Layering is simply a strategy that emphasis versality and efficiency. Instead of bulking oneself with heavier items it is always better to put together an outfit with lighter items that can be removed or worn depending on the situation.
Layering is a tried and tested way to maximize the comfort. The success of this concept is that it allows one to make adjustments based on the activity level and changes in weather. Venturing into the Himalaya, one cannot predict the way the weather changes above 3000 mts. Hence one has to be prepared. I would be speaking on some of the terms that we use when we talk about preparation for outdoors in terms of clothing as well as how to choose what would be the correct and most flexible option.
First let’s begin with the terminology:
Base Layer: This is the next-to-skin layer.
Mid Layer: As the name indicates this is the middle layer catering to insulation.
Shell Layer: This is the outermost layer designed to deal with the elements of nature.
Powertec powder Dry: This patented technology used in base layers gives greater efficiency to the fabric improving drying performance and better performance using the characteristics of wicking in an improved design.
Synthetic Fabrics: These fabrics use powertec powder dry and related technologies in order to make state of the art base layer.
Merino Wool base layer: Over the years few brands have revolutionized the use of Merino wool for base layers.
Numbers alongside a particular model: The numbering alongside terms like midweight, lightweight, heavy weight indicate the warmth index. The higher the number, the higher the degree of warmth.
Fleece jacket: A lightweight jacket which uses polyester synthetic wool like polar fleece.
Down feather: The down refers to a layer of fine feather found under the tougher exterior feather in specific birds like goose, which are used as a fine insulator in jackets and sleeping bags.
GORE-TEX: Gore-Tex is a waterproof, breathable fabric membrane able to repel liquid while allowing water vapour to pass through.
VIBRAM: VIBRAM is a special material used in soles of mountaineering boots which has revolutionized the way Hiking/mountaineering boots.It provides excellent traction, abrasion resistance.
for detailed information on layering and several related articles , click on this link
Why Layering: a perfect natural query and I would like to summarize
(a) To keep oneself dry from the moisture that the body produces
(b) To keep the body heat trapped
(c) To keep the weather elements from affecting the body.
For a deeper understanding, let us begin:
Base Layer: This is the next-to skin layer. It helps in regulating the body temperature by moving the perspiration away from the skin and thereby keeping the body at a cool working temperature both in summer as well as winter. This layer is not meant to keep one warm, this needs to be remembered. Generally made of synthetic polyester, merino wool or sometime silk it offers breathability to the skin which is of paramount importance. Generally, preference is to be given to zip necked long sleeves models. Also to be kept in mind is that on long treks of over 05 days trekkers generally prefer only two pairs of base layers in order to minimize weight, hence the base layer should not smell as days pass by, is an important consideration while selecting. Never opt for cotton as it holds perspiration and that can play havoc with the working temperature of the body.