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Comment by larschdk | Hacker News Reader

I wish it had a less click-baity name than "transparent wood". It's wood with the lignin replaced with resin through a chemical process. Of course things can be be transparent if you replace them with something else, but then they are no longer wood if you remove the wood! It's not the the wood that is transparent, it's the resin! Dammit.

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Me too. It's even worse when they talk about how the "wood" is 10 times tougher than glass.

No, it's not the wood that's tougher -- it's the epoxy resin it's been filled with that's tougher, right?

Edit: So basically it sounds like the wood matrix is a way to add tensile strength to epoxy to make it more shatter-resistant when it's in thin sheets. I guess it's tricky semantics whether the main material should be referred to as epoxy/resin or as wood, when it's their combination.

And it seems like we have competing precedents: we refer to "carbon fiber" (the wood in this comparison) rather than the resin, but we talk about buildings made of "concrete" (the epoxy resin by analogy) rather than the rebar steel within.

Thanks to the comments below for helping to explain.

Well no, otherwise they would just use sheets of resin.

> it's the epoxy resin it's been filled with that's tougher, right?

Your comment seems to suggest that the cellulose left after removing the lignin from the wood isn't playing any role. The wood really is playing an integral role.

It's the epoxy reinforced with the cellulose remaining after lignin removal that's tougher. Just a block of cured epoxy resin isn't going to be tougher than glass.

It's a similar case with "carbon fiber" items. If you just wrapped a pressure vessel with carbon fiber, it really wouldn't help much. It's the carbon fiber reinforced resin that's strong. That tennis racket wouldn't work very well with just carbon fiber or just epoxy resin.

Yeah, same goes for reinforced concrete. Just concrete or just rebar isn't going to work nearly as well. It's the two combined that provide the powerful combination of compressive strength and tensile strength. This is the whole rationale behind composite materials: combining different materials with different properties to obtain a gestalt material.

> Just a block of cured epoxy resin isn't going to be tougher than glass.

I wouldn't be so sure -- toughness has a specific meaning (energy before fracturing), and polymers are generally going to be tougher than glass.

http://www-materials.eng.cam.ac.uk/mpsite/interactive_charts...

I haven't dug into it, but note how the article mixes up these terms to make it sound better:

> transparent wood came out around three times stronger than transparent plastics like Plexiglass and about 10 times tougher than glass.

If you plot that on those graphs it doesn't put it anywhere remarkable.

edit: This is like trying to sell an electric bike by saying that it's three times faster than walking and 1/10 the price of a car -- ok, but how does it compare to a pedal bike? It's much more obvious when you do it with words that most people understand intuitively.

Even then, the wood is still stronger. If you research densified wood, it's a similar process that uses a heated chemical bath to remove the lignin but then instead of replacing it with resin, they compress the wood at temperature. It provides strengths comparable to steel by weight without adding new material to it.

Some quick numbers from a recent study:

Transparent wood tensile strength - 171 MPa

Basswood tensile strength - 2.4 MPa

PMMA plastic - 75 MPa

*Edit - Non-transparent densified wood - 398 MPa

https://www.sciencedirect.com/science/article/abs/pii/S13598... https://designerdata.nl/materials/plastics/thermo-plastics/p... https://www.matweb.com/search/datasheet.aspx?matguid=1775e21... https://pubmed.ncbi.nlm.nih.gov/35807412/

Basswood is about the worst wood you could choose. You can damage it with your hands.

They needed something porous and compressible, so it sounds like a great choice.

I think the key word here, somewhat buried in the article, is "sustainability". If you can convince someone that what you're selling is really wood, then you get your brownie points for being green. Epoxy resin doesn't sound quite so sexy and sustainable in a planet-conscious marketplace.

Well, the names things have should at least give you a hint about what they are. "Transparent wood" doesn't tell you everything about what the material is, but it does tell you part of where it comes from (trees) and it tells you that it's transparent. That's enough for a person to have a vague notion of what it looks like without having ever seen it, even if they still don't know what it is. Conversely, if we were to refer to it by a more precise description such as "structure of cellulose tubules held together by a polymer and disposed in an axially optically transparent manner", that would tell you more about what the material is made of, but practically nothing about what it looks like and why it's interesting.

IIRC it's not replacing the lignin -- the lignin are the tubes that give wood rigidity. This process removes what is inside the lignin with resin.

The tubes are called xylem and phloem. Lignin is one biopolymer that is used in their construction, but it's not the only one (cellulose is even more important) - and you shouldn't confuse the building material with the structure.

Also, the article specifically says that these processes will usually remove the lignin to make the result transparent.

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