Understanding your materials when you work with yarn is one of the cornerstones of being a textile artist.
I discovered this book (the first edition - it's all you really need, not the 2nd edition which is a lot more expensive) back when it first came out in the early, oh, 1980s?
The format appealed to me because the information was given in concise clear language and there were lots of diagrams/charts illustrating various points. The fact that it was then, and may still be now, a textbook for textile science classes and that the two authors were, at the time, teaching textile science at the U of Manitoba just made it all that much more appealing!
There are other textile science books. I even own some of them. But time and again I return to this one.
So when people offer opinions, especially when they are incorrect, this is the book I point them at. When I'm teaching I always give the title and authors to my students. And I consult it regularly.
There seems to be such an emphasis on someone's experience or opinion and a de-emphasis on actual science these days, textile science is not immune.
For the Olds master weaving class especially, the whole point is to steer students towards actual, factual, information, not my opinion or someone else's opinion, but facts.
The book has great charts which allow me to compare the characteristics of one fibre to another. My experience at spinning allows me to understand how the spinning of yarn from the fibres can be used to modify the behaviour of fibres in thread, then how to further modify them during weaving.
I have also learned as much as I can about the actual production of fibre - how animals are raised, plants are harvested and how each are prepared for spinning.
I know that sheep are not routinely killed for their fibre, but shorn. Some animals that are killed, either for meat or because they are ill may possibly have their hides shorn to harvest their fibre, but the whole point of sheep and other animals that produce fibre is not to kill them for their fibre but to keep them as a renewable resource - producing at least one crop a year. Shearing is not harmful and it is not traumatic when done by an experienced shearer. Most shearers can complete the job in a matter of minutes and then the sheep are free to return to the flock. There might be a nick at times, but I've had a hair dresser snip my ear or poke me with scissors and I was just fine afterwards, too.
There are ads for 'vegan' fibres, by which it is meant that the fibres do not come from animals. Fair enough. Cotton, linen, and other plant fibres can be lovely. I admire people who have the courage of their convictions. But by and large, and most especially small holdings of rare or 'exotic' sheep breeds are not mistreated. Domestic sheep pretty much must be shorn because they don't shed their fibres anymore and the burden of several years of grown can actually be harmful to their health.
My opinion is that I want to use fibres that will degrade back to dust, just like I'm going to one of these days. I prefer to not use synthetic fibres. I do still have some acrylic yarns in my stash, and I will use them. They might as well be put to use since they already exist. But I don't buy them and prefer to not use them.
But that is my personal line in the sand and I don't insist that everyone else follow me. When it is a moral issue, we each have to decide how to approach our textile practice and work accordingly.
However, I do strongly suggest that people find out facts, not react to a meme they saw on social media. Those memes are designed by media folk, they rely on emotional trigger words/images, and may not be the best thing to be paying attention to when facts are out there, readily available when you take the time to look for them.
When doing a web search, pay attention to who is sponsoring a web site. If the web site is paid for by the cotton council, they may not be telling the whole truth about bamboo, for example. I'm not saying bamboo is 100% wonderful - like every other fibre, it has issues!
It is because I think this information is so important that I included some fibre info in my book.
And listed A Guide to Textiles for Interior Designers in my bibliography.