Grade A Lava
also AlSiMag Grade A
Grade A Lava (AlSiMag Grade A) is a talc-based aluminum-silicate ceramic soft enough to be turned, milled and drilled like soapstone in the unfired state, then fired to a hard insulating body.
Reference datasheet — Grade A Lava is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the FIRED condition
Grade A Lava tempers and conditions
Grade A Lava is supplied in 2 conditions, soft to hard. FIRED is the default FabDigit quotes; the values on this page are for it.
Compare all 2 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
as-supplied soft blank for free machining | Buy in this state to cut complex shapes with ordinary HSS tooling; not a service material — soft, weak and moisture/heat sensitive until fired. | 8 | 1 W/m·K | |||
FIREDDefault Machined green, then kiln-fired ~1000–1100 °C to full hardness | Use for the finished service part: hard, heat- and arc-resistant silicate insulator after firing (allow ~2 % shrinkage). | 25 | 350 HV | 2 W/m·K |
What is Grade A Lava?
Grade A Lava (AlSiMag Grade A) is a talc-based aluminum-silicate ceramic soft enough to be turned, milled and drilled like soapstone in the unfired state, then fired to a hard insulating body. It suits one-off RF coil forms and vacuum-tube insulators machined directly from unfired blanks and rods. Fired properties are modest — 2.25 g/cm³, 25 MPa tensile strength, 50 GPa modulus, 1.7 W/m·K and 1090 °C maximum service — and the body shrinks about 2 % and remains porous, so tight tolerances need post-fire diamond grinding. Machinable glass-ceramic is the alternative when parts must hold size without a firing step. Grade A Lava has a density of 2.25 g/cm³ (0.0813 lb/in³), lighter than 86% of ceramic grades. Grade A Lava has a tensile strength of 25 MPa (3.63 ksi), weaker than 85% of ceramic grades. The elastic modulus is 50 GPa (7.25 Msi).
What is Grade A Lava used for?
- RF coil forms
- vacuum tube insulators
- machined prototype insulating parts
Advantages
- Low embodied carbon — 1.4 kg CO₂/kg, better than 98% of ceramic grades
- Lightweight — 2.25 g/cm³ (0.0813 lb/in³), better than 86% of ceramic grades
- Easy to machine — 15/100, better than 81% of ceramic grades
Limitations
- Hard to polish — 35/100, worse than 93% of ceramic grades
- Poor heat conductor — 1.7 W/m·K (0.982 BTU/hr·ft·°F), worse than 90% of ceramic grades
- Low stiffness — 50 GPa (7.25 Msi), worse than 84% of ceramic grades
Grade A Lava properties
Typical room-temperature values for Grade A Lava-FIRED; bars are the position among ceramic grades.
Physical2
Grade A Lava has a density of 2.25 g/cm³ (0.0813 lb/in³), lighter than 86% of ceramic grades.
Mechanical10
Grade A Lava has a tensile strength of 25 MPa (3.63 ksi), weaker than 85% of ceramic grades. The elastic modulus is 50 GPa (7.25 Msi).
Thermal5
Grade A Lava is rated for continuous service to 1,090°C (1,994 °F). It conducts heat at 1.7 W/m·K (0.982 BTU/hr·ft·°F), worse than 90% of ceramic grades. Thermal expansion is 8 µm/m·K (4.44 µin/in·°F).
Electrical5
Grade A Lava is an electrical insulator with a dielectric strength of 8 kV/mm (203.2 V/mil) and a resistivity of 1×10¹⁰ Ω·m.
Chemical & Environmental2
Corrosion resistance is very good (80/100), better than 56% of ceramic grades.
Sustainability4
Producing a kilogram of Grade A Lava takes about 20 MJ of energy and emits 1.4 kg of CO₂ — less than 98% of ceramic grades. Typical recycled content is 0%.
Manufacturability3
Grade A Lava's machinability is poor (15/100, better than 81% of ceramic grades).
Common Calculations4
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the ceramic family
Yield strength against density for every ceramic grade FabDigit runs. Grade A Lava is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Grade A Lava
Is Grade A Lava easy to machine?
Machine unfired with sharp HSS tools, no coolant and good dust extraction (respirable silica); fired parts need diamond grinding only.
Can Grade A Lava be welded?
Not weldable — join by ceramic cement, glass frit, or mechanical clamping/metallizing.
Can Grade A Lava be formed, bent or molded?
Shape entirely by subtractive machining of the green blank; allow ~2 % linear shrinkage and slow ramp firing to ~1000–1100 °C with a dwell to avoid cracking.
Grade A Lava chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| SiO2as hydrous aluminium silicate (pyrophyllite/talc mineral base) | 55 – 66 | 61 |
| Al2O3 | 24 – 32 | 29 |
| MgOfrom talc content | 0.5 – 5 | 2 |
| Fe2O3 | 0.2 – 1.5 | 0.7 |
| K2O+Na2Oalkali flux, raises dielectric loss | 0.2 – 2 | 0.8 |
| LOI (chemically bound H2O)driven off during firing; cause of ~2 % shrinkage | 3 – 6 | 5 |
| CaO/TiO2 and other minor oxidesbalance, natural mineral impurities | balance |
What surface finishes work on Grade A Lava?
Fired surface is porous: impregnate with wax, silicone or resin, or glaze, for moisture-sensitive RF and vacuum use; metallize for solder/braze seals.
Equivalent designations
Standards and trade names that resolve to Grade A Lava in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- Trade names
- AlSiMag Grade A
How much does Grade A Lava cost?
Grade A Lava is a high-cost ceramic ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Grade A Lava — frequently asked
What is Grade A Lava used for?
Grade A Lava is typically used for RF coil forms, vacuum tube insulators and machined prototype insulating parts. In short: machines before firing; low-cost prototype ceramic; porous fired surface.
What is the tensile strength of Grade A Lava?
Grade A Lava has a typical tensile strength of 25 MPa (3.63 ksi) — weaker than 85% of ceramic grades. Strength varies by condition: see the 2 listed tempers.
Is Grade A Lava easy to machine?
Not especially — machinability is rated poor (15/100, better than 81% of ceramic grades). Machine unfired with sharp HSS tools, no coolant and good dust extraction (respirable silica); fired parts need diamond grinding only.
Can Grade A Lava be welded?
Not weldable — join by ceramic cement, glass frit, or mechanical clamping/metallizing.
What surface finishes work on Grade A Lava?
Fired surface is porous: impregnate with wax, silicone or resin, or glaze, for moisture-sensitive RF and vacuum use; metallize for solder/braze seals.
Can Grade A Lava be formed, bent or molded?
Shape entirely by subtractive machining of the green blank; allow ~2 % linear shrinkage and slow ramp firing to ~1000–1100 °C with a dwell to avoid cracking.
What is the maximum service temperature of Grade A Lava?
Grade A Lava is rated for continuous use to about 1,090°C (1,994 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does Grade A Lava cost?
Grade A Lava is a high-cost ceramic ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASM Engineered Materials Handbook Vol. 4: Ceramics and Glasses — ASM International (1991)
- Machinable lava (hydrous aluminum silicate) grade A blank data — Ceramic materials distributor datasheets (2020)
- ASTM C242 Standard Terminology of Ceramic Whitewares and Related Products — ASTM (2020)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.