In this timeline's equivalent of medieval level development, spider silk is dirt cheap, and cross-laminated sheets of spider silk are quite affordable.
Portia jumping spiders were domesticated hundreds of millennia ago, ballooning their number of neurons to several million. Consequently, they have many new cognitive abilities, such as transmitting and receiving instructions like a bee's waggle dance (but more efficiently using small rapid movements of their iridescent legs), recognizing faces (also like bees), and even limited self-awareness (though since some ants can pass the mirror test, it's clearly much less cognitively demanding than people usually think).
Spider silk has its disadvantages, like its elasticity and flammability in a setting where Greek fire and psychics able to shoot optical lasers are both decently common. But you could also use reflective materials and asbestos in addition.
Notably, many of spider silk's limitations seem like they can be ameliorated by binding cross-laminated layers of spider silk into sheets using resin.
The process of creating cross-laminated sheets of spider silk can be almost entirely done by the spiders, along with trained domesticated dwarf mammoths and crows. For instance, pre-stressing by having the dragline laid out between pegs so the ends can be pulled by birds to keep a layer taut until the resin has poured and dried.
I was imagining this cross-laminated material would likely replace metal and wood in a huge variety of contexts as armor and a structural material. However, I don't know enough about materials like this to predict where people would still want to use metal beyond obvious cases like weaponry (since I wouldn't expect this sort of resin composite to hold an edge) and cooking utensils. In much the same way, I don't know if there's any practical application where this wouldn't beat out wood.
So just how ubiquitous should this stuff be?
Would it be used for nearly everything like plastics are today?(or possibly even more so) Or would the ideal use cases be more limited than I initially thought?
This question considers medieval technology levels, but Earth in this the timeline is vastly more connected than our own. So you needn't be limited to the plants that medieval Europe had access to.
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