When I started working with certain primitive breeds of sheep wool, I quickly realized that traditional scouring (using hot water & detergent) wasn’t always the best method for cleaning certain fleeces. Icelandic is a good example. Sometimes primitive-type fleeces warrant full-scale scouring and sometimes, they only require cold washing.
Note: While every breed of wool is different, every fleece is also different. One Icelandic fleece may have plenty of lanolin, while others may be dryer. Genetics, diet, stress, and weather all play a factor in fleece production.
I purchased an Icelandic ram fleece that happened to be really dry (very little lanolin) and when I scoured the first sample, I decided that the wool was too dry after the scouring. It almost felt crunchy. So, the second time around, I decided to cold wash the sample. This removed the dirt and suint (sweat salts) but left enough lanolin on the wool to keep it from completely drying out. (Just a side note here: I always leave some lanolin in every fleece that I wash; I’m never too heavy-handed with the soap). When I was ready to spin the cold-washed wool, it spun up nicely and the finished yarn felt much better than the scoured sample.
So, how do we determine when a fleece should be cold washed only or scoured?
Like the Icelandic fleece mentioned above, if the fleece is especially dry (low lanolin), that fleece might be a good candidate for cold washing only*.
Another time is when you’re wanting to spin “in the grease”, but the fleece is too dirty to spin in its raw state. Dirt mixed with lanolin (even small amounts) can gunk up our spinning wheel orifices and leave residue on our person, making a big mess. Cold washing remedies this while allowing us to spin with the lanolin left in the fleece.
Short staple-length fleeces are often good candidates for cold washing because the lanolin can help hold the short fibers together while spinning. Exotic fibers like dog fur, cat fur, and rabbit fur are other examples. (While dogs, cats, rabbits, etc. don’t have lanolin in their fibers, they do contain natural oils that help hold the fibers together when spinning).
When I want to store a fleece, but I don’t necessarily want to scour it yet, I often use cold washing. This allows me to remove dirt and suint from the fleece before storage.
And, of course, you can always cold wash before scouring if the fleece is especially dirty.
*Heavy lanolin fleeces can be cold washed to help remove excess dirt, but most also require scouring. Too much lanolin can make it difficult or impossible to process for spinning.