WEIGHT
Weight for weight
Weight for weight, spider silk beats steel. That's not a lab trick.
Spider dragline silk tensile strength ≈ 1.0–1.8 GPa Spider silk density ≈ 1.3 g/cm³ vs steel ≈ 7.8 g/cm³ → silk specific strength exceeds steel Toughness: MA silk ≈ 180 MJ/m³ vs structural steel ≈ 6 MJ/m³ (≈ 30×) Spider silk is built from spidroin proteins (MaSp1, MaSp2) with crystalline polyalanine β-sheet blocks in an amorphous matrix
Gosline et al., *Phil Trans R Soc B* (2004), via PMC ( Agnarsson et al., *PLOS ONE* 5(9) e11234 (2010) (: "1652±208 MPa" Cambridge Engineering (: "Spider silk has a density nearly six times lower than steel. This combination gives it a strength-to-density ratio that exceeds steel's, making it superior on a per-weight basis."
DRAGLINE
Steel is strong partly because it's dense. Dragline silk is about six times lighter
Spider dragline silk tensile strength ≈ 1.0–1.8 GPa Spider silk density ≈ 1.3 g/cm³ vs steel ≈ 7.8 g/cm³ → silk specific strength exceeds steel Toughness: MA silk ≈ 180 MJ/m³ vs structural steel ≈ 6 MJ/m³ (≈ 30×)
Gosline et al., *Phil Trans R Soc B* (2004), via PMC ( Agnarsson et al., *PLOS ONE* 5(9) e11234 (2010) (: "1652±208 MPa" Cambridge Engineering (: "Spider silk has a density nearly six times lower than steel. This combination gives it a strength-to-density ratio that exceeds steel's, making it superior on a per-weight basis."
STRENGTH
Divide strength by weight
Divide strength by weight, and silk comes out ahead.
Spider dragline silk tensile strength ≈ 1.0–1.8 GPa Spider silk density ≈ 1.3 g/cm³ vs steel ≈ 7.8 g/cm³ → silk specific strength exceeds steel Toughness: MA silk ≈ 180 MJ/m³ vs structural steel ≈ 6 MJ/m³ (≈ 30×) MA silk extensibility ≈ 27% (can stretch ≈ a quarter of its length before snapping) Spider silk is built from spidroin proteins (MaSp1, MaSp2) with crystalline polyalanine β-sheet blocks in an amorphous matrix
Gosline et al., *Phil Trans R Soc B* (2004), via PMC ( Agnarsson et al., *PLOS ONE* 5(9) e11234 (2010) (: "1652±208 MPa" Cambridge Engineering (: "Spider silk has a density nearly six times lower than steel. This combination gives it a strength-to-density ratio that exceeds steel's, making it superior on a per-weight basis."
STRETCH
Rigid protein crystals in a stretchy matrix let a strand stretch about a quarter past its resting length before it breaks
MA silk extensibility ≈ 27% (can stretch ≈ a quarter of its length before snapping)
ACS InChemistry: "dragline silk can increase its length by 27%"
SNAPPING
it absorbs about thirty times more energy before snapping than steel
Spider silk density ≈ 1.3 g/cm³ vs steel ≈ 7.8 g/cm³ → silk specific strength exceeds steel Toughness: MA silk ≈ 180 MJ/m³ vs structural steel ≈ 6 MJ/m³ (≈ 30×) MA silk extensibility ≈ 27% (can stretch ≈ a quarter of its length before snapping)
Cambridge Engineering (: "Spider silk has a density nearly six times lower than steel. This combination gives it a strength-to-density ratio that exceeds steel's, making it superior on a per-weight basis." ACS InChemistry (: "The tensile strength of spider silk ranges from 0.45–2.0 GPa. Dragline silk is around 1.1 GPa. Depending on the specific alloy, this can be stronger than steel, which lies in the same range." ACS InChemistry: "rigid spider silk has a toughness factor of 180 megajoules/meter [MJ/m³]"
missing: assets/computed/toughness-silk-vs-steel.mp4
Next time you find a web catching the light, look closer. That's real material science, built for free.
Next time you find a web catching the light, look closer. That's real material science, built for free.
“"Spider silk is stronger than steel"”
(unqualified): FALSE for absolute tensile strength against high-grade steel. High-carbon steel wire reaches 2–6 GPa, surpassing spider silk's 1.1–1.8 GPa. Cambridge Engineering explicitly states: *"Spider silk is not stronger than steel"* on this metric. The correct, shippable claim is weight-for-weight (specific strength). Script uses "by weight" throughout.
“"Strongest material in nature"”
Darwin's bark spider silk has been called the toughest known biological material (Agnarsson 2010). This superlative is contested and not necessary — excluded.
“"Strong enough to stop a bullet / catch a jumbo jet"”
extrapolations circulate widely but are not directly sourced. Excluded.
Publishing what we refused to claim is the strongest evidence the rest was checked.