Technical Information

About Wool


Section 1 - General


"Each wool fibre is a molecular coil-spring making the fibre remarkably elastic with high resilience characteristics. Nature has folded the chemical polypeptide chains back upon themselves in such a way that they act like a coiled spring which elongates when it is extended and retracts when it is released.

This molecular crimp, along with the 3-dimensional fibre, allows wool fibres to be stretched up to 50% when wet and 30% when dry, and still bounce back to their original shape when stress is released."


Section 2 - With background and references


"There is a common misconception that wool is best suited exclusively for warmth in cool conditions. Scientific tests however negate this concept and consistently show that wool is ideal for apparel and bedding in hot, humid, dry, cold or wet conditions.

Wool has unique attributes, which give it superior performance to other fibres in a number of ways. Our bodies continually produce heat at a rate dependant on our activity level; this heat must be dissipated to the surroundings in the form of perspiration, at the same rate at which it is produced, to keep the body temperature constant(1.). When used in bedding, wool creates a microclimate, which assists in regulating body temperature and humidity. The degree to which body temperature and humidity is regulated is known as thermophysical comfort, that is, a state in which the individual is free from thermal stress.

Freedom from thermal stress is directly related to degree of rest. There are a number of thermophysical responses which can be measured to indicate how well rested a person is at any given time. Several studies examining and comparing the performance of wool underblankets have consistently shown that in hot and cold conditions wool provides comfort and a more restful sleep than any other fibre type.

Dr K H Umbach from the Hohenstein Institute in Germany designed and undertook a series of studies to determine the measured responses, which are most indicative of a rested nights sleep(2.). He found that first and foremost that the heart rate is the most accurate indicator. A person with a slow and regular heart beat is far more relaxed than a person with a fast paced and/or irregular heart beat. Two factors, which will be reflected in the heart rate, are the temperature and humidity of the bed microclimate. It is a well known fact that in order for the major organs of the human body to function efficiently, the core temperature must be maintained at or near 37ºC.

Using the thermophysical responses related to sleep behaviour, Umbach monitored several body and climatic functions to compare the performance of wool versus acrylic underlays(3.). Subjects were monitored in environment controlled (temperature, humidity and airflow) rooms. It was found that the pulse rate of sleepers under the wool blanket was normal at 60 beats per minute, whereas it rose erratically up to 80 beats per minute under the acrylic blanket, indicating greater stress on the sleeping person. This was easily explained by Umbach's other observations: the wool blanket absorbed 50% more perspiration than the acrylic blanket, and cotton pyjamas worn by the participant remained drier while they were under wool blankets. The microclimate under the acrylic blanket was too hot and humid for comfort.

The Ergonomics Unit at the Polytechnic of Wales compared comfort properties and sleep patterns of subjects sleeping under duvets rather than blankets(4.), again in an environment controlled room. When the bedroom was at 16ºC all sleepers were comfortable although the humidity under the wool duvet was lower. Interestingly, pulse rates under the wool filled duvets were again found to be lower than under the polyester filled duvets.

However, at 22ºC the results were statistically discounted because the subjects under the polyester bedding exposed their limbs for periods of time in an effort to cool down. This response was a poor substitute for the thermophysically controlled microclimate as found under the wool duvet.

A third trial designed by the Dickson used the subject's own room and bed as a control. Time lapse photography monitored movement during the night to determine the sleep quality(5.). Dickson found statistically significant differences in the number of immobile periods, immobile sequences, and the percentage of total time spent sleeping on the wool underlay compared with the control surface. Again the wool underlay was proven to be the most restful surface to sleep upon.

The positive health effect of sleeping on wool is best illustrated by a study by Scott(6.) of low birth weight babies. This study found that babies nursed on lambs wool consistently showed a significant improvement in weight gain over and above those nursed by conventional methods using cotton.

Wool's comfort advantages have traditionally been attributed to the capacity of the fibre to absorb a significant proportion of its own mass as water(7.).

Researchers agree that more than simply absorb, wool fibres have the ability to buffer by reacting to the humidity level within the particular environment. As the humidity rises, wool will absorb and store moisture as required. When the level decreases, the fibre releases the moisture thus regulating the microclimate. This property ensures that a damp, clammy feeling will never be experienced with wool. In this way, instead of the body regulating the microclimate, the wool bedding acclimatises the body, ensuring a healthier rest with an even heart rate and blood pressure.

Another advantage of wool over other fibres is its outstanding insulating properties especially when compared with synthetic fibres(8.). The unique three-dimensional form of wool allows it to trap small pockets of air, thus giving it an insulating property. This property ensures that temperature changes are slow and gradual so that the beds microclimate has time to equilibrate. Rapid changes in heat loss or gain would hinder temperature and humidity regulation.

Wool's natural resilience is another property that aids comfort. The pile of an underlay will reduce pressure points and cushion the body. Tests using underlays with elderly and bedridden patients in hospitals have shown dramatic differences between the performance of wool and polyester bedpads. The following results clearly identify the advantages of wool.

Patients on wool had significantly fewer skin problems than those on polyester pads. 77% of those on wool had no problems compared to 38% on polyester. Of those with debcubitus ulcers*, only 8% had a problem for more than one month while 38% on polyester had problems for a period for more than one month.

In addition, no patients on wool pads had renewal of skin irritation once the initial problem had cleared up while 14% had repetitive periods of irritation on polyester(9.). The health aspects of sleeping on wool continually out ranks similar synthetic products."

*Bedsore: A pressure-induced ulceration of the skin occurring in persons confined to bed for long periods of time. Also called decubitus ulcer.


Section 3 - Specific to Nursing Pads using some references from Section 2


"Wool pile nursing pads are often used in hospitals and homes for the ill and elderly to prevent bed sores and discomfort for those who are immobile for long periods of time. Like sheepskins which are also used for nursing, wool pile fabrics have many characteristics that alleviate pressure, moisture and friction - contributors to the development of bed sores. Because of wool's resilience, the weight of a patient is distributedover a larger area, eliminating local pressure points where bed sores form. The softness of wool minimises abrasion to the skin and wool's moisture absorption keeps skin dry and comfortable, preventing 'clamminess'.

Special paediatric nursing pads are available for babies. Research at Cambridge University has shown that premature babies in incubators grow faster lying directly on pure new wool pile nursing pads than on cotton sheets irrespective of the baby being well or ill. While there are no studies available comparing nursing pads made of wool and synthetics, researchers suggest synthetics are unlikely to be suitable for use due to their comparative inability to absorb moisture."


References


  1. Wool? Why is it Comfortable?, B Holcombe, Proceedings of the 8th Int. Wool text. Res. Conf., Vol V., fibre Assemblies and Product Properties, ed G H Cranshaw (WRONZ) 1900, 205-214.
  2. Comparative Thermoplysical Tests on Blankets Made From Wool and Acrylic-Fibre-Cotton Blends, K H Umbach, J Text. Inst., 1986, No 3.
  3. Comparative Thermophysical Tests on Blankets Mde From Wool and Acrylic-Fibre-Cotton Blends, K H Umbach, J Text. Inst., 1986, No 3.
  4. An Ergonomic Comparison of Wool and Polyester-Filled Quilts, Polytechnic of Wales, Ergonomics Unit, published in IWS Technical Letter Number 26.
  5. Effects of a Fleecy Woollen Underlay on Sleep, P R Dickson, The Medical Journal of Australia, January 21, 1984, p87-89.
  6. Weight Gain and Movement Patterns of Very Low Birthweight Babies Nursed on Lambswool, S Scott, P Lucas, T Cole and M Richards, Child Care and Development Group University of Cambridge and the MRC Dunn Nutrition Unit Cambridge, Oct. 1980-Sept. 1981.
  7. W E Morton and J W S Hearle, Physical Proporties of Fibre, The Textile Institute Manchester, 1986 Edition.
  8. Wool Pile Sliver Knit Bedpad Evaluation at Franklin Park Nursing Home, L R Mizell, W H Marsden and V Butler, Summary report by New Market Outlet Section, IWS November 1974.