spore: profile
id: macor
spore_version: 0.2
family: technical-ceramics
name: Macor
abbreviation: MGC
role: machinable insulator
category: ceramics
type: glass-ceramics
summary: |
  MACOR is Corning's machinable glass-ceramic: a white, zero-porosity material made of about 55 % fluorophlogopite mica in a borosilicate glass matrix. It is cut with ordinary metalworking tools and needs no post-firing, and Corning rates it for continuous use at 800 °C with a peak of 1000 °C under no load. The Corning datasheet gives a modulus of rupture of 94 MPa, a Young's modulus of 66.9 GPa and a thermal conductivity of 1.46 W/m°C at 25 °C.
best_for: Machined insulators and fixtures that must hold tight tolerances, stay stable to 800 °C and not outgas in vacuum
weakest_at: 'Strength and toughness: 94 MPa modulus of rupture and 1.53 MPa m0.5 fracture toughness, against 345 MPa compressive strength'
identity:
  formula: Fluorophlogopite mica in a borosilicate glass matrix, about 55 % mica and 45 % glass by weight (Corning)
  cas: 66402-68-4
  source: boedeker-macor-sds
  where: Section 3, CAS 66402-68-4 printed for 'Ceramic materials and wares, chemicals' at 100 %
  designations:
    - system: Trade name
      code: MACOR
      source: corning-macor-datasheet
      where: Front page, title and trademark notice
    - system: Trade name
      code: MGC
      source: corning-macor-datasheet
      where: Applications page (p. 2), text 'MACOR MGC'
    - system: Trade name
      code: '9657'
      note: Corning glass code printed for MACOR (2015 sheet)
      source: boedeker-macor-sds
      where: Section 1, Glass Code 9657
    - system: Trade name
      code: '9658'
      note: Corning glass code 9658 for MACOR Machinable Glass-Ceramic (2008 sheet)
      source: rs-macor-sds-2008
      where: Page 1, Material Name line
tags:
  environments: []
  stresses:
    - vacuum-and-outgassing
    - total-radiation-dose
  applications:
    - structures
    - thermal-control
    - electronics-and-chips
    - optics-and-cameras
properties:
  - benchmark: density
    label: Density, MACOR
    value: 2.52
    unit: g/cm3
    scope: material
    conditions:
      form: fully dense, 0 % porosity
      temperature: not stated in the datasheet table
    method: Value printed in the Corning MACOR datasheet; Morgan and Goodfellow print the same 2.52
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Mechanical column, Density 2.52 g/cm3
  - benchmark: elastic_modulus
    label: Young's modulus, MACOR
    value: 66.9
    unit: GPa
    scope: material
    conditions:
      temperature: 25 °C
    method: Printed in the Corning datasheet as 66.9 GPa (9.7x10^6 psi); Morgan prints 68 GPa for the same material, not used here
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Mechanical column, Young's Modulus 25 °C
  - benchmark: shear_modulus
    label: Shear modulus, MACOR
    value: 25.5
    unit: GPa
    scope: material
    conditions:
      temperature: 25 °C
    method: Value printed in the Corning datasheet; the name shear_modulus is not in the canonical property file
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Mechanical column, Shear Modulus 25 °C 25.5 GPa
  - benchmark: flexural_strength
    label: Modulus of rupture (flexural strength), Corning
    value: 94
    unit: MPa
    scope: material
    conditions:
      temperature: 25 °C
      basis: minimum specified average value
      form: fully dense sample quantities tested by Corning
    method: Printed as 94 MPa (13,600 psi) in the Corning datasheet, with the note that actual characteristics of production lots may vary
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Mechanical column, Modulus of Rupture 25 °C, 94 MPa minimum specified average value
  - benchmark: flexural_strength
    label: Flexural strength, MACOR (Morgan table)
    value: 89
    unit: MPa
    scope: material
    conditions:
      temperature: not stated
      basis: MACOR column of the material comparison table
    method: Value printed in the Morgan comparison table; differs from the Corning 94 MPa, both are kept
    status: ground
    source: morgan-macor
    where: Property table, row Flexural Strength, MACOR column (89 MPa)
  - benchmark: compressive_strength
    label: Compressive strength, MACOR
    value: 345
    unit: MPa
    scope: material
    conditions:
      temperature: not stated
    method: Printed as 345 MPa (50,000 psi) in the Corning datasheet
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Mechanical column, Compressive strength 345 MPa
  - benchmark: fracture_toughness
    label: Fracture toughness, MACOR
    value: 1.53
    unit: MPa m0.5
    scope: material
    conditions:
      temperature: not stated
    method: Unit as printed in the Corning datasheet (also 1,390 psi in0.5)
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Mechanical column, Fracture Toughness 1.53 MPa m0.5
  - benchmark: knoop_hardness
    label: Knoop hardness, MACOR
    value: 250
    unit: kg/mm2
    scope: material
    conditions:
      load: 100 g
      unit_in_source: printed without unit in the Corning datasheet, unit taken from the Morgan row
    method: Morgan prints the unit kg/mm2 and the value 250 for MACOR; Corning prints Knoop 100 g = 250 with no unit
    status: ground
    source: morgan-macor
    where: Property table, row Knoop Hardness, unit column kg/mm2, MACOR column 250
  - benchmark: cte
    label: Coefficient of thermal expansion, 25 to 300 °C
    value: 9.3
    unit: ppm/K
    scope: material
    conditions:
      temperature_range: 25 to 300 °C
      unit_in_source: 93x10-7/°C
    method: Printed as 93x10-7/°C in the Corning datasheet; converted to ppm/K (1 ppm/K = 10-6/K). Morgan prints 9.3 x10-6 for the same range.
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Thermal column, Coefficient of Expansion 25-300 °C, 93x10-7/°C
  - benchmark: cte
    label: Coefficient of thermal expansion, 25 to 800 °C
    value: 12.6
    unit: ppm/K
    scope: material
    conditions:
      temperature_range: 25 to 800 °C
      unit_in_source: 126x10-7/°C
    method: Printed as 126x10-7/°C in the Corning datasheet; converted to ppm/K
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Thermal column, Coefficient of Expansion 25-800 °C, 126x10-7/°C
  - benchmark: specific_heat
    label: Specific heat, MACOR
    value: 0.79
    unit: kJ/kg°C
    scope: material
    conditions:
      temperature: 25 °C
    method: Printed as .79 KJ/kg°C in the Corning datasheet
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Thermal column, Specific Heat 25 °C
  - benchmark: thermal_conductivity
    label: Thermal conductivity, MACOR
    value: 1.46
    unit: W/m°C
    scope: material
    conditions:
      temperature: 25 °C
    method: Printed as 1.46 W/m°C in the Corning datasheet; Morgan prints 1.46 W/m.K for the same grade
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Thermal column, Thermal Conductivity 25 °C
  - benchmark: thermal_diffusivity
    label: Thermal diffusivity, MACOR
    value: 7.3e-7
    unit: m2/s
    scope: material
    conditions:
      temperature: 25 °C
    method: Printed as 7.3x10-7 m2/s in the Corning datasheet
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Thermal column, Thermal Diffusivity 25 °C
  - benchmark: max_service_temp
    label: Continuous operating temperature, MACOR
    value: 800
    unit: °C
    scope: material
    conditions:
      basis: continuous use
    method: Printed as 800 °C (1472 °F) in the Corning datasheet
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Thermal column, Continuous Operating Temperature 800 °C
  - benchmark: max_service_temp
    label: Maximum no-load temperature, MACOR
    value: 1000
    unit: °C
    scope: material
    conditions:
      basis: peak, maximum no-load temperature
    method: Printed as 1000 °C (1832 °F) in the Corning datasheet; Morgan also lists 1000 °C
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Thermal column, Maximum No Load Temperature 1000 °C
  - benchmark: dielectric_constant
    label: Dielectric constant, 1 kHz
    value: 6.03
    unit: '-'
    scope: material
    conditions:
      frequency: 1 kHz
      temperature: 25 °C
    method: Printed in the Corning datasheet, Electrical column
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Electrical column, Dielectric Constant 25 °C, 1 KHz 6.03
  - benchmark: dielectric_constant
    label: Dielectric constant, 8.5 GHz
    value: 5.67
    unit: '-'
    scope: material
    conditions:
      frequency: 8.5 GHz
      temperature: 25 °C
    method: Printed in the Corning datasheet, Electrical column
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Electrical column, Dielectric Constant 25 °C, 8.5 GHz 5.67
  - benchmark: dissipation_factor
    label: Loss tangent, 1 kHz
    value: 0.0047
    unit: '-'
    scope: material
    conditions:
      frequency: 1 kHz
      temperature: 25 °C
    method: Printed as 4.7x10-3 in the Corning datasheet
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Electrical column, Loss Tangent 25 °C 1 KHz 4.7x10-3
  - benchmark: dielectric_strength
    label: Dielectric strength, AC average
    value: 9.4
    unit: kV/mm
    scope: material
    conditions:
      thickness: 12 mil
      temperature: 25 °C
      basis: AC, average
    method: Printed as 9.4 KV/mm with 785 V/mil in the Corning datasheet. The printed pair does not agree (785 V/mil is about 30.9 kV/mm), so treat this value with care.
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Electrical column, Dielectric Strength (AC) avg. at 12 mil and 25 °C
  - benchmark: dielectric_strength
    label: Dielectric strength, DC average
    value: 62.4
    unit: kV/mm
    scope: material
    conditions:
      thickness: 12 mil
      temperature: 25 °C
      basis: DC, average
    method: Printed as 62.4 KV/mm with 5206 V/mil in the Corning datasheet. The printed pair does not agree (5206 V/mil is about 205 kV/mm), and Morgan prints 39.4 and Goodfellow 129 kV/mm for DC, so this value is unresolved.
    status: ground
    source: corning-macor-datasheet
    where: Properties page (p. 4), Electrical column, Dielectric Strength (DC) avg. at 12 mil and 25 °C
  - benchmark: ultimate_tensile_strength
    label: Tensile strength, design properties
    value: 90
    unit: MPa
    scope: material
    conditions:
      temperature: not stated
      basis: design-properties table on the page
    method: Printed in the design-properties table of the SpotMaterial database page; no test condition printed
    status: ground
    source: spotmaterial-macor
    where: Design properties table, row Tensile strength 90 MPa
corrosion:
  - environment: 5 % hydrochloric acid, pH 0.1, 24 h at 95 °C
    headline: 'Hydrochloric acid is the most aggressive test on the datasheet: about 100 mg/cm2 weight loss in 24 h.'
    effect: Weight loss of about 100 mg/cm2 in the Corning test, the largest of the chemical tests printed on the datasheet.
    rating: severe
    conditions:
      solution: 5 % HCl
      pH: '0.1'
      time: 24 h
      temperature: 95 °C
      measure: gravimetric weight loss
    source: corning-macor-datasheet
    where: Properties page (p. 4), section IV Chemical, Weight Loss table, 5 % HCL row ~100 mg/cm2
  - environment: 5 % sodium hydroxide, pH 13.2, 6 h at 95 °C
    headline: 'Sodium hydroxide attacks Macor moderately: about 10 mg/cm2 in 6 h.'
    effect: Weight loss of about 10 mg/cm2 in the Corning test.
    rating: moderate
    conditions:
      solution: 5 % NaOH
      pH: '13.2'
      time: 6 h
      temperature: 95 °C
      measure: gravimetric weight loss
    source: corning-macor-datasheet
    where: Properties page (p. 4), section IV Chemical, Weight Loss table, 5 % NaOH row ~10 mg/cm2
  - environment: 0.002 N nitric acid, pH 2.8, 24 h at 95 °C
    headline: Dilute nitric acid causes only small weight loss.
    effect: Weight loss of about 0.6 mg/cm2 in the Corning test.
    rating: low
    conditions:
      solution: 0.002 N HNO3
      pH: '2.8'
      time: 24 h
      temperature: 95 °C
      measure: gravimetric weight loss
    source: corning-macor-datasheet
    where: Properties page (p. 4), section IV Chemical, Weight Loss table, 0.002 N HNO3 row ~0.6 mg/cm2
  - environment: 0.1 N sodium bicarbonate, pH 8.4, 24 h at 95 °C
    headline: Sodium bicarbonate causes little weight loss.
    effect: Weight loss of about 0.3 mg/cm2 in the Corning test.
    rating: low
    conditions:
      solution: 0.1 N NaHCO3
      pH: '8.4'
      time: 24 h
      temperature: 95 °C
      measure: gravimetric weight loss
    source: corning-macor-datasheet
    where: Properties page (p. 4), section IV Chemical, Weight Loss table, 0.1 N NaHCO3 row ~0.3 mg/cm2
  - environment: 0.02 N sodium carbonate, pH 10.9, 6 h at 95 °C
    headline: Sodium carbonate causes very little weight loss.
    effect: Weight loss of about 0.1 mg/cm2 in the Corning test.
    rating: low
    conditions:
      solution: 0.02 N Na2CO3
      pH: '10.9'
      time: 6 h
      temperature: 95 °C
      measure: gravimetric weight loss
    source: corning-macor-datasheet
    where: Properties page (p. 4), section IV Chemical, Weight Loss table, 0.02 N Na2CO3 row ~0.1 mg/cm2
  - environment: Vacuum after proper bake-out
    headline: Macor does not outgas in vacuum when it is properly baked out.
    effect: Corning says it is clean, with no outgassing and zero porosity, and does not outgas in vacuum environments when properly baked out.
    rating: none
    conditions:
      basis: properly baked out, as stated by Corning; no outgassing number printed
    source: corning-macor-datasheet
    where: Front page feature list and Properties page (p. 4), last paragraph
  - environment: Acid and alkali classes (DIN, as printed by Goodfellow)
    headline: Goodfellow prints DIN water class HGB2, acid class 4 and alkali class A3 for MACOR.
    effect: Classes printed as a list of codes on the product page; the page does not state what each class means.
    rating: unknown
    conditions:
      standard: DIN classes as printed, no test values
    source: goodfellow-macor-bar
    where: Chemical Resistance table, rows DIN Water Class HGB2, DIN Acid Class 4, DIN Alkali Class A3
risks:
  hazards:
    - text: Not classified under 29 CFR 1910.1200 in the Boedeker copy of the Corning SDS; no GHS symbol, signal word or hazard statement is assigned.
      ghs: []
      source: boedeker-macor-sds
      where: Section 2, Classification and GHS label elements
    - text: Exposure to glass powder or dusts may be irritating to eyes, nose and throat, and at very high exposure levels the dust may affect the lungs (2008 Corning sheet, Glass Code 9658).
      ghs: []
      source: rs-macor-sds-2008
      where: Section 2, Emergency Overview
    - text: The dust created in machining can be an irritant; Corning says this can be avoided with good housekeeping and appropriate machining technique.
      ghs: []
      source: corning-macor-datasheet
      where: Composition page (p. 7)
  failure_risks:
    - mode: Brittle fracture rather than yielding
      trigger: Mechanical overload; Corning gives 94 MPa as the minimum average modulus of rupture and 1.53 MPa m0.5 fracture toughness
      consequence: Corning says that, unlike ductile materials, MACOR won't deform; a crack is therefore not blunted by plastic flow (reading of the datasheet, not a failure test).
      severity: high
      source: corning-macor-datasheet
      where: Properties page (p. 4), Mechanical column; front page Properties paragraph (p. 1)
    - mode: Use above the rated temperature
      trigger: Continuous use above 800 °C or no-load temperature above 1000 °C
      consequence: Corning gives only 800 °C continuous and 1000 °C peak no-load ratings; no data are printed for loaded use at higher temperatures.
      severity: moderate
      source: corning-macor-datasheet
      where: Properties page (p. 4), Thermal column
    - mode: Dissolution in strong acid
      trigger: 5 % HCl at 95 °C for 24 h
      consequence: About 100 mg/cm2 weight loss in the Corning test.
      severity: moderate
      source: corning-macor-datasheet
      where: Properties page (p. 4), section IV Chemical
  side_effects:
    - text: Machining produces fine dust that can irritate; the dust must be kept off surfaces and out of the air.
      affects: Machine operators and the shop
      source: boedeker-macor-sds
      where: Section 6, Methods for containment and cleaning up; Section 7, Minimize dust generation
  handling:
    - text: Avoid breathing dust and wash thoroughly after handling; keep the container closed and store in a dry area.
      source: boedeker-macor-sds
    - text: Use a water-soluble coolant when machining; Corning recommends Cimstar 40 - Pink for cutting and grinding glass or ceramics.
      source: corning-macor-datasheet
    - text: Use carbide tools for longer wear; high-speed steel can be used.
      source: corning-macor-datasheet
  mitigations:
    - text: Use a dust suppressant or HEPA vacuum when crushed glass can make airborne dust.
      source: boedeker-macor-sds
    - text: Use good housekeeping so dust does not build up on surfaces.
      source: boedeker-macor-sds
uses:
  - application: structures
    device: Retaining rings at hinge points, windows and doors of the Space Shuttle Orbiter
    example: Corning says over 200 distinctly shaped MACOR parts are on the Space Shuttle Orbiter, with retaining rings at all hinge points, windows and doors. The claim is the manufacturer's own.
    source: corning-macor-datasheet
    where: Applications page (p. 2-3), Aerospace Industry section
  - application: structures
    device: Frame of a NASA spaceborne gamma radiation detector
    example: Large pieces of MACOR are used in a NASA spaceborne gamma radiation detector; frame corners are joined by butt-lap mechanical joints and a sealing glass. Corning's claim, not checked against a NASA document.
    source: corning-macor-datasheet
    where: Applications page (p. 2-3), Aerospace Industry section
  - application: thermal-control
    device: Supports and components in several satellite-borne systems
    example: Precision Ceramics, the UK distributor, says MACOR supports and components in satellite-borne systems, giving thermal and electrical insulation. No mission named.
    source: precision-ceramics-macor
    where: Aerospace/Space Industry section, second bullet
  - application: electronics-and-chips
    device: Coil supports and vacuum feed-throughs for ultra-high-vacuum equipment
    example: MACOR is used as an insulator or coil support and for vacuum feed-throughs, with a compatible sealing glass giving a vacuum-tight seal.
    source: corning-macor-datasheet
    where: Applications page (p. 2-3), Ultra-High Vacuum Environments section
  - application: optics-and-cameras
    device: Spacers, cavities and reflectors in laser assemblies
    example: Precision Ceramics lists spacers, cavities and reflectors in laser assemblies, citing the precision finish and heat resistance of the material.
    source: precision-ceramics-macor
    where: Laser Applications section
supply:
  - subject: MACOR (Corning Incorporated product)
    abundance: Not stated in the fetched sources; a manufactured glass-ceramic, not a raw material
    producers: []
    critical_lists: []
    recycling: The SDS says glass products may be recycled; Corning SAS, Nemours, France, is listed as the supplier on the 2015 sheet.
    substitutes: []
    source: boedeker-macor-sds
    where: Section 1, Manufacturer Information; Section 6, Methods for containment and cleaning up
documents:
  - title: MACOR Machinable Glass Ceramic datasheet (Corning, MACOR 01)
    type: datasheet
    url: https://psec.uchicago.edu/ceramics/MACOR%20Data%20Sheet.pdf
  - title: MACOR Machinable Glass Ceramic, Morgan Advanced Materials product page
    type: datasheet
    url: https://www.morgantechnicalceramics.com/en-gb/materials/macor/
  - title: MACOR Machinable Glass Ceramic Bar, Goodfellow product page (product 1000126059)
    type: datasheet
    url: https://www.goodfellow.com/usa/macor-glass-ceramic-bar-1000126059
  - title: Macor, Wikipedia
    type: database
    url: https://en.wikipedia.org/wiki/Macor
  - title: Safety Data Sheet MACOR, SDS ID C-587, Boedeker copy (2015)
    type: sds
    url: https://www.boedeker.com/Portals/0/Safety%20Data%20Sheets%20SDS/Macor-Ceramic-SDS-Safety-Data-Sheet-Boedeker-08-27-2015.PDF
    year: 2015
  - title: Safety Data Sheet Glass Code 9658, MACOR Machinable Glass-Ceramic, Corning copy (2008)
    type: sds
    url: https://docs.rs-online.com/40ac/0900766b8128c272.pdf
    year: 2008
  - title: MACOR Machinable Glass Ceramic brochure, Precision Ceramics (UK distributor)
    type: datasheet
    url: https://cdn.abicart.com/shop/ws28/75628/art18/156029318-4b33a9-Macor-Machinable-Glass-Ceramic.pdf
  - title: MACOR Machinable Glass Ceramic properties, SpotMaterial design properties
    type: database
    url: https://spotmaterial.com/material/glass-ceramic/machinable-glass-ceramic-mgc-macor/
gaps:
  - No flight or NASA document was opened for the Space Shuttle parts or the gamma detector; the uses rest on Corning and Precision Ceramics statements and are marked as manufacturer claims.
  - The Corning product page (corning.com) returned HTTP 403 and was not read.
  - The Sheffield DoITPOMS micrograph record returned 403; the house-of-cards microstructure description was seen only in a search snippet, so it is not recorded.
  - The dielectric strength pairs printed by Corning do not match their own V/mil conversions, and Morgan (DC 39.4 kV/mm) and Goodfellow (DC 129 kV/mm, AC 45 kV/mm) print different values; the conflict is kept in the method fields.
  - 'DC volume resistivity differs between sources: Corning and Goodfellow give 10^16 and 10^17 ohm-cm, Morgan gives >10^14 ohm-cm. The Corning value (printed as >10^16 ohm-cm) lost its superscript in the PDF text, so the verifier could not match it and it is not entered.'
  - No UNS, EN, ASTM, AISI or other standard grade designation was found for MACOR; it is a proprietary trade product. The Corning glass code 9657 (SDS) and 9658 (2008 sheet) are recorded as trade-name designations.
  - No manufacturing process, production country share or critical-mineral listing was found for MACOR in the fetched sources; the supply entry says so.
  - No total mass loss, collected volatile condensable material, atomic oxygen or radiation dose number was found for MACOR, so the vacuum and radiation stresses rest on qualitative statements only.
  - Poisson's ratio (0.29, Corning) is not entered because the benchmark name is not in the canonical property file.
  - Glass-transition or softening temperature and the viscosity of the glass phase were not found.
  - No ISO or ASTM test standard was found for the modulus of rupture or the fracture toughness; the test method is not named by the datasheet.
sources:
  corning-macor-datasheet:
    title: MACOR Machinable Glass Ceramic datasheet (Corning Incorporated, MACOR 01)
    url: https://psec.uchicago.edu/ceramics/MACOR%20Data%20Sheet.pdf
    year: 2026
    kind: datasheet
    license: Manufacturer datasheet (cited, not reproduced)
  morgan-macor:
    title: MACOR Machinable Glass Ceramic, Morgan Advanced Materials (Technical Ceramics), properties table
    url: https://www.morgantechnicalceramics.com/en-gb/materials/macor/
    year: 2026
    kind: datasheet
    license: Manufacturer web page (cited, not reproduced)
  goodfellow-macor-bar:
    title: MACOR Machinable Glass Ceramic Bar 20 mm x 20 mm, Goodfellow product 1000126059
    url: https://www.goodfellow.com/usa/macor-glass-ceramic-bar-1000126059
    kind: datasheet
    license: Distributor web page (cited, not reproduced)
  wikipedia-macor:
    title: Macor, Wikipedia
    url: https://en.wikipedia.org/wiki/Macor
    kind: web
    license: CC BY-SA 4.0 (cited, not reproduced)
  boedeker-macor-sds:
    title: Safety Data Sheet MACOR, SDS ID C-587, Revision 2.0 (2015), copy hosted by Boedeker
    url: https://www.boedeker.com/Portals/0/Safety%20Data%20Sheets%20SDS/Macor-Ceramic-SDS-Safety-Data-Sheet-Boedeker-08-27-2015.PDF
    year: 2015
    kind: datasheet
    license: Safety data sheet (cited, not reproduced)
  rs-macor-sds-2008:
    title: Safety Data Sheet Glass Code 9658, MACOR Machinable Glass-Ceramic, ID C-046, Revision 5.0 (2008), copy hosted by RS
    url: https://docs.rs-online.com/40ac/0900766b8128c272.pdf
    year: 2008
    kind: datasheet
    license: Safety data sheet (cited, not reproduced)
  precision-ceramics-macor:
    title: MACOR Machinable Glass Ceramic brochure, Precision Ceramics (UK distributor), Birmingham
    url: https://cdn.abicart.com/shop/ws28/75628/art18/156029318-4b33a9-Macor-Machinable-Glass-Ceramic.pdf
    kind: datasheet
    license: Distributor brochure (cited, not reproduced)
  spotmaterial-macor:
    title: Machinable glass ceramic (MGC) MACOR, SpotMaterial design properties
    url: https://spotmaterial.com/material/glass-ceramic/machinable-glass-ceramic-mgc-macor/
    kind: web
    license: Database web page (cited, not reproduced)
license: CC-BY-4.0
updated: '2026-10-26'
review:
  status: draft
  method: assistant
  checked_values: 21
  unreachable: 3
  caveats: 5
  note: 'Values were read by an AI assistant on 2026-10-26 from the pages and PDFs named in each entry. Unreachable: the Corning product page and the DoITPOMS micrograph record (both HTTP 403) and a Malaysian university PDF that did not download. Caveats: the Corning dielectric strength pairs do not match their own V/mil values; resistivity and dielectric strength differ between manufacturers; the Space Shuttle and gamma-detector uses are manufacturer claims; supply shares were not found.'
story:
  risk_groups:
    - title: For people
      lead: The sources agree that MACOR is not a hazardous substance under the Corning SDS, but its dust is an irritant.
      level: 1
      verdict: Low hazard as a solid, dust is the concern
      points:
        - label: As a solid
          line: The 2015 Boedeker copy of the Corning SDS assigns no GHS class, symbol or hazard statement.
        - label: Dust
          line: The 2008 Corning sheet says glass powder or dust may irritate the eyes, nose and throat, and that very high exposure may affect the lungs.
    - title: If it fails
      lead: These are failure routes the sources describe. None of them is a measured flight result.
      points:
        - label: Overload
          line: Corning gives a minimum average modulus of rupture of 94 MPa and says MACOR does not deform like a ductile material, so overload leads to fracture rather than yield.
        - label: Over-temperature
          line: Corning rates the material at 800 °C continuous and 1000 °C peak with no load; the datasheet prints no loaded data above those limits.
        - label: Strong acid
          line: In the Corning test, 5 % hydrochloric acid removes about 100 mg/cm2 in 24 h at 95 °C.
    - title: Handling and storage
      points:
        - label: Dust control
          line: Keep the container closed, store in a dry area, and use a dust suppressant or HEPA vacuum for crushed glass.
        - label: Machining
          line: Use a water-soluble coolant and carbide tools; no post-firing is needed after machining.
  why: MACOR is used where a machinable insulator must hold tight tolerances, stay stable at high temperature, and not outgas in vacuum. Corning says it can be cut with ordinary metalworking tools, that tolerances are very tight, and that no post-firing is required. Its matrix is a borosilicate glass with about 55 % fluorophlogopite mica, and the mica flakes are randomly oriented in the microstructure, which Corning names as the key to machinability.
  uses:
    - where: Vacuum equipment
      line: Corning says MACOR is used as an insulator, coil support and vacuum feed-through, sealed with a compatible sealing glass for a vacuum-tight joint.
    - where: Space Shuttle and spaceborne detector
      line: Corning says over 200 MACOR parts are on the Space Shuttle Orbiter, with retaining rings at hinge points, windows and doors, and that a NASA spaceborne gamma radiation detector uses large MACOR pieces. These are manufacturer claims.
    - where: Electrical and high-temperature insulation
      line: Precision Ceramics says MACOR is an excellent high-voltage insulator at high temperature, with a dielectric constant of 6.03 at 1 kHz from the Corning table.
  can_do:
    - label: Hold 800 °C
      value: 800 °C continuous
      benchmark: max_service_temp
      line: Corning rates continuous use at 800 °C and a 1000 °C peak with no load.
    - label: Stay dense
      value: 0 % porosity
      line: Corning gives zero porosity and says it is clean, with no outgassing when properly baked out.
    - label: Be machined
      value: very tight tolerances
      line: Corning says tolerances are very tight, with surface finish below 20 µin and a polished finish of 0.5 µin-AA.
  compare: MACOR is a machinable insulator, not a conductor. Its thermal conductivity is 1.46 W/m°C at 25 °C, far below the copper profile on this site, and its modulus of rupture is 94 MPa. Corning says its coefficient of expansion readily matches most metals and sealing glasses; the 9.3 ppm/K value is for 25 to 300 °C. Read the table rows as examples, not as a ranking, since they are different classes of material.
  compare_rows:
    - label: Density
      benchmark: density
    - label: Thermal conductivity
      benchmark: thermal_conductivity
    - label: Thermal expansion
      benchmark: cte
  handling:
    - 'Keep dust down: avoid breathing it, wash after handling, and use a HEPA vacuum or dust suppressant for crushed glass.'
    - Use a water-soluble coolant and carbide tools when machining.
    - Do not exceed 800 °C in continuous use, or 1000 °C peak with no load.
  good_for:
    - 'Machined insulators: very tight tolerances with no post-firing, per Corning.'
    - 'Vacuum parts: zero porosity and no outgassing when properly baked out, per Corning.'
    - 'High-temperature insulation: 800 °C continuous, 1000 °C peak with no load.'
  watch_out:
    - 'Strength is modest: 94 MPa modulus of rupture and 1.53 MPa m0.5 fracture toughness.'
    - Dielectric strength and resistivity differ by manufacturer; check the datasheet for the grade you buy.
    - Machining dust is an irritant.
    - The Space Shuttle and gamma-detector uses are manufacturer claims, not flight data.
  verdict: MACOR is a machinable glass-ceramic with zero porosity, 800 °C continuous and 1000 °C peak use, and very tight tolerances without post-firing. Its strength is modest, with 94 MPa modulus of rupture and 1.53 MPa m0.5 toughness, and its dielectric and resistivity figures vary by source. The space uses rest on manufacturer statements, and this profile has no supply shares, process steps or flight outgassing data.
  recipe:
    line: MACOR is a borosilicate glass matrix containing fluorophlogopite mica, with the mica flakes randomly oriented in the microstructure (Corning; Wikipedia). It is melted and crystallised as a glass-ceramic; no process step is given in the fetched sources.
    parts:
      - name: Silicon dioxide
        symbol: SiO2
        share_percent: 46
        role: Glass former and mica network
      - name: Magnesium oxide
        symbol: MgO
        share_percent: 17
        role: Mica cation
      - name: Aluminium oxide
        symbol: Al2O3
        share_percent: 16
        role: Mica and glass network
      - name: Potassium oxide
        symbol: K2O
        share_percent: 10
        role: Mica interlayer cation
      - name: Boron oxide
        symbol: B2O3
        share_percent: 7
        role: Borosilicate glass former
      - name: Fluorine
        symbol: F
        share_percent: 4
        role: Mica fluorine
  source: corning-macor-datasheet