Fused Silica vs KRS-5
Glass · grade comparison
Fused Silica and KRS-5 are both glass grades. Fused Silica is the stronger of the two: tensile strength 50 MPa (7.25 ksi) against 26 MPa (3.77 ksi) for KRS-5, about 92% more. In exchange, KRS-5 is the more ductile: elongation 2% versus 0% for Fused Silica, and Fused Silica is harder (700 HV vs 40 HV). Fused Silica is lighter (2.2 g/cm³ vs 7.37 g/cm³ for KRS-5) and Fused Silica is stiffer (72 GPa vs 15.9 GPa). On the shop floor, KRS-5 machines more easily (good vs not recommended) and Fused Silica sits in a lower cost tier (standard, $$) than KRS-5 (high, $$$$).
Fused SilicaChoose it when strength drives the design, or when weight is the constraint.
KRS-5Choose it when the part is bent, formed or impact-loaded, or when the part is machined in volume.
Fused Silica vs KRS-5: propertiesHow to read these bars
- One bar per material. A full bar is the highest value among all glass grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
How to read these bars
- One bar per material. A full bar is the highest value among all glass grades in the FabDigit library; each bar is drawn as a share of that.
- The better value (by the usual engineering direction) is in bold. Rows with no direction — density, thermal conductivity — have no bold.
- Values are typical room-temperature figures for the condition named on each card.
- Confirm against the certified mill or resin datasheet before design release.
Mechanical
Strength, stiffness, ductility and hardness at room temperature.
Elastic (Young's) Modulus
Shear Modulus
Bulk Modulus
Poisson's Ratio
Tensile Strength (Ultimate)
Elongation at Break
Compressive Strength
Flexural Strength
Shear Strength
Fracture Toughness (K_IC)
Hardness, Vickers
Hardness, Knoop
Hardness, Mohs
Physical
Density and transition temperatures.
Density
Melting Point (Solidus)
Refractive Index
Light Transmission
Same in both: Porosity 0%
Thermal
How each material carries heat and how hot it can run.
Thermal Conductivity
Specific Heat Capacity
Thermal Expansion (CTE, 20–100 °C)
Max Service Temperature (continuous)
Min Service Temperature
Electrical
Conductivity and insulation.
Electrical Resistivity
Dielectric Strength
Dielectric Constant (1 MHz)
Dissipation Factor (1 MHz)
Volume Resistivity
Chemical & Environmental
Corrosion and environmental resistance (0–100 scores).
Corrosion Resistance
Manufacturability
FabDigit workshop ratings (0–100 scores) — how each material behaves on the machine.
Machinability
Polishability
Sustainability
Primary-production footprint per kilogram.
Embodied Energy (primary production)
Embodied Carbon (primary production)
Embodied Water
Typical Recycled Content
Common Calculations
Ratios derived from the values above.
Specific Strength (UTS / density)
Specific Stiffness (E / density)
Thermal Diffusivity
Thermal Shock Resistance Index
Strength versus weight
Yield strength against density for every glass grade in the FabDigit library; the compared grades are highlighted. Up and left is stronger for its weight.
Manufacturing and finishing
| Capability | Fused Silica | KRS-5 |
|---|---|---|
| Default condition | Annealed Glass | — |
| Relative cost | $$ Standard | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
Fused Silica vs KRS-5 — frequently asked
Is Fused Silica stronger than KRS-5?
Yes. Fused Silica has a typical tensile strength of 50 MPa (7.25 ksi) against 26 MPa (3.77 ksi) for KRS-5 — about 92% more.
Which is cheaper, Fused Silica or KRS-5?
Fused Silica is the lower-cost material: it sits in the standard tier ($$) while KRS-5 is high ($$$$). Part price depends far more on geometry, tolerance and quantity than on raw stock — upload a CAD file for a live quote.
Which is easier to machine, Fused Silica or KRS-5?
KRS-5. Its machinability rates good (55/100) against not recommended (10/100) for Fused Silica.
Ready to make it?
Upload a CAD file and FabDigit prices the part in Fused Silica and KRS-5 side by side — material, machining time, tolerance and finish in one quote. Certified material data ships with the order on request.
Typical handbook values for the conditions named above, normalised for comparison. Hardness on non-Brinell scales is converted approximately for charting only. Request certified data with your order for design-critical properties.