That is the question everyone should be asking, especially if selling or buying a full fleece on the internet or when not able to touch the full fleece in person. Let me explain....
"Skirting" is the action of dividing up or separating the bad stuff from the good stuff of the fleece. In alpacas, the "bad" stuff is usually around the edges of the blanket and will be courser, shorter and probably more hairy. This will degrade the "good" stuff that took a whole year to grow. And for many of us alpaca owners, this is our cash crop, the fiber art stash that will help support the animals with their yearly cost.
Now, the "bad" stuff can also be pine cones, branches, twigs, shafts of hay/straw, etc. This is often called VM or vegetative matter/material. When I take a bunch of fiber and squeeze, if I feel any of the above mentioned, I pick it out. Obviously, if I see it, I pick it. Now you can make this process easier by grooming your pastures, dry lot area, etc before shearing. I don't know of any alpaca person that coats their animals like some sheep people do. So, that isn't really an option. Plus I can't image the coat staying on correctly and safely with the way these animals love to roll around and move.
I live in the high mountain plains of Montana, and have had to mow and chainsaw out the sagebrush in our pastures just for this purpose. Alpacas love to rub and roll on things. If it isn't the fence, then it's the sagebrush. I learned quickly that it was a pain in the you know what, to pick that out. So every year, I inspect my pastures and clean up before they can rotate into that section.
My normal pre-shearing routine (the week of) is that we clean our corral of winter's hay rejects and manure. We then will dry lot them with limited hay and the morning of shearing, I will quickly go over them with a large tooth comb and this "flicks" off the most superficial VM. I can also get my hands on them and feel (by squeezing the fiber) for larger objects. I do not blow or vacuum my animals. Why? ....probably because I don't have the means to, nor the desire.
During shearing, I try to be diligent with picking up the blanket and separating it before my shearer gets too much into the belly seconds area. I'll admit, it doesn't always work out that way, but I try. Things get put into their respective bags and boom! Three months go by and now I'm ready to skirt.
I'm not sure how people REALLY know what they have as a fiber fleece if they skip this part. Besides getting the sample ready to send off to the lab, this is when I get to measure the length, look better at the crimp, inspect fiber diameter, check out the density and see how the animal is aging. If you don't do this, how do you know what you have to sell? And if you don't know what you have, then you definitely don't know what price to ask for. There is more to a fleece then "it's alpaca and it's brown". OH, by the way, it should be sold by the pound, not the ounce at this point.
Step one: I dump out the bag of fiber onto my repurposed sun porch window screen that sits easily on two sawhorses. At this moment it is called an unskirted fleece. Now I can easily see the odd pieces that are courser fiber. Sometimes it is a little bit different color or it just doesn't look like the softer fiber. I will go around the edges, as it is still in the shape of the bag and pick out the "bad" stuff. Trust your hands, they know the difference between the good stuff and the bad.
Next I gently start of separate it back into the shape that it was sheared as. Weathered side and cut side will separate if you are gentle. It is helpful if your skirting table (really it should be called skirting screen) is big enough to allow this to occur. Wither you end up with the weathered side up or down, it doesn't matter. I inspect both sides and so should you. When it is weathered side up, I can see pieces of VM that I have missed. When it is down, I can see second cuts or odd colored fibers/hairs. Step two, completed.
SNOB ALERT: Please do not base your description of the softness of the fleece on what you feel when you touch the cut side. It always feels soft. This is, to me at least, false advertisement.
I will walk around my "table" and see how the bad stuff kind of wants to fall away from the main fleece. I sometimes equate this to pulled pork in the crock pot. When it's done, the meat wants to pull away. The good stuff of you fleece, will stay together, the bad stuff, will already be starting to pull away. So pull it away and save it or trash it.
Also look for length differences. You can grab the good stuff from the middle of the spread out fleece and find its consistent length. As you move down the fleece towards where the bad stuff was, if the length is getting shorter, you may not want it. These are things to consider what you want the final fleece to look like. The diameter of the fibers will also start to change and are easy to spot when you have trained your eye. Again, pull it away and save it or trash it.
Step three is bounce your left over good fiber on the screen and watch all the fine dust land on your garage floor. I highly recommend taking an allergy pill if seasonal allergies affect you. This only gets a small percentage of the dust out, but its a start. Re bag and go weigh it as this is now a skirted fleece.
Now back to the original question: To skirt or not to skirt? If you are reading this because you are interested in selling a fleece or looking to buy a fleece, I said earlier that it should be sold by the pound and NOT the ounce in this state. Why? Well for a couple of reasons.
1) unskirted fleeces are really not the true weight. If ALL that bad stuff (VM, courser fiber, dust) is still apart of the fleece's weight, you are paying for stuff that you are going to be throwing away. Not to mention the extra weight in shipping cost. If you bought 4 ounces of an unskirted fiber, how would you feel if you only ended up with 1 ounce or less of actual usable stuff? Same goes true with by the pound, but at least you will have more good stuff to play with.
2) skirted fleeces are getting closer to the true weight, but still off a bit. I can weigh my unskirted fleece at 6 pounds, skirt it to 3.5 pounds (I also tumbled mine vs just bouncing it) and after washing, may have 2.75 pounds.
Don't get me wrong, raw fleeces are awesome. Internet sells are becoming the wave of the future, but you need to know what you are getting into when it comes to unskirted vs skirted fleeces. Do you want to skirt it yourself? Is your definition of lightly skirted the same as the next persons? Look closely at the pictures if a potential internet purchase, you can often see how skirted or unskirted it is. If selling, please show how it looks too.
This leads me down the rabbit hole into another topic. But I am going to post that a later time. Just a little teaser for now.....what important points should photos show for internet selling/buying?