Silkworm silk vs spider thread: strength, thickness & future uses

What do you think is the strongest natural material is?

You might be surprised at where silk ranks.

Silk is an incredible material. It is lighter than cotton, but for its weight, it can be 5x stronger than steel. 

Thinner than a human hair, yet capable of holding weights that are hundreds of times its weight and size, silk can also be woven into elaborate structures which is giving scientists the power to harness silk to help humanity. 

You might have heard that spider silk has long been considered one of nature’s most durable materials, but what about silkworm thread?

Material scientists and chemists have spent a lot of time trying to mimic the silk that silkworms and spiders create as it can be so valuable. Natural silk has existed for more than 300 million years and is produced by animals belonging to the phylum Arthropoda. Silkworms, spiders, lacewings are among the creatures that can produce this incredible natural substance.

So let’s learn a little more about silk and why it’s so valuable.

When you look at silk up-close you will notice that it shimmers. With a prism-like triangular structure which refracts light to produce different colours, it is this shimmering appearance we have come to be familiar with.

Silk is beautiful, but outside of the aesthetic value and the ability to create garments, the property that most people are interested in if they are engineers – is its strength.

 

Spiders and Silkworms Produce Different Kinds of Silk

Both spiders and silkworms can produce impressive materials with surprising powers of strength, durability and elasticity. 

The silk fibres that silkworms and spiders make are some of the strongest in nature, and interestingly they are well tolerated when they are implanted in sheep, rats, and pigs. This means that they have promising applications in medicine and science. 

Spider and silkworm silks are made using unique proteins which are spun in the creature’s glands. 

Silkworms are the larva, or caterpillar, of the Bombyx silk moth and can be used for silk textile production as they are easily farmed in great numbers.

The silkworm pupates in a protective cocoon which it spins from silk secreted from its salivary glands. The cocoon’s silk is colourless and it is easily cleared of minerals, making them an ideal material for winding into a thread.

In contrast, spiders use their silk for web building, reproduction, and catching prey, although they produce comparatively small amounts.

Predatory spiders spin out their silk to make webs and cocoons, while a silkworm uses the silk to produce cocoons for metamorphoses. The fibers that they make are lightweight, elastic and strong. Both of these kinds of silk has the potential to be used in medicine, in the military and so much more. 

Ultimately, both silks have different properties of strength, but they both offer a lot of value.

 

The Difference in Silk Thickness

The difference in the thickness of the threads is typically seen to be inversely proportional to the strengths. 

Silkworms tend to make silk of a consistent thickness, while the silk produced by a spider varies in thickness. 

Silkworm threat can be as much as 10 times the thickness of spider silk and measures 0.03 inches in diameter. 

Spider silk, by comparison, is anything from 0.00032 down to as little as 0.00012 inches in diameter.

 

The Differences in Silk Strength

While both kinds of silk are incredibly strong, some scientists estimate that spider silk is more than twice as strong as silkworm silk. 

This silk is elastic and stronger than not just steel, but also Kevlar. This is particularly interesting because neither steel nor Kevlar stretch at all. Spider silk also absorbs water, making it less brittle and more elastic.

While it has been commonly believed that spider silk is stronger than silkworm silk, recent research has suggested this may not be true.

When spinning conditions are adjusted, silk from silkworms can be made stronger, stiffer and more extensible.

This could be a game changer as research develops, according to construction experts. They explain “finding new resources and new, more cost-effective ways to build infrastructure is always going to be beneficial. We see it in our industry and the same rings true for silk. The more we can harness this natural strength, the more possibilities open up.”

 

The Differences in How Silk is Made

Spider and silkworm silk are both produced in different ways and harvested differently. 

Silk has been reared since ancient Chinese times. Silkworm silk is made by the caterpillars of Bombyx mori. Their eggs hatch into larvae, and each larva spins a mile of silk thread into a cocoon.

In contrast, spiders release silk from their abdominal glands. It takes a lot of spiders to make silk cloth. It is very difficult and expensive to gather silk. This is especially the case with spiders who are territorial and will kill each other if they are forced to live in close confines. Another problem comes from the fact that spiders produce very little silk at a time.

This is reinforced by the garden waste removal team at Any Rubbish who see spiders regularly in their work. They explain “spiders can be notoriously territorial. This would make large scale commercial operations to source spider silk a challenge.”

 

Different Potential Uses of Silk

There are many benefits of raising silkworms. From teaching your children about responsibility and nature, to helping reduce anxiety and stress.

But did you know the silk produced can be used in a range of professional settings?

Silk threads are already useful for a number of medical applications. 

According to the health experts from "Get A Healthy Life", surgeons can make strong sutures using silk, and since spider silk is generally hypoallergenic it can be used for treating burns. 

They explain “silkworm silk is not as useful for this sort of application because it produces an immune response, where spider silk does not. But as medicinal research progresses we will likely see further uses for silk that can help change lives.”

Other potential applications for silkworm silk include:

• Biodegradable replacements for plastic
• Military body armour
• Sutures for wounds
• Parachutes
• Bike tyres
• Synthetic blends
• Prosthetic arteries

 

Final Thoughts

Silk is a biologically sustainable fabric and very versatile.

When you realise the surprising strength of silk, from both spiders and silkworms, it is clear that there are many potential benefits of silk.

More than pets and passion projects, silkworms may yet hold the key to advancements in medicine, technology and design.

It remains to be seen if the common uses for silkworms soon expand to include many more uses that help improve all of our lives.

Do you know of any uses for silk that we missed?

Let us know in the comments!