{
  "spore": "profile",
  "id": "balsa-wood",
  "spore_version": "0.2",
  "family": "wood",
  "name": "Balsa wood (Ochroma pyramidale)",
  "role": "Low-density natural wood for light cores in composites, model structures and light-aircraft panels",
  "category": "living",
  "type": "bio-grown-building-materials",
  "summary": "Balsa wood is the wood of the tree Ochroma pyramidale. Its dry wood density runs from 40 to 475 kg/m3 across the range quoted by Wikipedia, with about 160 kg/m3 typical. The High grade (200 to 400 kg/m3) listed by Spot Material has a tensile modulus of 5.5 to 6 GPa, a tensile strength of 16.3 to 40 MPa and a thermal conductivity of 0.9 to 1.2 W/mK. Its green moisture content is 200 to 400 per cent, so it is kiln dried before use (WoodSolutions).\n",
  "best_for": "Light cores in composites and model structures, where low density matters more than strength",
  "weakest_at": "Low toughness (up to 15 Nm as printed by WoodSolutions) and very high green moisture content that must be dried out",
  "identity": {
    "formula": "Wood of Ochroma pyramidale: cell walls of cellulose, hemicellulose and lignin, with air-filled cells",
    "designations": [],
    "source": "wikipedia-balsa",
    "where": "Taxonomy section: Ochroma pyramidale (Cav. ex Lam.) Urb.; sole member of genus Ochroma; family Malvaceae (Wikipedia, Balsa)"
  },
  "tags": {
    "environments": [],
    "stresses": [],
    "applications": [
      "structures"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Dry wood density, range",
      "value": 40,
      "value_high": 475,
      "bound": "range",
      "unit": "kg/m3",
      "scope": "material",
      "conditions": {
        "basis": "dry wood density range as printed, Ochroma pyramidale",
        "moisture": "not stated on the page"
      },
      "method": "Range printed in the Wikipedia article (the article cites Porter 2004, WoodSolutions and Borrega et al. 2015 for it)",
      "status": "ground",
      "source": "wikipedia-balsa",
      "where": "Wood density paragraph, density range (2.5 to 29.7 lb/cu ft also printed)",
      "source_detail": {
        "title": "Balsa (Wikipedia article)",
        "id": "Wikipedia, Balsa",
        "url": "https://en.wikipedia.org/wiki/Balsa",
        "kind": "web",
        "license": "CC BY-SA (Wikipedia)"
      }
    },
    {
      "benchmark": "density",
      "label": "Dry wood density, typical",
      "value": 160,
      "bound": "exact",
      "unit": "kg/m3",
      "scope": "material",
      "conditions": {
        "basis": "typical dry wood density, printed as around 160 kg/m3",
        "moisture": "not stated on the page"
      },
      "method": "Typical value printed in the Wikipedia article (same refs as the range)",
      "status": "ground",
      "source": "wikipedia-balsa",
      "where": "Wood density paragraph, typical value (10 lb/cu ft also printed)",
      "source_detail": {
        "title": "Balsa (Wikipedia article)",
        "id": "Wikipedia, Balsa",
        "url": "https://en.wikipedia.org/wiki/Balsa",
        "kind": "web",
        "license": "CC BY-SA (Wikipedia)"
      }
    },
    {
      "benchmark": "density",
      "label": "Commercial range, printed with the 160 value",
      "value": 120,
      "value_high": 220,
      "bound": "range",
      "unit": "kg/m3",
      "scope": "material",
      "conditions": {
        "basis": "density printed as 160 (120-220); the page gives the commercially preferred range as 120-160",
        "moisture": "moisture basis not stated on the page"
      },
      "method": "Printed on the WoodSolutions balsa page; the page prints the unit as kgm3, written here as kg/m3",
      "status": "ground",
      "source": "woodsolutions-balsa",
      "where": "Density row of the species property table",
      "source_detail": {
        "title": "WoodSolutions: Balsa (Ochroma pyramidale) species page",
        "id": "WoodSolutions, balsa",
        "url": "https://www.woodsolutions.com.au/wood-species/balsa",
        "kind": "web",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "density",
      "label": "Density per standard, seasoned",
      "value": 160,
      "bound": "exact",
      "unit": "kg/m3",
      "scope": "material",
      "conditions": {
        "basis": "density per standard, seasoned wood",
        "moisture": "moisture basis not stated; page lists the unseasoned value separately as 700 kg/m3"
      },
      "method": "Printed on the WoodSolutions balsa page under Density per Standard; unit printed as kgm3, written as kg/m3",
      "status": "ground",
      "source": "woodsolutions-balsa",
      "where": "Density per Standard row",
      "source_detail": {
        "title": "WoodSolutions: Balsa (Ochroma pyramidale) species page",
        "id": "WoodSolutions, balsa",
        "url": "https://www.woodsolutions.com.au/wood-species/balsa",
        "kind": "web",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "density",
      "label": "High grade density",
      "value": 200,
      "value_high": 400,
      "bound": "range",
      "unit": "kg/m3",
      "scope": "material",
      "conditions": {
        "grade": "High (200-400 kg/m3), as listed by Spot Material",
        "test": "not stated on the page"
      },
      "method": "Range printed on the Spot Material High grade page",
      "status": "ground",
      "source": "spotmaterial-balsa-high",
      "where": "Density row of the design properties table",
      "source_detail": {
        "title": "Spot Material: balsa, High grade (200-400 kg/m3) design properties",
        "id": "Spot Material balsa page, High grade",
        "url": "https://spotmaterial.com/material/balsa/high-200-400-kg-m3/",
        "kind": "database",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "specific_gravity",
      "label": "Specific gravity, light density class",
      "value": 0.1,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "density_class": "light",
        "basis": "density class as labelled on the page; unit not printed (dimensionless)"
      },
      "method": "Printed in the grade table of the 1958 Forest Products Journal article; no moisture or test basis given",
      "status": "ground",
      "source": "forestprod-balsa-1958",
      "where": "Grade table, Light row",
      "source_detail": {
        "title": "Properties and uses of balsa (Forest Products Journal, 1958)",
        "id": "Forest Products Journal 8(8):27A-30A, 1958",
        "url": "https://forestprod.org/knowledge-base/properties-and-uses-of-balsa",
        "year": 1958,
        "kind": "paper",
        "license": "as shown on the knowledge-base page"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Tensile modulus, High grade",
      "value": 5.5,
      "value_high": 6,
      "bound": "range",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "grade": "High (200-400 kg/m3), as listed by Spot Material",
        "test": "tensile, as printed; test standard not stated"
      },
      "method": "Range printed on the Spot Material High grade page; the page gives no separate data source",
      "status": "ground",
      "source": "spotmaterial-balsa-high",
      "where": "Design properties table, Tensile modulus row",
      "source_detail": {
        "title": "Spot Material: balsa, High grade (200-400 kg/m3) design properties",
        "id": "Spot Material balsa page, High grade",
        "url": "https://spotmaterial.com/material/balsa/high-200-400-kg-m3/",
        "kind": "database",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "ultimate_tensile_strength",
      "label": "Tensile strength, High grade",
      "value": 16.3,
      "value_high": 40,
      "bound": "range",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "grade": "High (200-400 kg/m3), as listed by Spot Material",
        "test": "tensile, as printed; test standard not stated"
      },
      "method": "Range printed on the Spot Material High grade page",
      "status": "ground",
      "source": "spotmaterial-balsa-high",
      "where": "Design properties table, Tensile strength row",
      "source_detail": {
        "title": "Spot Material: balsa, High grade (200-400 kg/m3) design properties",
        "id": "Spot Material balsa page, High grade",
        "url": "https://spotmaterial.com/material/balsa/high-200-400-kg-m3/",
        "kind": "database",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "flexural_modulus",
      "label": "Flexural modulus, High grade",
      "value": 5,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "grade": "High (200-400 kg/m3), as listed by Spot Material",
        "test": "not stated on the page"
      },
      "method": "Single value printed on the Spot Material High grade page",
      "status": "ground",
      "source": "spotmaterial-balsa-high",
      "where": "Design properties table, Flexural modulus row",
      "source_detail": {
        "title": "Spot Material: balsa, High grade (200-400 kg/m3) design properties",
        "id": "Spot Material balsa page, High grade",
        "url": "https://spotmaterial.com/material/balsa/high-200-400-kg-m3/",
        "kind": "database",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "flexural_strength",
      "label": "Modulus of rupture, High grade",
      "value": 28,
      "value_high": 70,
      "bound": "range",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "grade": "High (200-400 kg/m3), as listed by Spot Material",
        "test": "not stated on the page"
      },
      "method": "Range printed on the Spot Material High grade page. The same page prints a flexural strength of 350 MPa, which is left out (see gaps)",
      "status": "ground",
      "source": "spotmaterial-balsa-high",
      "where": "Design properties table, Modulus of rupture row",
      "source_detail": {
        "title": "Spot Material: balsa, High grade (200-400 kg/m3) design properties",
        "id": "Spot Material balsa page, High grade",
        "url": "https://spotmaterial.com/material/balsa/high-200-400-kg-m3/",
        "kind": "database",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "shear_modulus",
      "label": "Shear modulus, High grade",
      "value": 0.28,
      "value_high": 0.5,
      "bound": "range",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "grade": "High (200-400 kg/m3), as listed by Spot Material",
        "test": "not stated on the page"
      },
      "method": "Range printed on the Spot Material High grade page",
      "status": "ground",
      "source": "spotmaterial-balsa-high",
      "where": "Design properties table, Shear modulus row",
      "source_detail": {
        "title": "Spot Material: balsa, High grade (200-400 kg/m3) design properties",
        "id": "Spot Material balsa page, High grade",
        "url": "https://spotmaterial.com/material/balsa/high-200-400-kg-m3/",
        "kind": "database",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "compressive_strength",
      "label": "Compressive strength, High grade",
      "value": 20,
      "value_high": 40,
      "bound": "range",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "grade": "High (200-400 kg/m3), as listed by Spot Material",
        "direction": "not stated on the page"
      },
      "method": "Range printed on the Spot Material High grade page; compressive_strength is not in the canonical property file (see gaps)",
      "status": "ground",
      "source": "spotmaterial-balsa-high",
      "where": "Design properties table, Compressive strength row",
      "source_detail": {
        "title": "Spot Material: balsa, High grade (200-400 kg/m3) design properties",
        "id": "Spot Material balsa page, High grade",
        "url": "https://spotmaterial.com/material/balsa/high-200-400-kg-m3/",
        "kind": "database",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "label": "Thermal conductivity, High grade",
      "value": 0.9,
      "value_high": 1.2,
      "bound": "range",
      "unit": "W/mK",
      "scope": "material",
      "conditions": {
        "grade": "High (200-400 kg/m3), as listed by Spot Material",
        "temperature": "not stated on the page"
      },
      "method": "Range printed on the Spot Material High grade page",
      "status": "ground",
      "source": "spotmaterial-balsa-high",
      "where": "Design properties table, Thermal conductivity row",
      "source_detail": {
        "title": "Spot Material: balsa, High grade (200-400 kg/m3) design properties",
        "id": "Spot Material balsa page, High grade",
        "url": "https://spotmaterial.com/material/balsa/high-200-400-kg-m3/",
        "kind": "database",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "janka_hardness",
      "label": "Janka hardness, High grade",
      "value": 0.4,
      "value_high": 0.7,
      "bound": "range",
      "unit": "kN",
      "scope": "material",
      "conditions": {
        "grade": "High (200-400 kg/m3), as listed by Spot Material",
        "test": "not stated on the page"
      },
      "method": "Range printed on the Spot Material High grade page; janka_hardness is not in the canonical property file (see gaps)",
      "status": "ground",
      "source": "spotmaterial-balsa-high",
      "where": "Design properties table, Janka hardness row",
      "source_detail": {
        "title": "Spot Material: balsa, High grade (200-400 kg/m3) design properties",
        "id": "Spot Material balsa page, High grade",
        "url": "https://spotmaterial.com/material/balsa/high-200-400-kg-m3/",
        "kind": "database",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "janka_hardness",
      "label": "Janka hardness, as quoted from USDA",
      "value": 22,
      "value_high": 167,
      "bound": "range",
      "unit": "lbf",
      "scope": "material",
      "conditions": {
        "basis": "Janka hardness range as printed (98 to 743 N also printed); the article cites Wiepking and Doyle 1955 (USDA Forest Service)",
        "moisture": "not stated"
      },
      "method": "Range printed in the Wikipedia article, citing Wiepking and Doyle 1955",
      "status": "ground",
      "source": "wikipedia-balsa",
      "where": "Physical properties paragraph, Janka hardness (ref. 11)",
      "source_detail": {
        "title": "Balsa (Wikipedia article)",
        "id": "Wikipedia, Balsa",
        "url": "https://en.wikipedia.org/wiki/Balsa",
        "kind": "web",
        "license": "CC BY-SA (Wikipedia)"
      }
    },
    {
      "benchmark": "shrinkage_tangential",
      "label": "Tangential shrinkage",
      "value": 4.9,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "basis": "shrinkage as printed; the page does not say whether it is from green or dry to a given moisture",
        "rating": "page's shrinkage rating is unclear"
      },
      "method": "Printed on the WoodSolutions balsa page; shrinkage_tangential is not in the canonical property file (see gaps)",
      "status": "ground",
      "source": "woodsolutions-balsa",
      "where": "Shrinkage row, tangential",
      "source_detail": {
        "title": "WoodSolutions: Balsa (Ochroma pyramidale) species page",
        "id": "WoodSolutions, balsa",
        "url": "https://www.woodsolutions.com.au/wood-species/balsa",
        "kind": "web",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "shrinkage_radial",
      "label": "Radial shrinkage",
      "value": 1.8,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "basis": "shrinkage as printed; the page does not say whether it is from green or dry to a given moisture",
        "rating": "page's shrinkage rating is unclear"
      },
      "method": "Printed on the WoodSolutions balsa page; shrinkage_radial is not in the canonical property file (see gaps)",
      "status": "ground",
      "source": "woodsolutions-balsa",
      "where": "Shrinkage row, radial",
      "source_detail": {
        "title": "WoodSolutions: Balsa (Ochroma pyramidale) species page",
        "id": "WoodSolutions, balsa",
        "url": "https://www.woodsolutions.com.au/wood-species/balsa",
        "kind": "web",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "moisture_content_green",
      "label": "Green moisture content",
      "value": 200,
      "value_high": 400,
      "bound": "range",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "basis": "green (freshly cut) wood; moisture basis not stated, printed as 200-400%",
        "state": "green"
      },
      "method": "Printed on the WoodSolutions balsa page, which calls it very high and relevant to kiln drying; moisture_content_green is not in the canonical property file (see gaps)",
      "status": "ground",
      "source": "woodsolutions-balsa",
      "where": "Green moisture content row",
      "source_detail": {
        "title": "WoodSolutions: Balsa (Ochroma pyramidale) species page",
        "id": "WoodSolutions, balsa",
        "url": "https://www.woodsolutions.com.au/wood-species/balsa",
        "kind": "web",
        "license": "as shown on the page"
      }
    },
    {
      "benchmark": "toughness",
      "label": "Toughness, upper value",
      "value": 15,
      "bound": "upper",
      "unit": "Nm",
      "scope": "material",
      "conditions": {
        "basis": "printed as Low, up to 15 Nm for seasoned and unseasoned wood; the page gives no test standard",
        "state": "seasoned and unseasoned"
      },
      "method": "Printed on the WoodSolutions balsa page; toughness is not in the canonical property file (see gaps)",
      "status": "ground",
      "source": "woodsolutions-balsa",
      "where": "Toughness row",
      "source_detail": {
        "title": "WoodSolutions: Balsa (Ochroma pyramidale) species page",
        "id": "WoodSolutions, balsa",
        "url": "https://www.woodsolutions.com.au/wood-species/balsa",
        "kind": "web",
        "license": "as shown on the page"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Above ground, exposed to weather",
      "headline": "WoodSolutions prints above-ground durability ranges of 0-20 yrs (usually under 5), 21-40, 41-64 and more than 60 yrs.",
      "effect": "The page gives these durability ranges as classes. It does not say which exposure or test standard applies, and it does not name the class that holds balsa.",
      "rating": "unknown",
      "conditions": {
        "exposure": "above ground, per the WoodSolutions durability row",
        "basis": "durability classes as printed; no test standard stated"
      },
      "source": "woodsolutions-balsa",
      "where": "Above-ground durability row"
    },
    {
      "environment": "In ground, in contact with soil",
      "headline": "WoodSolutions prints in-ground durability ranges of 0-7, 7-15, 15-40 and more than 40 yrs.",
      "effect": "The page shows these as classes. It does not state the test standard or which class balsa belongs to.",
      "rating": "unknown",
      "conditions": {
        "exposure": "in ground, per the WoodSolutions durability row",
        "basis": "durability classes as printed; no test standard stated"
      },
      "source": "woodsolutions-balsa",
      "where": "In-ground durability row"
    },
    {
      "environment": "Green wood, freshly cut, before drying",
      "headline": "Green balsa holds 200-400% moisture, which the WoodSolutions page calls very high and relevant to kiln drying.",
      "effect": "Wood that holds this much water shrinks as it dries. The page prints tangential shrinkage of 4.90% and radial shrinkage of 1.80%, but it does not give the moisture range over which these apply.",
      "rating": "unknown",
      "conditions": {
        "state": "green",
        "basis": "moisture basis not stated on the page"
      },
      "source": "woodsolutions-balsa",
      "where": "Green moisture content row; Shrinkage rows"
    },
    {
      "environment": "Wood in general, moisture in the cell walls",
      "headline": "Wood retains 8-16% of the water in its cell walls, which softens it.",
      "effect": "The Wikipedia article on wood says water in the cell walls makes wood softer and more pliable. This is general wood, not measured on balsa.",
      "rating": "unknown",
      "conditions": {
        "basis": "general wood, not balsa-specific",
        "moisture": "8-16% of the water in the cell walls, as printed"
      },
      "source": "wikipedia-wood",
      "where": "Water content section"
    },
    {
      "environment": "Biological decay by rot-producing fungi",
      "headline": "Rot-producing fungi make wood weaker and leave colours that show the weakness.",
      "effect": "The Wikipedia article on wood says certain rot-producing fungi impart colours that are symptomatic of weakness. No decay rate for balsa is given in any source read in this run.",
      "rating": "unknown",
      "conditions": {
        "basis": "general wood, not balsa-specific"
      },
      "source": "wikipedia-wood",
      "where": "Colour section"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "OSHA's wood dust overview says wood dust becomes a potential health problem when wood particles from processes such as sanding and cutting become airborne, and that breathing these particles may cause allergic respiratory symptoms, mucosal and non-allergic respiratory symptoms, and cancer. The page also says the extent of these hazards and the associated wood types have not been clearly established, and it gives no numeric exposure limit. No balsa-specific hazard data were found.",
        "ghs": [],
        "source": "osha-wood-dust",
        "where": "Overview section, wood dust hazards"
      }
    ],
    "failure_risks": [
      {
        "mode": "Dimensional change as the wood dries from green",
        "trigger": "Drying from a green moisture content of 200-400%",
        "consequence": "Tangential shrinkage of 4.90% and radial shrinkage of 1.80% as printed by WoodSolutions; the page does not give the moisture range for these figures.",
        "severity": "moderate",
        "source": "woodsolutions-balsa",
        "where": "Shrinkage rows; Green moisture content row"
      },
      {
        "mode": "Low toughness",
        "trigger": "Impact or toughness loading of seasoned or unseasoned balsa",
        "consequence": "WoodSolutions prints toughness as Low, up to 15 Nm for both seasoned and unseasoned wood.",
        "severity": "moderate",
        "source": "woodsolutions-balsa",
        "where": "Toughness row"
      }
    ],
    "side_effects": [],
    "handling": [
      {
        "text": "WoodSolutions says the 200-400% green moisture content is very high and relevant to kiln drying, so green balsa must be dried before use.",
        "source": "woodsolutions-balsa",
        "where": "Green moisture content row and text"
      },
      {
        "text": "WoodSolutions prints tangential shrinkage of 4.90% and radial shrinkage of 1.80%, so dimensions change during drying.",
        "source": "woodsolutions-balsa",
        "where": "Shrinkage rows"
      }
    ],
    "mitigations": []
  },
  "uses": [
    {
      "application": "structures",
      "device": "Core panels for composites (wind turbine blades, surfboards, boat decks, table tennis rackets)",
      "example": "Wikipedia says more than 90% of the world's balsa wood volume is prepared into end-grain panels for the composites industry (no citation given in the article).",
      "source": "wikipedia-balsa",
      "where": "Uses section, composite core paragraph"
    },
    {
      "application": "structures",
      "device": "Lightweight structures and aircraft parts (model bridges, model buildings, model aircraft, full-size light aircraft such as the World War II de Havilland Mosquito)",
      "example": "Wikipedia lists balsa for model bridges, model buildings and model aircraft, and for components of full-size light aircraft, notably the World War II de Havilland Mosquito.",
      "source": "wikipedia-balsa",
      "where": "Common uses list, first and second items"
    },
    {
      "application": "structures",
      "device": "Core stock for doors, boat hulls, aircraft panels, wall or partition insulation and buoyant marine articles",
      "example": "The 1958 Forest Products Journal article lists balsa core stock for doors, boat hulls, aircraft panels, wall or partition insulation, and buoyant marine articles.",
      "source": "forestprod-balsa-1958",
      "where": "Uses paragraph"
    }
  ],
  "supply": [
    {
      "subject": "Balsa wood, commercial supply",
      "abundance": "Wikipedia gives two Ecuador shares for commercial balsa that disagree: 95% or more (Introduction) and 70% or more (Cultivation section). About 60% of balsa is plantation grown in densely packed patches (Cultivation). The article gives no year for these shares, and we found no second source for them.",
      "producers": [],
      "critical_lists": [],
      "recycling": "Not found in any source we hold.",
      "substitutes": [],
      "source": "wikipedia-balsa",
      "where": "Introduction; Cultivation section"
    },
    {
      "subject": "Balsa wood, plantation harvest",
      "abundance": "Wikipedia says trees are harvested after six to ten years of growth in Ecuador, and at four to five years of age in Papua New Guinea. Plantations hold about 1000 trees per hectare (400 per acre), against two to three per hectare in nature.",
      "producers": [],
      "critical_lists": [],
      "recycling": "Not found in any source we hold.",
      "substitutes": [],
      "source": "wikipedia-balsa",
      "where": "Cultivation section"
    },
    {
      "subject": "Balsa wood, export leader",
      "abundance": "Argus Media quotes the Global Development Policy Center of Boston University that Ecuador is the world's largest exporter of balsa wood. The article gives no production share and no plantation share.",
      "producers": [],
      "critical_lists": [],
      "recycling": "Not found in any source we hold.",
      "substitutes": [],
      "source": "argus-ecuador-balsa",
      "where": "Article body, sentence citing the Global Development Policy Center of Boston University"
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "Properties and uses of balsa (Forest Products Journal, 1958, 8(8):27A-30A)",
      "type": "paper",
      "url": "https://forestprod.org/knowledge-base/properties-and-uses-of-balsa",
      "year": 1958
    },
    {
      "title": "Mechanics of balsa (Ochroma pyramidale) wood, Borrega and Gibson, Mechanics of Materials 84 (2015), abstract page",
      "type": "paper",
      "url": "https://dspace.mit.edu/handle/1721.1/108580",
      "year": 2015
    },
    {
      "title": "Spot Material: Balsa, High grade (200-400 kg/m3) design properties",
      "type": "database",
      "url": "https://spotmaterial.com/material/balsa/high-200-400-kg-m3/"
    },
    {
      "title": "OSHA: Wood dust overview page",
      "type": "report",
      "url": "https://www.osha.gov/wood-dust"
    },
    {
      "title": "Argus Media: Ecuador balsa wood exports for wind turbines decline (article dated 13/07/22 as printed)",
      "type": "report",
      "url": "https://www.argusmedia.com/en/news/2350426-ecuador-balsa-wood-exports-for-wind-turbines-decline"
    }
  ],
  "gaps": [
    "Borrega and Gibson 2015 full text not read: the PDF download returned an HTML page, not a PDF. No modulus or strength value from the paper is used; only the abstract's density range (roughly 60 to 380 kg/m3) and its linear-in-density statement are cited.",
    "No balsa-specific chemical composition found. The recipe uses general wood composition from the Wikipedia Wood article (cellulose, hemicellulose, lignin).",
    "One hazard entry added from the OSHA wood dust overview (osha-wood-dust). That page is general to wood dust, gives no numeric exposure limit and does not mention skin effects. No balsa-specific hazard data found; the two NIOSH pages tried returned HTTP 404.",
    "No standard designation code (UNS, EN, ASTM, DIN, JIS) found for balsa in the pages read. designations left out.",
    "No supply share with a year found. The two Ecuador shares in Wikipedia (95% or more and 70% or more) conflict and are both printed. The MDPI paper (HTTP 403) and the EIA PDF (binary, unreadable) could not be read. The Argus article gives no share, only that Ecuador is the largest exporter.",
    "No critical-mineral list applies to balsa; USGS and EU lists were not checked for a wood.",
    "No ageing or durability test standard found. The durability ranges on WoodSolutions are classes without test conditions.",
    "Spot Material flexural strength of 350 MPa not used: it lies far outside the same page's modulus of rupture of 28-70 MPa, and it is treated as a typo.",
    "Spot Material Poisson's ratio of 0.23-0.66 not used: the upper value is above 0.5, the limit for isotropic materials, and the page gives no explanation.",
    "Forest Products Journal light-class modulus of rupture printed as –1,375 psi, with a dash that may be a print artifact. Not used.",
    "WoodSolutions MOR, MOE, compression, hardness and stress-grade figures have no unit printed or are grade codes. Not used.",
    "Spot Material temperature range of -200 to 150 °C and its cost, embodied energy and carbon footprint are printed without basis or are not canonical properties. Not used.",
    "Non-canonical property names used (not in spores/property-canon.yaml): specific_gravity, compressive_strength, janka_hardness, shrinkage_tangential, shrinkage_radial, moisture_content_green, toughness.",
    "Test standard, moisture basis and test conditions are not stated for most values. Each property's conditions say so.",
    "No images sourced in this run. media left empty."
  ],
  "story": {
    "why": "Balsa, the wood of Ochroma pyramidale, is valued for its low density. Wikipedia gives a dry wood density range of 40 to 475 kg/m3, with about 160 kg/m3 typical. The High grade on Spot Material is 200 to 400 kg/m3. The 1958 Forest Products Journal article and Wikipedia both list composite cores, model structures and light-aircraft parts as its main uses. Its low density is the reason for these uses, and its low toughness and high moisture are the reasons it needs careful handling.",
    "uses": [
      {
        "where": "Composite cores",
        "line": "Wikipedia says more than 90% of the world's balsa wood volume is prepared into end-grain panels for the composites industry. The article lists wind turbine blades, surfboards and boat decks among the composite uses."
      },
      {
        "where": "Model and light-aircraft structures",
        "line": "Wikipedia lists balsa for model bridges, model buildings and model aircraft, and for components of full-size light aircraft, notably the World War II de Havilland Mosquito."
      },
      {
        "where": "Core stock and buoyant articles",
        "line": "The 1958 Forest Products Journal article lists core stock for doors, boat hulls, aircraft panels, wall or partition insulation, and buoyant marine articles."
      }
    ],
    "can_do": [
      {
        "label": "Low density",
        "line": "Wikipedia prints a typical dry wood density of 160 kg/m3, and WoodSolutions prints 160 kg/m3 for seasoned wood per standard. The printed range runs from 40 to 475 kg/m3.",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Strength in bending, High grade",
        "line": "Spot Material prints a modulus of rupture of 28 to 70 MPa for the High grade (200 to 400 kg/m3). The same page prints a flexural strength of 350 MPa, which we did not use because it does not match its own range.",
        "benchmark": "flexural_strength",
        "scope": "material"
      },
      {
        "label": "Heat conduction, High grade",
        "line": "Spot Material prints a thermal conductivity of 0.9 to 1.2 W/mK for the High grade and labels balsa a thermal insulator.",
        "benchmark": "thermal_conductivity",
        "scope": "material"
      }
    ],
    "compare": "Balsa is a natural wood, so its figures depend on the density class and the grade. For the High grade, Spot Material prints a density of 200 to 400 kg/m3, a modulus of rupture of 28 to 70 MPa and a thermal conductivity of 0.9 to 1.2 W/mK. The 1958 article and WoodSolutions give figures for other density classes, but they do not print test conditions. The table compares density, bending strength and thermal conductivity, the three figures that the sources print on the same basis.",
    "compare_rows": [
      {
        "label": "Density, High grade",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Bending strength, High grade",
        "benchmark": "flexural_strength",
        "scope": "material"
      },
      {
        "label": "Thermal conductivity, High grade",
        "benchmark": "thermal_conductivity",
        "scope": "material"
      }
    ],
    "handling": [
      "Balsa is dried before use. WoodSolutions prints a green moisture content of 200-400% and relates it to kiln drying.",
      "Dimensions change as the wood dries. WoodSolutions prints tangential shrinkage of 4.90% and radial shrinkage of 1.80%.",
      "Toughness is low, up to 15 Nm as printed by WoodSolutions, so avoid impact loads that the wood cannot absorb."
    ],
    "good_for": [
      "Low-density cores. Wikipedia says most balsa volume goes into end-grain composite panels.",
      "Model and light-aircraft structures, as listed by Wikipedia and the 1958 Forest Products Journal article."
    ],
    "watch_out": [
      "Green moisture of 200-400% means the wood must be dried, and dimensions change as it dries (WoodSolutions).",
      "Toughness is low, up to 15 Nm as printed by WoodSolutions.",
      "Supply: Wikipedia gives two Ecuador shares that disagree (95% or more and 70% or more)."
    ],
    "verdict": "Balsa is a low-density natural wood with a broad range of printed figures. The values are useful for choosing a density class, but the sources read here do not give test conditions for most of them, so check the grade before design use.",
    "recipe": {
      "line": "Balsa is the wood of a tree (Ochroma pyramidale), so it has no single chemical formula. Its cell walls are built from cellulose microfibrils, hemicellulose and lignin, as described for wood in general in the Wikipedia Wood article.",
      "parts": [
        {
          "name": "Cellulose",
          "role": "Microfibrils that make up the cell wall (Wikipedia, Wood)."
        },
        {
          "name": "Hemicellulose",
          "role": "The matrix in which the cellulose microfibrils sit, impregnated with lignin (Wikipedia, Wood)."
        },
        {
          "name": "Lignin",
          "role": "Impregnates the hemicellulose matrix (Wikipedia, Wood)."
        },
        {
          "name": "Water",
          "role": "Wood retains this water, which makes it softer and more pliable (Wikipedia, Wood)."
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "No hazard classification for balsa wood was found in any source read in this run.",
        "points": [
          {
            "label": "Dust",
            "line": "OSHA's wood dust overview says breathing wood particles from sanding and cutting may cause respiratory symptoms and cancer, but the extent of the hazard is not clearly established. No balsa-specific dust data was found, and the two NIOSH pages we tried returned errors."
          }
        ]
      },
      {
        "title": "Handling and drying",
        "lead": "Balsa is not used green. WoodSolutions treats the moisture level as relevant to kiln drying.",
        "points": [
          {
            "label": "Green moisture",
            "line": "WoodSolutions prints a green moisture content of 200-400% and calls it very high."
          },
          {
            "label": "Shrinkage",
            "line": "Tangential shrinkage is 4.90% and radial shrinkage is 1.80%, as printed. The page does not give the moisture range for these figures."
          },
          {
            "label": "Toughness",
            "line": "WoodSolutions prints toughness as Low, up to 15 Nm, for both seasoned and unseasoned wood."
          }
        ]
      }
    ]
  },
  "updated": "2026-11-01",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 19,
    "unreachable": 2,
    "caveats": 3,
    "note": "Read by an AI assistant on 2026-11-01 from four pages named in the brief plus WoodSolutions and the Wikipedia Wood article. 26 values as printed. The MIT PDF and two NIOSH pages could not be read."
  },
  "sources": {
    "forestprod-balsa-1958": {
      "title": "Properties and uses of balsa (Forest Products Journal, 1958)",
      "id": "Forest Products Journal 8(8):27A-30A, 1958",
      "url": "https://forestprod.org/knowledge-base/properties-and-uses-of-balsa",
      "year": 1958,
      "kind": "paper",
      "license": "as shown on the knowledge-base page"
    },
    "spotmaterial-balsa-high": {
      "title": "Spot Material: balsa, High grade (200-400 kg/m3) design properties",
      "id": "Spot Material balsa page, High grade",
      "url": "https://spotmaterial.com/material/balsa/high-200-400-kg-m3/",
      "kind": "database",
      "license": "as shown on the page"
    },
    "wikipedia-balsa": {
      "title": "Balsa (Wikipedia article)",
      "id": "Wikipedia, Balsa",
      "url": "https://en.wikipedia.org/wiki/Balsa",
      "kind": "web",
      "license": "CC BY-SA (Wikipedia)"
    },
    "woodsolutions-balsa": {
      "title": "WoodSolutions: Balsa (Ochroma pyramidale) species page",
      "id": "WoodSolutions, balsa",
      "url": "https://www.woodsolutions.com.au/wood-species/balsa",
      "kind": "web",
      "license": "as shown on the page"
    },
    "mit-borrega-gibson-2015": {
      "title": "Mechanics of balsa (Ochroma pyramidale) wood",
      "id": "doi:10.1016/j.mechmat.2015.01.014 (Mechanics of Materials 84, pp. 75-90)",
      "url": "https://dspace.mit.edu/handle/1721.1/108580",
      "year": 2015,
      "kind": "paper",
      "license": "MIT DSpace record; full-text PDF not opened"
    },
    "wikipedia-wood": {
      "title": "Wood (Wikipedia article)",
      "id": "Wikipedia, Wood",
      "url": "https://en.wikipedia.org/wiki/Wood",
      "kind": "web",
      "license": "CC BY-SA (Wikipedia)"
    },
    "osha-wood-dust": {
      "title": "OSHA: Wood dust overview page",
      "id": "OSHA wood dust overview",
      "url": "https://www.osha.gov/wood-dust",
      "kind": "web",
      "license": "as shown on the page"
    },
    "argus-ecuador-balsa": {
      "title": "Argus Media: Ecuador balsa wood exports for wind turbines decline",
      "id": "Argus Media news article, dated 13/07/22 as printed",
      "url": "https://www.argusmedia.com/en/news/2350426-ecuador-balsa-wood-exports-for-wind-turbines-decline",
      "kind": "web",
      "license": "as shown on the page"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/balsa-wood/"
}