The same way you get steel from candleberries, cotton acts as a source of instrumentum so you can pull iron -> bronze transmutation. Iron is easy to get too, just set up an iron golem farm, vanilla or TT will both work fine, pretty sure ender io is disabled though. For the cotton your best path is to craft it to string then the string to woven cotton, that will earn you 0.5 instrumentum per PHC cotton or one ingot of iron transmuted across. You'll build up a supply of bestia and humanus though as it produces those in waste at a 3:2:1 ratio of instrumentum:bestia:humanus.
At least that's what I assume they're doing, although if I am right then a tip for everyone thinking of the same thing. Crafting tables have 4 fabrico, so 2 instrumentum, 2 humanus after centrifuging. That gives you a ratio of 1 log to 1 instrumentum and with how easy and useful logs are you can even merge it with a charcoal/alumentum setup that purely takes in wood to output alumentum and instrumentum. No idea what you'd do with all the humanus though. Sadly no GT tool support in most crafting system so you're limited a bit more in efficiency but you can still get pretty good rates with a pure wood system.
Yeah, i was having an internal struggle: should i go the wood route with wooden shovels? or go cotton route ?
I didn't think about the crafting table, anyways it was a learning experience and now i know how to automate crop farming, even pam's harvestcraft crops works
It opens up a lot of paths.
Vitreus (crystal) is one of my hardest "commonly used" aspects to gather, but i see now that there is even a third option for it: centrifuging metallum, and it is a viable option now that i have a treefarm that can produce metallum, but i didn't want to bog down my iron production anymore so i went cotton route, mostly because i always wondered if i could automate pam's harvestcraft corps. Even the lamp of growth works with those modded crops, so it is almost fully supported. But at the same time: i don't want to depend on random mods to get by, it feels "exploitish" or "cheatish" in a way, i am supposed to be fine with just thaumcraft and vanilla minecraft to get all my vanilla TC aspects so i don't like using cotton for this because: in a way, it is cheating
I feel a bit bad about scanning non vanilla or TC / TC addon items, it "artificially inflates" my research points, i'm not supposed to have so much that i do and it lessens the TC experience.
But my counterargument is i don't want to be cruel to all the sheep out there as i try to avoid hurting animals and i was already doing a treefarm so it was the best option except for metallum centrifuging i guess.
What didn't work was using a golem with "use" core, it will get stuck on the first crop that you link it too, it will harvest that crop fine without needing to replant seeds, but ignores all the rest. That is what i tried first, the "use" golem method, now i know it isn't viable without bonemeal. Though as of writing, i'm using two harvest golems to cut down all the fully grown crops, two gather golems to collect:
1) Seeds for replanting and turning some into herba essentia which runs the lamp of growth
2) Cotton to craft it into strings then woven cotton which turns into 2 pannus and 1 fabrico
That fabrico is used to keep golems awake and the pannus is centrifuged into instrumentum and bestia, bestia is simply put into a void jar but the instrumentum is tubed into a thaumatorium to be processed into bronze nuggets which turns into bronze ingots which i haven't started dealing with yet, i'll macerate some and keep some for later
I'll get tons of copper, tin and bronze anyways!
I've been thinking about doing a blaze farm for some reason, i already have the blaze spawner in my wand focus but have yet started construction, i'll eventually start doing some sort of mob/animal entity farm though.