First, the primary reason I wash thrifted yarn is I don't know where it came from. Sometimes there is a smoky smell, or a musty smell and those items are first in the wash bin. There's also a very distinct "thrift store item" smell which seems to permeate everything, be it yarn or clothing or furniture. Maybe they use a deodorizer for items before it goes to the floor...who knows?
At my local Value Village, they store the yarn and miscellaneous bits and bobs for crafting in a bin with half open packages of incontinence products. True story. Maybe they think the two go hand in hand? Old ladies need incontinence products and yarn...why not put them together? Hilarious.
Here's the bin:
I sort through the random skeins and bags, pick out the ones I think I'd use, usually in a multiple of 6 if I can (there are a LOT of novelty yarns which I don't tend to go for), then head to the counter. Once home, I take everything out and give it a good once over. I check for obvious stains or defects (I once found a skein that had been sliced by something through the label and a good inch in, the yarn was in short strings...I salvaged about a half skein), then I photograph each skein with its intact label (if it has one) so I can identify it after washing. If it has no label, no photo until after washing.
A typical haul looks like this:
Next, I get out my beautiful swift and start turning each skein into a hank. Please note my lovely assistant in the background who much prefers playing fetch over playing with yarn.
Once everything has been turned into a hank, it's ready for the wash basin.