Henry: Assuming that giant spiders are too hostile and dangerous to harvest silk from would entirely defeat my purpose. It is true that one of the biggest problems in harvesting spider silk on any large scale in the real world is that, unlike silkworms, the spiders are too aggressive with respect to each other: in defense of their own perceived territory, they'll attack (and sometimes eat) each other, so it's hard to keep large numbers of them together. Each spider produces a finite amount of silk thread, and you need a lot of (normal sized) spiders to produce even one bolt of cloth, but you can't keep the spiders together.
My character is a half elf, raised by his elven parent in a semi-remote forest that my DM and I have recently decided is home to a domesticated breed of giant spider. Two human kindgoms border the forest and take it in turns to try to conquer the elven forest, in part to gain control of this potentially valuable source of silk; it's not a major export for the elves, but no doubt the humans see gold shining every time they see the spider silk.
(Actually, that's literally true: like the golden orb spider in the real world, the giant spiders of the Thornwood produce a silk that has a gold colored tint to it.)
My character will be transplanting some of the spiders, probably to a small island, and setting himself up as a spider silk merchant on a small scale, well outside the area where the Thornwood elves trade. This is basically a plan for earning retirement income, not something that's going to have much of an effect on the economics of the adventuring game, but even so I'd like to have an idea of the number of spiders that might be needed, the area of land necessary to support that number of spiders, how many workers will be needed to harvest the silk, how many weavers needed to create cloth from the silk, etc. These variables are all interdependent, so I need to pick a starting point and work from there. I wanted to know if anyone else had done it before I reinvented the wheel for myself.
Anyway, having decided we want to establish this small scale industry for the Thornwood elves, I cannot very well address the problem by saying it won't work because the spiders are too aggressive.
Steveroo: Although I'd forgotten about spider silk being used as crosshairs for gun sights, I had read that somewhere before, so yes, I was incorrect to say that spider sillk had no commercial applications in the real world. However, what I had in mind when I said that was the mass production of bolts of silk cloth: the textile industry, not the manufacture of accessories for rifles. Sorry I misspoke.
I will not be maiming the spiders. If it proves to be necessary to drug them periodically in order to harvest silk, okay.
Kid Charlemagne: If you have any numbers on how spider silk production works in your campaign, I'd love to see them. For purposes of the game, I did not plan to treat spider silk as any different from the ordinary variety (though it should be stronger), though you might be able to advertise the stuff as superior on the basis of the source alone. Kind of how Ricardo Montalban used to advertise the Chrysler Cordoba as being uphostlered with "rich, Corinthian leather" although there's nothing about Corinthian leather that makes it better than any other sort.
Goobermunch: Yeah, I saw the Science of Superheroes program, and it's not technically difficult to extract 1000' or so of silk thread from one spider. The difficult part is doing that extraction from many thousands of spiders that have to be kept separated from each other when they're not strapped to the extraction table.
And I know about the spider gene being given to certain goats, in order to have them produce a silk enzyme in their milk; that looks promising for future applications in the creation of synthetically produced silk for the textile industry, but in a D&D fantasy world it's a bit harder to apply. I guess I could hypothesize the creation of an abberation, hybridizing the spider and goat in such a way as to replace the goat's normal hair with silk threads. But that would kind of change the image of the Thornwood elves from a group living in harmony with nature, and domesticating unusual creatures, to a bunch of insane, nature-twisting wizards.
There may be an alchemical alternative to this. Spiders have different sorts of spinnerettes, which secrete different liquids; different combinations of these liquids, in the air, form different types of silk line for the spider to use. Elven alchemists could find a way to extract small amounts of the liquid from each separate spinnerette reservoir, then use Metamorphose Liquid (a massively useful 2e spell that I have not seen in any 3e sourcebook) to replicate the stuff by the barrel. Tiny valves fitted to each barrel would duplicate the function of the natural spinnerettes and allow the liquids to combine in air to form silk thread.
It really seems much simpler to suppose that the elves found a way to keep this particular breed of spiders from killing each other off, and then just harvested the silk as it is naturally produced.
Umbran: As I said, I'm aware of why this isn't being done in the real world. And I realize that, barring some creative solution to those problems, using giant spiders is just going to make the real-world problems that much bigger. Since it's a fantasy game, we can imagine there might be ways in which these practical problems have been solved; my post was just asking for any existing references that make that assumption.
Yes, I still want to use giant spiders for this. Does it still sound like a great idea? Well, it never sounded like a great idea if by "great idea" you mean "something that will make silk a lot easier to get, or cheaper to make." This was something we wrote into the description of the Thornwood elves to make them different and more colorful, not masters of practical technology. I wasn't trying to introduce spider silk as an "improvement" on the product of the mulberry-munching silkworm. There are no silkworms in the Thornwood, and that group of elves has no direct trade with the producers of ordinary silk, but they did find a way to make the material with the resources available to them.
