Alpaca fiber testing for properties that we often promote when discussing fiber products such as “warmer than,” “insulating” and “antimicrobial” have been on AOA's Fiber and Fiber Products Committee agenda for some time. The committee, under the direction of Ruth Fuqua, set out to determine the type of testing needed along with the best fiber testing laboratory to accomplish it. The committee wanted to determine the Thermal Capacity (total heat loss measurements) of alpaca fabrics and Antimicrobial properties of raw alpaca fiber. We are pleased to report these results are now complete with very positive results!
Antimicrobial Activity Testing
Testing was completed on both suri and huacaya fiber samples and performed in adherence with ASTM Standard E2149-13a. The samples were washed first to remove any soil that might interfere with the testing and then presented to the lab. The lab then autoclaved the samples to ensure they were free of any external source of bacteria. The samples were introduced with a known concentration of E. coli bacteria in a growth medium and the results were read after one hour of contact. This test is widely used in the textile industry to determine antimicrobial properties in fabrics.
We are pleased to report that after one hour of exposure to E. coli, the amount of bacteria present was significantly reduced. The viable bacterial cells in the huacaya sample were reduced by approximately 65% and in the suri, by approximately 79%. These results clearly show that alpaca fiber does indeed contain a degree of antimicrobial characteristics.
What does this mean for us as alpaca breeders and for fiber product sales? Consider the benefits to our end-products. Socks with this type of antimicrobial action are a benefit when wearing them for long periods of time. Hats, gloves, and mittens made from alpaca are also less likely to harbor and transfer bacteria. These test results now give us the ability to honestly say that alpaca fiber is antimicrobial in nature.
Thermal Conductivity Testing
When thinking about Thermal Conductivity, most people think of R-values, especially when it comes to construction insulation. For alpaca fiber, we were more concerned with the insulating properties of clothing which are reported in values most individuals may not be familiar with. A measurement called the Clo Value, which is widely used in the clothing industry and represents the heat comfort/insulation value of a given fabric, was determined. Values for permeability, which represents the heat retention value (breathability of the fabric) and Total Heat Loss, which represents the amount of metabolic heat generation that can be exerted without comfort loss, were also determined.
Testing was performed in adherence with ASTM Standard 1868 on both suri and huacaya fabric samples. Both knit fabric and felt were tested to expand the 2009 evaluation of woven fabrics. Each sample was 20”x20” in size and as close as possible to the same thickness in millimeters. This gives a good baseline for thermal conductivity properties in these types of fabric structures. It is important to keep in mind that the values can and will change, depending upon the thickness and construction (weave, knit, or felted) of the fabrics tested. For example, a knit base layer fabric will have different Clo Values, Permeability, and Total Heat Loss results than a knit cabled sweater. The results provided are a snapshot of the possibilities for alpaca fiber. While we can use our current results when promoting alpaca fiber, we must also be cognizant of the limitations of the results to our specific fabrics.
Clo Value Results
This represents the heat comfort/insulation value. A Clo Value of 1 is equal to the amount of clothing required by a resting human to maintain thermal comfort at a room temperature of 21 degrees Celsius, or 71 degrees Fahrenheit.
The values for the alpaca fabrics submitted all came in above 0.85, with the felt samples both over 1.3. To understand these values consider 1 R-value (think pink insulation values) = 1.137 Clo Value. A typical men’s suit is around one Clo Value, long underwear typically is about 0.15–0.20, and a long-sleeve thick sweater is about 0.36. As you can see, our values, using a very small fabric sampling, already have a higher comfort value than those typical items.
This relates to heat retention or air permeability.
Air permeability is dependent upon a given fabric weight and construction (thickness and porosity). You would expect a fabric with an open weave or knit structure to have high permeability, or more airflow through the fabric, and a tightly woven, felted, or double knit structure to have a lower permeability or less airflow through the fabric.
The values for the alpaca fabrics submitted all came in with permeability rates over 0.6 which indicates the fabrics will breathe and not create sweating. Remember, these values are specific to the weight and thickness of the alpaca fabric samples that were submitted.
Total Heat Loss Results
This represents the highest predicted level of metabolic activity level that can be exerted and still maintain body thermal comfort (for example seated quietly versus digging a ditch).
Once again the levels for Total Heat Loss (THL) in the alpaca fabrics tested exhibited a high degree of comfort level while exerting energy. Levels ranged from 272+ (huacaya felt) up to 428+ (suri knit). For comparison, the average THL for sitting quietly is approximately 60 while the THL for digging ditches is 345. The results indicate we could easily be digging ditches or shoveling alpaca poop comfortably without the need for cooling!
Following is a chart showing the results for all six fabric samples.
Thermal Conductivity — Testing 2009* and 2020**
Total Heat Loss
Clo Value: comfort for indoor wear based on heat comfort/insulation value
Permeability: the fabric will “breathe” and not create sweating — affects heat retention
Total Heat Loss: represents the highest predicted level of metabolic activity level that can be exerted and still maintain body thermal comfort (for example seated quietly versus digging a ditch)
These test results give alpaca owners specific scientifically supportable data for claims we make about alpaca fiber. Alpaca fiber is indeed antimicrobial (65 – 79% bacterial load reduction) and the insulating value, while maintaining comfort levels during activity, is also high (dependent upon the thickness of fabric and porosity) when compared to published metabolic rates for different activities.
The test results can be found at www.alpacainfo.com/academy/article/4754/alpaca-fiber-studies.
Presented by Ruth Fuqua and Wini Labrecque