Thank you everyone for your responses! I experimented with some old sweaters, with mixed results. Here are the processes, outcomes, and my next steps:
What I used:
Lansinoh 100% lanolin, dissolved in a small bowl of hot (boiling) water.
It was inexpensive and available locally.
Pre-washed three sweaters in a sink of tepid water, with Soak brand wash. Mixed dissolved lanolin into the water, soaked for 20 minutes, squeezed out the water, (did not rinse), rolled sweaters in towel, rack dried ~2days.
Sweater #1: Thrifted/vintage lambswool pullover. Started out scratchy and stiff, like a scouring pad - not much 'drape' or shape. After the soaking, it is *much* softer, and has more give. It is more of a bouncy/plush feeling than before. I may try another soak and see if it loosens up any more, but it's perfectly wearable as-is. It will never feel like cashmere, but anything is an improvement...
Sweater #2: Thrifted/vintage grandpa cardigan. 100% mystery wool (tag says 100% pure new wool, hand frame knitted, fully fashioned. No idea what that means). Had been dry cleaned after purchase, but had a weird smell and pokey threads. Water was disgustingly dirty after THREE washes. I washed it a fourth time, then added the lanolin. The weird smell was gone, threads were still pokey, but color seemed... brighter(?). I took a fabric shaver to it to try to help with the threads. I am not 100% satisfied with this, so I may try a lanolin based wash (like Unicorn or Euclan) and see if I get better results.
Sweater #3: Kuhl merino wool hoodie, in fun shade of Kermit-the-frog green, bought in 2003. This was my go-to layer under my Barbour jacket for YEARS until DH washed and dried it in a load of towels
I decided to try to re-block it to see if I could gain any size back. After the first soak, I didn't get MUCH size out of it, so I repeated the process, and this time used two caps of plant-based fabric softener that I had in the cabinet. I was able to regain MORE size with the fabric softener, but it still feels a bit smaller than it did when I used to wear it. Or maybe I am bigger (entirely possible...) The hoodie will work as an open layer under a jacket, but it is too snug to love it as a top layer. If I decide to order a lanolin wash, I may give re-blocking another shot, but it's fine for now.
I wish I had taken before/after pics, but I had already started soaking things by the time I thought to do it.
Anyway, hope this was helpful! Good luck if you try it, and let me know how it goes for you!
