CaF2 vs Si (optical grade)
Glass · grade comparison
CaF2 and Si (optical grade) are both glass grades. Si (optical grade) is the stronger of the two: tensile strength 124 MPa (18 ksi) against 37 MPa (5.37 ksi) for CaF2, about 3.4 times as much. Si (optical grade) is harder — 1,100 HV against 165 HV for CaF2 — which matters for wear surfaces and threads. Si (optical grade) is lighter (2.33 g/cm³ vs 3.18 g/cm³ for CaF2) and Si (optical grade) is stiffer (130 GPa vs 75.8 GPa). On the shop floor, CaF2 machines more easily (fair vs poor).
CaF2Choose it when the part sees heat, or when the part is machined in volume.
Si (optical grade)Choose it when strength drives the design, or when surface hardness matters.
CaF2 vs Si (optical grade): 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)
Flexural Strength
Fracture Toughness (K_IC)
Hardness, Vickers
Hardness, Knoop
Hardness, Mohs
Elongation at Break
Compressive Strength
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 Constant (1 MHz)
Volume Resistivity
Dielectric Strength
Dissipation Factor (1 MHz)
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 | CaF2 | Si (optical grade) |
|---|---|---|
| Default condition | — | — |
| Relative cost | $$$$ High | $$$$ High |
| Min. machined wall | — | — |
| Best machined surface | — | — |
CaF2 vs Si (optical grade) — frequently asked
Is Si (optical grade) stronger than CaF2?
Yes. Si (optical grade) has a typical tensile strength of 124 MPa (18 ksi) against 37 MPa (5.37 ksi) for CaF2 — about 3.4 times as much.
Which is cheaper, CaF2 or Si (optical grade)?
Both sit in the same relative cost tier ($$$$, high); the part price will be decided by machining time, tolerance and quantity rather than by the material.
Which is easier to machine, CaF2 or Si (optical grade)?
CaF2. Its machinability rates fair (45/100) against poor (20/100) for Si (optical grade).
Ready to make it?
Upload a CAD file and FabDigit prices the part in CaF2 and Si (optical grade) 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.