Wood wool, known primarily as excelsior in North America, is a product made of wood slivers cut from logs. It is mainly used in packaging, for cooling pads in home evaporative cooling systems known as swamp coolers, for erosion control mats, and as a raw material for the production of other products such as bonded wood wool boards. In the past it was used as stuffing, or padding, in upholstery, or to fill stuffed toys. It is also sometimes used by taxidermists to construct the armatures of taxidermy mounts.
Terminology
In the United States the term wood wool is reserved for finer grades of excelsior. The US Forest Service stated in 1948 and 1961 that, "In this country the product has no other general name, but in most other countries all grades of excelsior are known as wood wool. In the United States the name wood wool is reserved for only a small proportion of the output consisting of certain special grades of extra thin and narrow stock."
The US Standard Industrial Classification Index SIC is 2429 for the product "Wood wool (excelsior)". The same term is used by the United States for the external trade number under which wood wool is monitored: HTS Number: 4405.00.00 Description: Wood wool (excelsior); wood flour.
The number 4405.00 is applied to wood wool by the World Customs Organization in the Harmonized Commodity Description and Coding System (HS).
Grades and classifications
The 1973 US Federal Government procurement specification PPP-E-911, cancelled in 1991, categorized "wood excelsior" products according to the following table of terms and dimensions:
Applications
Excelsior has many applications; examples include:
restoration of antique buggy seats, and furniture. a packaging material for cushioning, such as Fibrenap (Cushy Pads) a stuffing for plush toys or for real animals in taxidermy. It was traditionally used in stuffing Teddy bears and still is for the muzzles of some collectible bears. cooling pads in home evaporative cooler systems known as "swamp coolers." bedding for animals and their cages. Wood wool serves to cushion the animals while providing some warmth and absorbing waste. For example, it is found in dairies, in hutches and in cardboard boxes when shipping day-old poultry within the United States. when dyed green, the material can be used as an artificial grass in Easter egg baskets. This was popular before the prevalence of plastics. mats and blankets for erosion control. a material used in the production of cement-bonded wood wool boards. when banded into a bale form, it is used as an archery backstop, comparable to how a straw bale would be used for the same purpose. If protected from the elements, an excelsior archery backstop can last for many years. If sections of it wear down because of repeated targeting, the bale can be soaked liberally since it then expands and holds water, just like a dry sponge. garden mulches and as a growing medium for hydroponic gardens.
Properties
Wood wool fibers can be compressed and when the pressure is removed they resume their initial volume. This is a useful property for minimizing their volume when shipping. Due to its high volume and large surface area, wood wool can be used for applications where water or moisture retention is necessary. The width of wood wool fibers varies from 1.5 to 20 mm, while their length is usually around 500 mm (depending on the production process).
In the UK there are specifications for dimensions, pH, moisture content and freedom from dust and small pieces, set by British Standard BS 2548 for wood wool for general packaging purposes. This standard was originally issued in 1954 and subsequently re-issued in 1986.
When these fibers are bonded with cement or magnesite, bonded wood wool boards are produced. Slabs of bonded wood wool are considered environmentally friendly construction and insulation materials because they do not contain organic binders.
Production
Excelsior is cut from "bolts" (round, halved, quartered, or otherwise split logs) of poplar (for example aspen), pine, spruce or eucalyptus. For evaporative cooler pads, the dominant source is the aspen.
Wood wool can be produced in either horizontal or vertical shredding machines.
A possible further processing option is washing, which removes dust. Wood-wool processing may involve drying to reduce moisture in compliance with local requirements, as in the UK.
Finally, wood wool can be dyed to produce a variety of colored products.