That's a good question.
All I can come up with is this: I thoroughly soak my pieces in a very high quality fiber wash and rinse before blocking them, before seaming them. I allow each piece to soak in the fiber wash for about 15 minutes, then gently squeeze the water through them. Then repeat the same thing using the fiber rinse. So, I'm thinking...being so thoroughly clean, free of contaminants...perhaps that's why my wool coat didn't become smelly. Plus, the terry cloths that I plopped on top of them have never been used on the human body. No residue of human skin cells, or oils, etc. They are white, and I do not use them on anything but my knitting...like to block the seams and buttonbands, if needed, after the fact. IMO...Finishing is as important as the knitting itself.
Here's a write-up about the Unicorn (brand name) Fiber Wash and Fiber Rinse:
[COLOR=Navy]Created to protect and maintain the beauty of all fibers...from raw fleece and yarns, to your most cherished hand-knit possessions.[/COLOR][ul][COLOR=Navy]Gently deep cleans embedded dirt and staining[/COLOR][COLOR=Navy]Optimizes cleaning with less tangling and matting[/COLOR][COLOR=Navy]Softens scratchy yarns[/COLOR][COLOR=Navy]Removes odor-causing contaminants trapped within fiber[/COLOR][COLOR=Navy]Non-yellowing – No fillers[/COLOR][COLOR=Navy]Biodegradable – Earth Friendly[/COLOR][/ul]You'll notice it mentions: "removes odor-causing contaminants trapped within fiber".
You should see the wash water after soaking undyed natural cream Malabrigo sweater pieces! What you thought was cream yarn...renders enough filth to make you ill. I knit this Malabrigo sweater several years ago, and I was so shocked at the state of the wash water I just had to take photos of it!
Can you even believe it? I knit fast and furious, so my yarns didn't become
dirty from knitting something over two years.
This Unicorn Fiber Wash really does clean, without injuring the fibers. Right now, the Unicorn people seem to be offering free samples. You'll see the offer on their Home Page. Click here.
My wash water from the Nell (grey coat) also rendered dirt...although not as much dirt as that undyed natural Malabrigo! I have read that the dying process itself removes a lot of dirt. But only something like a quality fiber wash will remove the unseen contaminants and icky stuff from animal fiber yarns.
Another factor in behalf of using a quality fiber wash prior to seaming: if you left this 'unseen' dirt and filth in the yarn, it has to grind on your yarn. Wouldn't you think so? :think:
Here is the Malabrigo set:
Here is the matching cami-tank, before I had soaked it in the fiber wash and rinse.
It looks clean, doesn't it? But it also rendered just as much filth! Unbelievable.
I knit the jacket from beginning to end, then decided to knit a matching cami-tank to wear with it, using the same cable for the band, then seaming it into a band, then picking up stitches along one edge, and knitting down in-the-round, then knitting the ribbing. Then the i-cord straps.