“Well, lots of factors are going to effect our analysis, if we’re comparing the density of different alpacas. The length, but especially the micron right? So the first thing to do, is to assess the micron - and then guesstimate how much that should effect the difference between, say, alpaca number one and alpaca number two. Let’s say we decide #1 is 15 microns, and #2 is 30 microns. Assuming they are equally dense and long, #2 should feel like he had twice as much fleece on him, right?”
That seemed pretty significant to me.
“Nope”, Math Guy says (AKA Rus) - “That’s 1 dimensional thinking. You’re trying to assess 3 dimensions: volume. Alpaca #2 would have 4 times as much fleece on him”.
“No way! How do you figure?”
“Simple - It’s Pi - r - Squared. It’s how you figure the area of a circle - or in the case of 3 dimensions, the volume of a cylinder. Just ask any guy that has had to ship pipe. Double the diameter and it takes up 4 times the space.”
Show me - I say - and we’re off and running.
First of all - we should back up and ascertain just what the heck are we trying to assess anyway. Density - we are taught to assess it with “volume checks” - the “grab” at the side, the push down on the top, the resistance we feel when parting the fleece.
Isn’t that what we’re looking for? Thick voluminous fleece?
Not exactly - that would be perceived density, or more accurately, volume. What we are trying to determine is a comparative True Density - the relative number of follicles per area of skin.
If we are breeding for both increased fineness, and a higher number of follicles per area of skin, we will be rewarded with a better market for our fleece. Finer fleece and more of it! That’s the goal for many of us, as fiber buyers will pay significantly more for finer fleece than for strong. Our fiber production farms will have a higher profit margin, if each alpaca is carrying more, fine, fleece. In order to make the best breeding choices to reach these goals, we must be able to correctly assess the effects of fineness on our perception of density, or volume.
There are many methods folks use to try to determine the true follicular density of an alpaca. An actual skin biopsy is bound to be the best method, right? For now, the jury is still out on biopsies. The variations in results between different laboratories, and the relatively few alpacas tested so far, don’t allow us to bet the farm on those results alone just yet. We do expect that it will be valuable in confirming some of our assumptions. But for now, we are focusing on assessing true density without the benefit of this type of procedure.
So we come back to my original rant . . . .
How can we come close to correctly assessing the Impact of diameter, AFD, on volume -
while the fleece is still on the alpaca?
This resulted in the creation of the next chart - which compares the relative space taken up by various fiber microns, from 10 to 30 - so I could have a reference to work with. The “volume value” is a relative number - simply used to compare the space taken up by fibers of different diameters. (see diagram)
Then we applied these relative volume values to fleece weight -
which resulted in the following chart:
Annualized fleece weights provide very valuable information when assessing follicular density, when combined with an accurate AFD, and staple length. We have focused a great deal on fleece weight to help validate or refute our attempts to mathematically assess density on the alpaca. For example, lets say we have an individual that increases by 2 microns a year for 3 years, from yearling through 3 years of age; and we have accurate total fleece shearing weights plus staple lengths. We can plug that data into our chart and see if it agrees. The assumption is that this individual alpaca has not changed it's follicular density. So we should be able to calculate his increase in fleece weight given the change in AFD information. Sure enough - it has worked very accurately in most of our test cases.
These charts were created to give us a visual impression of the differences we can expect to feel, in the volume of fleece carried by alpacas of different microns. You can use them in your herd, by just taking two alpacas of known AFD, with similar length of fleece. Do the standard "volume" checks, the resistance test, the fill up the hand tests, etc. Check the chart, and find, that for instance, if one alpaca is 17 micron, and the other is 23 microns, the 23 micron alpaca should feel like it has almost twice as much fleece as the 17 micron alpaca, if they had equal follicular density.
I've used them on my herd and found that my previous assumptions, as to which alpacas were the most densely packed with follicles, were not as accurate as I might have hoped. I also found it explained why several females in my herd had failed to breed up as well as expected. I had classified one as extremely dense, but needing fineness. Bred to a pretty dense, very fine male - I would get crias that were less dense than the male, and less fine too. Because, with the benefit of comparative fleece weights and microns, and using our chart for guesstimating how much more fleece she should feel like she had on her, at her micron . . . . she wasn't an extremely dense female after all. Yes, you could balance a brick on her. But no, she was not densely packed with follicles. In hindsight, the sire we were breeding her to was actually denser in follicles than she was. So the follicular density of the crias was between that of the dam and sire, as was the fineness, resulting in an average cria in both categories.
Some unknowns that we may not have considered in some of these assumptions, include the effects of "between" space - between the fibers on the skin level - on our perceptions; and the possibility of the weights of the actual fibers from various alpacas differing.
Other factors that effect our volume and density assessment, which we have given a good deal of thought to, include the presence or absence of locks, and general fleece style. Stay tuned for that discussion in Part 2!
Part 2 -
Fluff versus Locks.
On a related but different tack -
I also had a very interesting discovery recently, when preparing 5 fleeces for a spin off. When entering a spin off, we are instructed to prepared 2 ounces of clean fleece for each alpaca.
If you’ve never entered one of these, let me tell you, think tedious. Especially if you are as obsessive as I evidently am! Tell me to “clean a fleece” without disturbing the architecture . . . . Yeah right. Might as well tell me to mow the lawn without damaging any blades of grass.
I had noticed, as I went, that some of the fleeces filled up the gallon sized bag more than others - but I didn’t think much on it - till I got to the last one. I grab a wad of his crimpy locks (the kind that look like little caterpillars) - pull out a few pieces of hay, and toss it in the bag. Thinking, well I’m about half way there, I toss the bag on the scale to see how much more I have to go.
Done. It’s already 2 ounces.
Wait - why did "Fluffy's" fill the bag so much when I hit 2 ounces, that I had to push it down just to closed the zip lock, While "Locky's" just sits there in the bottom 1/2 of the bag? The difference? Lock structure. Locky's locks are heavy and dense.
Fluffy’s fleece seemed extremely dense while it was on her. She showed very well and received good comments on her combination of density and fineness. Based upon grabbing (filling the hand) and resistance when parting the fleece, she has volume.
She is fine - at 18 microns - has exceptional crimp, beautiful when opened up - but she has little in the way of Locks, per se. Locky's heavy, finer (16 microns), dense crimpy locks hang down and made him seem Much less dense than Fluffy, when you feel him for resistance or grab the fleece on his side. But after shearing, with benefit of fleece statistics like weight, length and micron, Fluffy has a much lower true density than Locky.
I am just discovering, that when assessing density - fluff - or a looser lock structure, versus dense locks, has been very misleading to me.
With suris, from what I have gleaned, fleece density is judged (on the alpaca) by possibly “weighing” the locks in the hand, but then primarily, by assessing the density of each lock by squeezing between the fingers. There is no real “volume” testing when assessing density on a suri. In fact, volume (fluff) is associated with negative traits in suri fleece.
It occurs to us that some styles of huacaya fleeces have a tendency to hang down more than others. Those are the ones with very dense heavy locks, and long staple length. Density and length are factors that increase lock weight, pulling down the fleece. Both of those are desirable traits from a fiber processing standpoint. But both give the impression of less volume.
Grabbing the side of this very desirable type of fleece to assess density can be deceptively unrewarding.
The undesirable factor that increases weight is micron. To attempt to remove this factor from the equation - pull some strands of fiber and assess the diameter -First.
A term used to measure yarn weight in the textile industry is Tex. By definition Tex is: the weight, in grams, of 1000 meters of yarn. Yarn made with fibers that possess a high frequency crimp, tend to create a yarn with more volume in it, and less weight. Light weight is desirable in many garments, so for that reason, crimp is considered desirable. Yarn made from fibers with no crimp requires more fibers to take up the same space or volume. So a yarn that is the same thickness would be heavier. Keep in mind - these are carded fibers - crimp is now independent for each fiber. Locks have been completely disrupted. So the crimp now creates volume by pushing away the neighboring fibers.
Stay with me here . . . . The point I am heading towards, is back towards the evaluation of the impact of lock structure on volume. A dense lock with uniform well aligned crimp acts like the fibers previously mentioned in high Tex yarn, that are straight. They are still in perfect alignment. The less dense the lock - the less perfect the alignment - the more volume. On the alpaca, we could say, we should be selecting for High Tex locks - because that is our best indication of a high density fleece, and high fleece weight. We are also selecting for low diameter fiber, with high amplitude crimp - that will, once carded, produce Low Tex Yarns.
This discussion on lock structure does not include any answers, on a method of analyzing it's effect on our assessing density. It's just to point out that it is another factor that greatly impacts our assessment of density on the animal.
Which brings us full circle. There is no mathematical calculation that can remove the expert hand from the ideal total assessment of an alpaca fleece. But we can add a more correct perspective to refer to, by using accurate mathematical thinking. Start with assessing the AFD, then add in all of the other factors you have before you; heaviness, length, lock structure versus fluff factor, and the volume (grab and resistance).
Factor the AFD to Volume ratio into the assessment. (see the chart).
But of course, in the end, we all go with our heart, or as some say - our gut instinct. With lots and lots of experience, that gut instinct becomes the factor that you will depend upon the most.
As much as we overanalyze the tests and calculations, many of the fleece traits we prize the most cannot be measured. Handle. Fiber Scale structure. Prominence or style of guard hair. Those traits are selected for by learning Not to second guess yourself too much. If your first impression is “ohhhhhhh” and a big smile . . . . don’t rationalize that away!
But if you’ve discovered some “aha” tidbits in here by sharing my recent refreshers in geometry, perhaps adding a few new landmarks to your density map might be a good thing.
(article copyright Delphi Alpacas 12/08/2009 - graph; 2/4/2010 - article)
