Transparent wood

Also known as Optically transparent wood, Transparent wood composite, Delignified wood with polymer infiltration

Transparent wood is wood in which the light-absorbing lignin has been removed or chemically modified and the open porous structure is filled with a clear polymer, so that light can pass through. Laboratory samples reach up to about 90% total transmittance, but high haze, limits on thickness and unproven outdoor durability keep it at research and prototype stage.

Research and prototypesDemonstratedReviewed 21 Oct 2026
AI illustration · Illustrative scene, not a photograph of the specific device or experiment.

In plain language

Ordinary wood is not transparent, largely because lignin, a natural glue in the cell walls, absorbs visible light. Researchers treat the wood so that the lignin is removed or its light-absorbing groups are bleached. This leaves a porous scaffold made mainly of cellulose.

The scaffold is then filled with a clear polymer whose refractive index is matched to that of the wood, so light is scattered less at the boundaries inside the material. The result can be a sheet of wood that lets much of the light through and keeps its wood-like structure. Studies propose it for windows, light-transmitting buildings and transparent solar cell windows, but the material is still at laboratory and prototype stage.

Technical explanation

Lignin absorbs visible light through chromophores, which are conjugated chemical groups in its structure. Routes to remove or modify these groups include delignification with chemicals such as sodium chlorite or peracetic acid, and bleaching with hydrogen peroxide. One 2021 approach, reported by Physics Today, brushes hydrogen peroxide onto the surface and exposes it to ultraviolet light for as little as one hour to bleach the chromophores while keeping the lignin in place, which the report links to strength. The pores and the cellulose cell-wall network are then infiltrated with a polymer. The 2016 study by Li and colleagues used prepolymerised methyl methacrylate, chosen to be refractive-index-matched to the template, and reported that the hierarchical wood structure was preserved.

The main optical measures are total transmittance, which is the share of incident light that passes through, and haze, which the 2025 review by Pugliese and Malucelli describes as the relative amount of forward-scattered light, excluding ballistic light. Reported values depend strongly on thickness, wood species, anisotropy and polymer. Li and colleagues report transmittance as high as 85% with haze of 71%. Zhu and colleagues report total transmittance up to 90% for two highly anisotropic composite types. Across several composites in the review, thermal conductivity values of about 0.30 to 0.36 W per metre-kelvin are reported, and one 1.5 mm bleached bamboo sample reached 87% transmittance with 90% haze and tensile strength of about 118 MPa. Most of these figures come from different conditions, so they are hard to compare directly.

The review identifies several barriers. It states that there is no standardised protocol for measuring transmittance and haze, that optical quality often deteriorates when samples are scaled up to large-area or multi-millimetre specimens, and that long-term stability under humidity, ultraviolet light and heat is a critical bottleneck for outdoor use. It also notes that few studies have quantitatively examined how transmittance, haze and chromaticity change under these stresses. Lignin removal can involve toxic chemicals and by-products, which the review presents as a reason to consider lignin modification instead.

What the evidence says

Each statement is typed by the strength of its evidence and linked to the source that supports it.

Demonstrated Shown in a published experiment, test or shipping product.

Two types of highly anisotropic, highly transparent wood composites were reported, with total transmittance up to 90% and different optical and mechanical properties.

Sources: [2] · Abstract

Transparent wood made from a delignified nanoporous template filled with refractive-index-matched PMMA reached transmittance as high as 85% and haze of 71%.

Sources: [1] · Abstract

The same study reports that optical properties can be tuned by changing the cellulose volume fraction, and that wood and PMMA show a synergy in mechanical properties; the abstract gives no strength figures.

Sources: [1] · Abstract · medium confidence

Reported, unverified Stated by a company or team but not independently confirmed.

A 2021 Physics Today report describes brushing about 15 ml of hydrogen peroxide onto wood and exposing it to ultraviolet light for as little as one hour to remove light-absorbing lignin chromophores, followed by epoxy infiltration, giving transmittance up to 90% across 400 to 800 nm. The report shows a 1 mm thick balsa sample but does not clearly link that thickness to the 90% figure.

Sources: [3] · Main text · medium confidence

The same report gives a tensile strength of 20.6 MPa for lignin-modified wood and 0.4 MPa for wood with lignin fully removed by the conventional method.

Sources: [3] · Main text · medium confidence

A 2025 review reports that 1.5 mm bleached Moso bamboo, in a study by Wang and colleagues, reached 87% transmittance and 90% haze, with tensile strength of about 118 MPa and thermal conductivity of about 0.33 W per metre-kelvin.

Sources: [4] · Bamboo section · medium confidence

The 2025 review states that there is no standardised protocol for measuring transmittance and haze, and that optical quality often deteriorates when transparent wood is scaled up to large-area or multi-millimetre specimens.

Sources: [4] · Research gaps section · medium confidence

The 2025 review describes long-term stability under humidity, UV light and heat as a critical bottleneck for outdoor use, and notes that few studies have quantitatively examined how transmittance and haze change under these stresses.

Sources: [4] · Research gaps section · medium confidence

The Physics Today report describes the method as fast, scalable, low-cost and environmentally friendly, but gives no scale-up or production data.

Sources: [3] · Main text · medium confidence

Limitations and open problems

  • Haze is high in many reported samples. For example, the 2016 PMMA study reports 71%, and the 2025 review reports about 90% for some bamboo and balsa samples. High haze scatters light and blurs views through the material.
  • The 2025 review states that optical quality often deteriorates when samples are scaled up to large-area or multi-millimetre specimens, and treats glass-like clarity in thick, large-area structures as a goal still to be achieved.
  • The 2025 review describes long-term stability under UV light, humidity and heat as a critical bottleneck for outdoor use, and says few studies have quantitatively examined how transmittance and haze change under those conditions.
  • Lignin removal can involve toxic chemicals and by-products, according to the 2025 review.
  • There is no standard measurement protocol for transmittance and haze, so results from different studies are hard to compare.
  • The 2021 Physics Today report describes the method as fast, scalable and environmentally friendly, and gives no large-scale production or scale-up data. The only sample thickness it states is 1 mm, for a pictured balsa piece, and it does not clearly link that thickness to the 90% transmittance figure.

Possible future uses

Speculative

Ideas, not predictions. None of these has been demonstrated.

  • Light-transmitting buildings, which the 2016 authors name as a potential use for lightweight, low-cost transparent wood.
  • Transparent solar cell windows, which the 2016 authors also suggest.

Product concepts: Transparent wood window panel

Timeline

  1. 4 Mar 2016Li, Fu, Yu, Yan and Berglund publish optically transparent wood from a delignified nanoporous template filled with PMMA, reporting transmittance as high as 85% and haze of 71%. Sources: [1]
  2. 4 May 2016Zhu and colleagues publish highly anisotropic, highly transparent wood composites in Advanced Materials, reporting total transmittance up to 90%. Sources: [2]
  3. 1 Feb 2021Physics Today reports a faster method that uses hydrogen peroxide and ultraviolet light to bleach wood before epoxy infiltration. Sources: [3]
  4. 10 Dec 2025Pugliese and Malucelli publish a review of optical behaviour in transparent wood in Polymers, identifying microstructural anisotropy, refractive index matching and processing-induced defects as factors that determine transmittance and haze. Sources: [4]

Futures this could help bring about

AI illustration
How far away?

Windows and panels made of transparent wood

Engineering prototypes · 3 of 9 steps done

Glossary

Lignin
A natural polymer in wood cell walls that gives stiffness and colour, and absorbs much of the visible light that wood would otherwise pass.
Transmittance
The share of incident light that passes through a material, usually given as a percentage.
Haze
The share of transmitted light that is scattered forward rather than passing straight through, so that the material looks cloudy and blurs objects seen through it.
Refractive index matching
Choosing a filler with nearly the same refractive index as the host material, so that light is not bent and scattered at the boundary between them.

Sources

  1. peer reviewed paper
    Optically Transparent Wood from a Nanoporous Cellulosic Template: Combining Functional and Structural Performance
    Li, Fu, Yu et al.. Biomacromolecules (ACS Publications), 4 Mar 2016. DOI: 10.1021/acs.biomac.6b00145. Accessed 21 Oct 2026.
  2. peer reviewed paper
    Highly Anisotropic, Highly Transparent Wood Composites
    Zhu, Song, Li et al.. Advanced Materials (Wiley), 4 May 2016. DOI: 10.1002/adma.201600427. Accessed 21 Oct 2026.
  3. news
    A fast, scalable approach to making wood transparent
    R. Mark Wilson. Physics Today (AIP Publishing), 1 Feb 2021. Accessed 21 Oct 2026.
  4. review article
    Toward the Optimization of the Optical Behavior of Transparent Wood: Current State of the Art and Perspectives
    Diego Pugliese, Giulio Malucelli. Polymers (MDPI), 10 Dec 2025. DOI: 10.3390/polym17243276. Accessed 21 Oct 2026.
  5. other
    Transparent Wood
    KTH Royal Institute of Technology, Sept 2026. Accessed 21 Oct 2026.

Revision history

3 changes since this profile was created.

Changes on 21 Oct 2026
Published on owner instruction (content loop iteration 10)d8d21cd
Sources and claims re-checked against originalsfbb434c
Initial profile drafted from primary sources7e66249