some areas have been locally compressed

    2. One region has what appears to be interspersed fibers of unknown composition

  2. Textile reinforcement

  3. Mycelium Layer

  4. Finish/Topcoat

Total thickness is variable but ranging between 2 and 2.5mm. This product had a moderate to strong odor described by some as “sour pickles” or “oxidized fatliquor.”

Mirum

Sample of Mirum by Natural Fiber Welding

Sampled from Allbirds Plant Pacer shoe. Construction is a homogenous rubber coating over a textile backer.

From bottom to top

  1. Structural Textile

  2. Rubber Polymer

Sampled from a Pangaia accessory made from Mirum.

Construction is a homogenous rubber coating over a textile backer.

  1. Structural Textile

  2. Rubber Polymer

Automotive

Animal Skin

Sampled from a car interior.

Material is animal skin with a PU finish.

Detail of PU Finish - approximately 60-80µm thick.

Automotive

Synthetic Leather

Synthetic leather consisting of a textile with multiple layers of PU.

Detail of textile/coating interface.

Luxury Leather

Animal Skin

SEM

Animal Skin from a Luxury Fashion House.

From bottom to top

  1. Corium (region with looser and larger fiber structure)

  2. Grain (region with tighter structure)

  3. Finish

Optical

Animal Skin from an Italian Luxury Fashion House.

From bottom to top

  1. Corium (region with looser and larger fiber structure)

  2. Grain (region with tighter structure)

  3. Finish

Luxury Syntheic Leather

Synthetic Leather from a Luxury Brand. Consists of a textile coated with a PU surface.

Synthetic leather from a luxury brand. Samples from a bag.

From bottom to top

  1. Textile (back)

  2. Expanded foam

  3. Textile

  4. PU Coating

Footwear

Animal skin bonded to nonwoven textile. Sampled from a casual sneaker.

From bottom to top

  1. Textile (back)

  2. Animal Leather

  3. PU Finish Layer

SEM

Flyleather. Samples from a casual sneaker.

Synthetic leather bonded to a foam. Sampled from a casual sneaker tongue.

From bottom to top

  1. Foam

  2. Textile

  3. PU Finish Layer

Optical

Flyleather. Sample from a casual sneaker.

Apple Leather

Sample of AppleSkin

SEM

Sample is made from a polyester textile treated/impregnated with a polyurethane coating. The filed patent claims powdered fruit waste is mixed into a polyether resin which is cross linked with isocyanate.

From Bottom to Top

  1. Structural Textile

  2. Polyurethane Layer

  3. Finish Layer

 

Optical

Optical microscopy of the same sample and region.

Pieces of material are embedded in the blue polyurethane region, these are presumed to be apple pomace.

The white fibers are the structural textile.

Fruit Leather

From Trader Joes’ Fruit Leather Wrap

Optical

Fruit Leather - stitched image

SEM

Fruit Leather - Apple Strawberry Flavor.

This was a relatively thick slab or material. The sample was largely homogenous with few observable air pockets.

Sample surface quickly degraded under the electron beam.

Paper Leather

Sample of Paper Leather from a small pouch

 

Cork Leather

SEM

Sample is a layer of cork with several layers combined into a package.

From Bottom to Top

  1. Structural Synthetic Textile

  2. Synthetic Layer

  3. Structural Fibers

  4. Synthetic Foam Layer

  5. Cork

Optical

View of entire cross section.

Optical

Cross section detail.

The interface between the black and beige region has structural fibers. These fibers are likely synthetic and appear to be transparent in color.

Leaf Leather

SEM

Sampled from a wallet.

From bottom to top

  1. Synthetic nonwoven textile

  2. Teak Leaves

  3. Finish Coating (approximately 60-70µm thick)

 

Optical

Sampled from a wallet.

From bottom to top

  1. Synthetic nonwoven textile (white)

  2. Teak Leaves (Yellow)

  3. Finish Coating (transparent/amber)