The reference glass of every visible-light optical lens system. BK7 (Schott trade name; equivalents at Hoya / Ohara / CDGM) is the canonical 'crown' glass — moderate refractive index (1.5168), low dispersion (Abbe number 64.2), excellent visible-band transmission (>99 percent at 400-1100 nm in clean stock), and exceptional homogeneity (the inhomogeneity through the bulk is below what shows up in a polarized-light test). The lens elements in every consumer camera, every binocular, every microscope objective, every telescope ocular are mostly BK7 or one of its close cousins (the F2 flint glass it pairs with in achromatic doublets, the SF11 or LASF heavy-flint for high-index applications). Worked by every optical-lens manufacturer worldwide. Buy from Edmund Optics or Thorlabs for lab / hobbyist optics, from Schott / Ohara directly for production-quantity blanks.
Borosilicate crown glass, composition typically 70 SiO2 / 10 B2O3 / 6 Na2O / 8 K2O / 6 BaO + minor (weight percent), produced by the platinum-stirred-melt continuous process for optical homogeneity. Density 2510 kg/m³. Refractive index nd 1.5168 (at 587.6 nm sodium-D), Abbe number Vd 64.17 (low dispersion — the 'crown' designation refers to glasses with Vd > 50). Transmittance > 90 percent at 350-2000 nm (with the longer-wavelength rolloff at 2700 nm). Coefficient of thermal expansion 7.1 × 10⁻⁶ /K. Knoop hardness 610. Chemical durability good against most environmental exposure but should be protected from prolonged contact with acids and alkali in cleaning. Optical-grade specifications include refractive index tolerance ± 1 × 10⁻⁴, Abbe-number tolerance ± 0.5 percent, internal homogeneity better than λ/4 over 100mm path, bubble class B0 (no bubbles > 0.1 mm in 100 cc), inclusion class B0. Polishes to lambda/10 surface flatness for premium optics; coatings (anti-reflection MgF2, broadband AR multi-layer) are applied as final step. Fabrication: blanks are saw-cut from boules / pressings, ground to near-finish on diamond cup wheels, fine-ground with progressively finer abrasives (15 µm to 3 µm), then pitch-polished with cerium oxide slurry to optical surface quality. Cuts and chips on impact at edges (the canonical optical-lens damage mode).
A spinning cloth pad at the arm's end, smeared with a variety of progressively less and less abrasive substances (from diamond slurry to jeweler's rouge to cerium oxide), was then lowered onto the face of the glass plate.
Principled BSDF defaults derived from the sphere transparent finish. Reasonable seed for Blender, Substance, Keyshot, Rhino — tune per material. Or grab the whole library at once: ForMaterials library →
# finish: transparent albedo #e0eef0 metallic 0.00 roughness 0.05 ior 1.50 transmission 1.00 clearcoat 0.00 sheen 0.00 anisotropic 0.00 thickness 1.00 attenuation_distance 0.60
{
"albedo": "#e0eef0",
"metallic": 0.0,
"roughness": 0.05,
"ior": 1.5,
"transmission": 1.0,
"clearcoat": 0.0,
"sheen": 0.0,
"anisotropic": 0.0,
"thickness": 1.0,
"attenuation_distance": 0.6
}
# Blender 4.x — Principled BSDF
# Optical Crown Glass (BK7) · finish: transparent
import bpy
mat = bpy.data.materials.new(name="mat_glass_optical_crown")
mat.use_nodes = True
bsdf = mat.node_tree.nodes["Principled BSDF"]
bsdf.inputs["Base Color"].default_value = (0.7454, 0.855, 0.8714, 1.0)
bsdf.inputs["Metallic"].default_value = 0.000
bsdf.inputs["Roughness"].default_value = 0.050
bsdf.inputs["IOR"].default_value = 1.500
bsdf.inputs["Transmission Weight"].default_value = 1.000
bsdf.inputs["Coat Weight"].default_value = 0.000
bsdf.inputs["Sheen Weight"].default_value = 0.000
bsdf.inputs["Anisotropic"].default_value = 0.000
# KeyShot 11+ — lux Python API, Generic material
# Optical Crown Glass (BK7) · finish: transparent
# Run from Window → Scripting Console
import lux
mat = lux.createMaterial(name="mat_glass_optical_crown", materialType="Generic")
mat.setProperty("diffuse", (224, 238, 240)) # 8-bit sRGB
mat.setProperty("metallic", 0.000)
mat.setProperty("roughness", 0.050)
mat.setProperty("indexOfRefraction", 1.500)
mat.setProperty("transparency", 1.000)
mat.setProperty("coatingWeight", 0.000)
{
"_format": "Substance Designer / Painter \u2014 pbrMetalRough constants",
"_about": "Optical Crown Glass (BK7) \u00b7 finish: transparent",
"baseColor": {
"r": 0.7454,
"g": 0.855,
"b": 0.8714
},
"metallic": 0.0,
"roughness": 0.05,
"ior": 1.5,
"opacity": 0.0,
"anisotropyLevel": 0.0,
"_notes": "Channels listed are the standard Substance pbrMetalRough output. Drop into a Uniform Color node per channel, or as the constant input on a layered stack."
}{
"asset": {
"version": "2.0",
"generator": "ForMatter"
},
"materials": [
{
"name": "mat_glass_optical_crown",
"pbrMetallicRoughness": {
"baseColorFactor": [
0.7454,
0.855,
0.8714,
1.0
],
"metallicFactor": 0.0,
"roughnessFactor": 0.05
},
"extensions": {
"KHR_materials_transmission": {
"transmissionFactor": 1.0
}
}
}
]
}# USD Preview Surface — UsdShade.MaterialLook prim attributes
# Optical Crown Glass (BK7) · finish: transparent
def Material "mat_glass_optical_crown" {
token outputs:surface.connect = </mat_glass_optical_crown/PreviewSurface.outputs:surface>
def Shader "PreviewSurface" {
uniform token info:id = "UsdPreviewSurface"
color3f inputs:diffuseColor = (0.7454, 0.855, 0.8714)
float inputs:metallic = 0.000
float inputs:roughness = 0.050
float inputs:ior = 1.500
float inputs:opacity = 0.000
float inputs:clearcoat = 0.000
token outputs:surface
}
}
Schott / Hoya optical-glass technical literature; ASTM C1503 optical-glass nomenclature.
House vocabulary — terms ForMatter uses with intent.
Materials and processes for people who design and make things.
A local-first library of materials, processes, applications, and finishes — equal weight, citable everywhere, with cost-over-volume curves, trade-off profiles, equipment-tier filters, and second-life paths layered onto the data so a student can move from "what is this" toward "what's actually buildable here, now, by me." Part of the renato.design ecosystem — sibling of Plenum, Specimen, Ingenue, gesture, graf, and the Renato Rhino plug-ins. Form and matter, inseparable.
Half of teaching materials is teaching how the material is made into the thing. The standard subscription library was always light on that half. The wedge here isn't better samples or a prettier interface — it's treating Process as a peer entity, not a footnote.
Conway's Material World on raw materials, Lefteri's Making It on processes, Forty's Concrete and Culture, Sparke's Design in Context, Bürdek's Design: History, Theory and Practice of Product Design, Schröpfer's Material Design on materials in architecture, Winchester's The Perfectionists on tolerance, Minshall's Your Life Is Manufactured on the global supply chain, von Busch's Making Trouble on material activism, Were's How Materials Matter, Hegger / Drexler / Zeumer's Basics Materials, Untracht and McCreight on metalsmithing, USDA Forest Products Lab on woods, GIA on gemstones, Schott / CoorsTek / Toray / Owens Corning datasheets, MakeItFrom for verifiable property numbers, ASM Handbook, ISO standards. Museum holdings draw from the Met, MAD, V&A, Smithsonian American Art Museum, Newark Museum of Art, British Museum, Heard Museum, Smithsonian NMAI, Eiteljorg Museum, Philadelphia Museum of Art, Cranbrook Art Museum, and Grand Rapids Art Museum — collection-record permalinks only, designer overview pages and exhibition listings excluded. Voice blocks now ride on every entry kind — material, process, application, and finish — and include Ruskin on iron, Anni Albers on twining, Greg Lynn on the shred-and-teeth NURBS lineage, Pugin on the metal that won't be hammered, Barthes / Yanagi / Benjamin channeled within their philosophy; Sparke, Bürdek, Forty, Conway, Schröpfer, Minshall, von Busch, Lefteri, Pat Pruitt, Mary Lee Hu, Tom Joyce, Albert Paley, and the rest of the contemporary makers quoted verbatim with citation. All cited.
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