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Skandinavisk Impregneringsservice

Essay 5


Wood has been used as an article of construction since before the dawn of civilization.
One of the earliest methods of increasing the durability or longevity of wood was fire, hardening the tip of a wooden spear or arrow. This caused the resins in the wood to harden more than what was produced by the living tree, giving a stronger, more durable point that more efficiently pierced simple leather armor, and gave an efficient kill to game animals. This process also sterilized the wood, which was important since the varieties of fungi which eat wood are many and common on this planet.
Some varieties of wood also contain natural antibiotics and these when present help to give the wood longer life by giving resistance to the micro-organisms that regard wood as food.
Wood used for weapons or other utilitarian articles tended to wear out before it rotted, while wood used for construction tended to rot before it wore out. In relative terms, wood wore out quickly but rotted slowly.
Wood used for architectural purposes only, exhibited long life under extremely cold conditions or when in an oxygen-free environment, as the micro-organisms which feed on wood requires oxygen. The air is about twenty percent oxygen.
Old wooden ships hundreds of years old and buried in mud have been found and wooden ships and buildings hundreds of years old and in very good condition have been found in Arctic climates such as Alaska and northern Canada. It is possible that the fabled ark of Noah, several thousand years old, has been found entombed in ice on Mount Ararat in Turkey.
When wood was used at temperatures where fungi and bacteria are active, the only known technology of "restoration" was to cut out the deteriorated area and glue in a fitted replacement portion. In ship repair, in the last hundred years, the insert was known as a "dutchman". For general repair and preservation hot tar might be used. While creating a somewhat waterproof seal with little physical strength, hot tar tended to sterilize the wood and this plus the tendency to seal the wood from the air at the location where the hot tar might be applied, contributed to the longevity of this technology. The Indians of the North American continent used tar as a sealant for birch bark canoes.
Tar or Pine pitch or a mixture was commonly used as a sealing compound between the deck planks of wooden ships hundreds of years ago. The material was heated and poured into the seams where it solidified. The decks were thus sealed against water and rain leaking through to the cabins below. The sailors were usually barefoot and on hot days the tar would melt and transfer to the soles of the feet. British sailors thus acquired the nickname "tarheels".
The surface protection of wood was accomplished by treatment with the oils of various beans, berries or seeds which had been found to dry and harden on exposure to the air. This material, today, we call varnish.
Joints between separate pieces of wood on older boats were usually filled with a paste of fibrous material, lead oxide, and various vegetable oils or varnishes. The lead oxide served as a primitive fungicide to deter the rot which would begin when the inevitable fungus spores, carried by air or water, got into the space between two pieces of wood and proceeded to hatch, grow, and eat the wood.
An early method of increasing the rot resistance of wooden ships was to paint the masts, spars and other parts black. This absorbed more heat form the sun, dried out the wood after it had been rained upon, and thus fungal decay was reduced by keeping the wood more dry more of the time.
The marine environment is hundreds of times more severe than the architectural environment, in terms of both dampness and mechanical stress. Technology was thus forced to develop for marine maintenance and restoration, where little technology was forced to develop for architectural maintenance and restoration.

The Dawn of Contemporary Wood Restoration Technology

In the 1950's Shell Chemical Company invented a commercial process for manufacturing a type of resin and a variety of curing agents for it. The family of adhesives and coatings which were developed from these products turned out to be surprisingly versatile and compatible with a wide range of wood and metal and concrete materials. The U.S. Department of Defense rapidly developed improved versions of these paints and adhesives in their own research laboratories, to meet a wide range of military applications. They then solicited bids from the existing paint industry to manufacture these formulations. The industrial community was thus given a "jump-start" in commercializing products based on these resins.
Many large and small companies began to make "commercialized" or lower-cost versions of military formulations and to offer them to industry and the general public for just about any possible application, with no serious applications technology. By the late 1960's ~ 1970's many small businesses had developed architectural maintenance products which were moderately successful, although a common failure mechanism was that some one to a few years later a filler in the wood might be seen to come loose and rise up under a coat of paint, or rot to start up again behind a spot that had been "treated" with some "restoration" product. These architectural maintenance products could not cross over successfully into the marine market place, as the quality of restoration possible in the architectural market was such that with luck a repair might last five or ten years; in a marine environment that same quality of repair might last three months to two years. The technology was not viable in the more severe marine environment and only barely viable in the architectural environment.
Thus, there were no epoxy restoration products successful and expanding in either the marine or architectural market places.
In 1972 Steve Smith became aware of the need for something to handle deteriorated wood on boats from a friend in the marine business. He whipped up something and told his friend to "try this". The short term results were so successful that a demand appeared almost overnight, and the first formulation of the Lignu® Impregnating Resin (as it would come to be known thirty years later), embodying the fundamental principles of the technology (though far from optimum) was introduced to the marine marketplace. By 1976 the product had spread to the architectural restoration marketplace, a filler and a glue had been added to the product line, and sales volume had dramatically increased, with the business growing from one person to six employees.
Meanwhile, the technology was evolving and becoming optimized and more refined as the actual needs of the end users become better understood. Various painting contractors and remodeling contractors had begun to use the product for routine maintenance and restoration. The State of California State Architect's office and the State of California Department of Parks and Recreation found out about the products, evaluated them and began to use them for the restoration of various historic structures.
A boat builder who happened to be working for the U.S. Government, stationed on Kwajalein Atoll in the South Pacific (part of the Pacific Missile Test Range), found that the Lignu Impregnating Resin was useful in the maintenance of the wood buildings on Kwajalein which housed the radar and electronics gear. Thereafter anywhere from thirty to two hundred gallons every few months were sold to the U.S. Government and shipped to Kwajalein for continuing restoration of the wood buildings. This is significant because Kwajalein is hot, humid, and gets about a hundred inches a year of rainfall. The product was successful in maintaining old and new wood buildings that, before this time, were simply torn down and replaced every few years. This continued thought the end of the Cold War and the closure of the Pacific Missile Test Range in the early '90's. The radar station is now used as a mid-Pacific air traffic flight control center, and the use of this product continues.
Thus, once a viable technology for the restoration of deteriorated wood in a marine environment was developed, it spread and expanded rapidly in the architectural maintenance market place since it was an inherently viable technology.

The Modern Technology that restores deteriorated wood.

The technology underwent significant refinements in the laboratory in the late 80's and early 90's but none of this was released to the public since it was felt that a better customer training program would be needed to take best advantage of the latest refinements. The present customers had learned about the products through word-of-mouth or some limited advertising, and the only training possible for mail-order customers was the enclosed literature package. After observing the effectiveness of such training, Steve Smith decided that the newer, high-performance versions would only be used by those formally trained in a classroom environment due to the much better and more consistent results available from such training.
These "consumer-grade" products had, over the years, gained great acceptance among end users, including some pest control operators ("Exterminators") who used the product to restore deteriorated wood despite written rules from their regulatory agency stating deteriorated wood must be removed. The technology did not have a theoretically derived origin but rather an experimental one. Thus, no authorities in the Forest Sciences Departments of Universities had evaluated the product and measured the properties of restored wood and certified that some percentage of restoration could be reproducibly achieved and measured under standard test conditions. This is in fact impossible, since there is no such thing as a standard piece of rotten wood. Thus, no restoration standard was possible.
City building inspectors were now commonly coming into contact with the products and their use in a variety of circumstances and more questions arose, as restoration of deteriorated wood is not covered by any building code. Yet, people were using it and it seemed to work, the test being to jab the wood with an ice pick to assess the state of deterioration by the degree of penetration. After treatment with the Lignu Impregnating Resin, the treated wood resisted penetration by an ice pick in a similar manner that new wood did. Thus, restoration was accomplished in fact if not in law.
In 1997 a surrogate standard for deteriorated wood was invented by the discovery that the common cedar shingle had a very similar absorption of Lignu Impregnating Resin as lightly rotted wood. A series of tests were then done, using the professional Version ™, comparing treated wood and untreated wood, and actually measuring the effects of restoration of wood with this technology. The results are published at
The building code and pest-control-operator ("Exterminator") regulations do now address restoration. References are cited at the end of the above publication.

The Future of the Restoration of Deteriorated Wood.

The development of the professional versions of these products has now been accomplished, based on the knowledge gained and refinements and field tests and evaluation of the last 24 years. The trademark Lignu was created and registered to denote the modern, high-performance family of wood restoration products. A training program for the use of these products has been developed and technicians have been trained and are capable of applying the products and the underlying technology.
In the Spring of 2001 the Lignu Specification was published on the U. S. site of, and the State of California department of the State Architect issued guidelines for restoration of deteriorated wood on all State property overseen by them, including schools. This applies to structural as well as non-structural wood elements.
Wood is commonly used in construction, has been for hundreds of years and will certainly continue to be for hundreds of years due to the low cost and high production rate of wood by the natural vegetable life forms of this planet.
Since the technology relies on restoration of deteriorated wood using, in great part, materials actually derived from wood, these products and this technology will persist as long as wood itself is used in architectural construction.

Copyright © 2002 Steve Smith All rights reserved

Essay 1
An introduction to paint, varnish and the Lignu Resin on wood
Essay 2
Clear coatings on wood
Essay 3
Essay 4
How to get more life from paint on old, weathered wood
Essay 5
Essay 6
Essay 7
Essay 8
What's the Matter?

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