In part three, we took an in-depth look at the fourth class of wood preservative treatments: water soluble boron compounds. We saw how, despite some manufacturers' claims, sodium silicate applied disodium octaborate tetrahydrate, a low-toxicity preservative treatment for lumber and plywood, proved to be unsuitable for use in exterior/exposed applications. Water-soluble sodium silicate will leach out of wood and, when it interacts with air, an unsightly white crystalline dust forms on the surface of the treated wood-particularly aggravated by hammer blows.

Additionally, like the new breed of copper-based wood preservative treatments, it proved to be highly corrosive to metals. This month, in part five, we'll conclude this series all about wood preservative treatments with a technology and product that many hope will be the "silver bullet" the construction industry has been searching for since chromated copper arsenic was banned at the end of 2003.

What if?

Sodium silicates, particularly liquid sodium silicate (microscopic particles of glass in an aqueous solution), have been in use for decades as a flame retardant for wood building products. It is also widely used in: laundry detergents, household cleaning products, textile and paper bleaching and as a corrosion inhibitor in water treatment plants. For preserving wood, the problem with sodium silicate is its soluble characteristics.

By dictionary definition, the term insoluble is defined as, "That cannot be dissolved: insoluble matter." But what would happen if sodium silicate could be rendered insoluble?

That's the question environmental chemist and Timber Treatment Technologies LLC CEO Karen Slimak asked herself a decade ago. Slimak's breakthrough/insight was to invent the technological process whereby sodium silicate could be converted to an insoluble form via a chemical/heat-treatment process, which crystallizes the wood structure itself forming exponential layers of microscopic glass particles. Known as sodium silicate technology, TTT patented their two products: TimberSil and TimberSil Plus, claiming SST technology to be:

• Non-toxic

• Non-carcinogenic

• Non-corrosive

• Non-leaching

• Non-dusting

• Fire-retardant

• Arsenic free

• Exclusive of heavy metals

• Resistant to mold and mildew

• Strong

• Durable

• Odorless

• Non-volatile (no VOCs)

For more than 30 years, Slimak, a recognized expert in her field, studied the relationship between health and human exposure to the multitude of chemicals in our environment. The focus of Slimak's research was toxicity, in particular the causes of autism and allergies in humans.

"I'm just terribly, terribly concerned," stated Slimak, "about the chemicals out there in our indoor and outdoor environment."

With the ban on CCA and subsequent problems with the copper-based preservative treatments such as ammonium copper quatenary and water-soluble sodium silicates, Slimak determined that the time was right to introduce SST and TimberSil to the marketplace.

TimberSil is effective even on those species of wood known to be difficult to treat, such as Douglas Fir and Hemlock. The process begins with the wood pressure treated with TimberSil compound then, it is heated in a modified lumber kiln. To help easily distinguish it from other treated wood products and for job site inspection, potassium permanganate is added giving TimberSil treated wood a distinctive brown coloration.

Currently, two versions of TimberSil are available:

• Standard TimberSil: Suitable for interior applications, such as sill plates and interior framing.

• TimberSil Plus: Rated for exterior use (including ground contact). It has a higher concentration of sodium silicate and includes a 40-year warranty covering biological degradation/termite infestation/damage in both exposed and in-ground applications.

Standard TimberSil is used in regions, like the gulf and southeastern states, where protection from the dreaded formosan subterranean termite is required. Standard TimberSil includes a 40-year warranty for interior use, one year for outdoor use. Compared to ACQ or copper azole, TimberSil is price-competitive costing slightly less than either of the copper-based treatments.

Though it is not yet listed, TTT is seeking International Code Conference recognition by mid-2005. Believing that the American Wood Preservers Association lacks objectivity concerning its longstanding relationship with the chemical industry, TTT chose the same route the manufacturer of EnviroSafe Plus took: appealing directly to local code officials for independent approval. However, unlike EnviroSafe Plus, TTT is simultaneously seeking listing for TimberSil with the ICC. As mentioned in part four, building codes typically contain a clause allowing building officials to approve the use of new, non-code listed products in their jurisdictions.

TimberSil relies on a mineralization process rather than chemical toxins to prevent infestation and decay by shutting down the food source for: termites, carpenter ants, microorganisms, etc. Sodium Silicate (NaSiO2) is also known as "water glass." Chemically, it is similar to Potassium Silicate, which is widely used in mineral silicate paints both for its durability and low-level of off-gassing volatile organic compounds.

Hurry up and wait

Until TimberSil is listed with the ICC, support/approval by local code officials is crucial in providing TimberSil a place in the market for wood preservative treatments. In discussion with code officials in several states at the time of this writing, TimberSil is currently approved for use in several counties in southwest Florida and part of South Carolina. Applicable to decks, sill plates, outdoor structures, playground equipment etc., it is also finding a use with many window manufacturers (there are 6,500 window manufacturers in the U.S.). Unlike ACQ and/or Copper Azole, which bleed through paint and are highly corrosive to metals, TimberSil accepts stains and paint well and is available in a clear version for finishing.

TimberSil's workability characteristics are nearly identical to untreated wood. Though sodium silicate can be used as a flame retardant, TimberSil, though it could with a modified formula, does not carry a Class 1 fire-rating presently.

Starting in 1995, TTT has been conducting tests inclusive of placing pieces of TimberSil treated wood in termite mounds for months at a time-no damage to the test pieces was observed. Accelerated UV testing is underway without definitive results thus far.

Timber Treatment Technolgies (located in Grosse Point Farms, Mich.) with its sodium silicate technology and line of TimberSil products, may just be the silver bullet the construction, fastener and connector industries have been searching for since the health and environmental problems associated with CCA surfaced in the 1990s. Because it is a viable alternative to Copper-based and/or Borate-based wood preservative treatments, releases minimal pollutants, reduces the need for pesticides and is a durable, low-maintenance product, TimberSil made the GreenSpec Directory's "Top10" list for 2004. Published by BuildingGreen Inc. (www.BuildingGreen.com), publisher of the well-respected, advertisement-free built environment newsletter Environmental Building News, receipt of such an honor bodes well for TimberSil as the "heir apparent" to CCA as the wood preservative of choice for the foreseeable future. Learn more about TimberSil at www.TimberSil.com.