The clear plastic of every CD jewel case, every disposable cutlery set, every model-shop styrene sheet, every Petri dish, every plastic-window in a packaging box. General-purpose polystyrene (GPPS — the 'crystal' designation refers to optical clarity, not crystallinity) is one of the oldest commodity thermoplastics, in production since the 1930s. Brittle (snaps cleanly with a fingernail), perfectly clear, easy to mold, cheap, and the model-makers' favorite as 0.020-0.060 inch flat sheet stock that cuts with a knife and welds with solvent (MEK, dichloromethane). The high-impact variant (HIPS — high-impact polystyrene) adds a rubber phase that reduces clarity but raises impact strength; it's the white opaque sheet used in disposable food containers and refrigerator interiors. Buy from McMaster, Curbell Plastics for sheet stock, from Evergreen Scale Models for model-grade.
Thermoplastic amorphous polymer, structural unit -[CH(C6H5)-CH2]n-, glass transition Tg 100 °C. Density 1040 kg/m³. Tensile strength 35-55 MPa. Tensile modulus 2.7-3.5 GPa. Elongation at break 1-3 percent (very brittle — snaps without yield). Heat-deflection temperature 70-90 °C. Optically clear in unpigmented crystal form (visible-light transmission > 90 percent at typical 1mm thickness). Refractive index 1.59 (high for a commodity plastic, contributing to the 'glassy' look). Easy to inject (low melt viscosity, no shrinkage problems), easy to extrude into sheet and film, easy to thermoform, easy to solvent-weld with MEK / dichloromethane / Tamiya cement (the model-shop adhesive). High-impact polystyrene (HIPS) is the styrene-butadiene blend with 5-10 percent polybutadiene rubber dispersed as discrete phase; the rubber takes impact load and prevents brittle failure, at the cost of optical clarity (HIPS is opaque white). Resin identification code 6 (PS), not commonly recycled (RIC 6 is on most municipal streams' do-not-collect list); foam polystyrene (EPS, XPS — the 'styrofoam' heritage) recycling depends on regional facilities.
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 #e8f0f4 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": "#e8f0f4",
"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
# Polystyrene (GPPS, General-Purpose / Crystal) · finish: transparent
import bpy
mat = bpy.data.materials.new(name="mat_polystyrene_crystal")
mat.use_nodes = True
bsdf = mat.node_tree.nodes["Principled BSDF"]
bsdf.inputs["Base Color"].default_value = (0.807, 0.8714, 0.9047, 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
# Polystyrene (GPPS, General-Purpose / Crystal) · finish: transparent
# Run from Window → Scripting Console
import lux
mat = lux.createMaterial(name="mat_polystyrene_crystal", materialType="Generic")
mat.setProperty("diffuse", (232, 240, 244)) # 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": "Polystyrene (GPPS, General-Purpose / Crystal) \u00b7 finish: transparent",
"baseColor": {
"r": 0.807,
"g": 0.8714,
"b": 0.9047
},
"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_polystyrene_crystal",
"pbrMetallicRoughness": {
"baseColorFactor": [
0.807,
0.8714,
0.9047,
1.0
],
"metallicFactor": 0.0,
"roughnessFactor": 0.05
},
"extensions": {
"KHR_materials_transmission": {
"transmissionFactor": 1.0
}
}
}
]
}# USD Preview Surface — UsdShade.MaterialLook prim attributes
# Polystyrene (GPPS, General-Purpose / Crystal) · finish: transparent
def Material "mat_polystyrene_crystal" {
token outputs:surface.connect = </mat_polystyrene_crystal/PreviewSurface.outputs:surface>
def Shader "PreviewSurface" {
uniform token info:id = "UsdPreviewSurface"
color3f inputs:diffuseColor = (0.807, 0.8714, 0.9047)
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
}
}
Crystal polystyrene — clear, brittle, the disposable-cup material in cast sheet form. Mills cleanly but cracks under stress; small tools and shallow passes. Often used for short-run model-shop prototypes that don't need toughness.
Onsrud Cutter plastic feeds & speeds (PS / GPPS table); INEOS Styrolution polystyrene sheet-machining notes.
→ try this material in swarfSPI / PLASTICS recycling guide (RIC 6); INEOS Styrolution polystyrene technical literature.
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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