Solution
New support posts for the poles needed to be installed, including three that had been replaced in earlier work projects. Of greater concern, however, was choosing an appropriate method of treating the carvings along the pole to reduce water penetration and fungal decay. Three treatment goals were identified:
To provide effective protection for above-ground wood while
minimizing hazards to both applicators and the environment.To utilize a treatment as "reversible" as possible in the event of
unforeseen problems or the availibility in the future of improved preservation treatments.To minimize changes in the appearance of the wood.
After investigation of various possible techniques, the decision was made to apply a borate preservative followed by a water repellent coating.
Borates. The prime advantage of using borate preservatives rather than other preservatives is that they are effective against brown rot and white rot fungi and most wood-destroying insects while being relatively safe for both users and the environment. Borate is a generic term for boron compounds containing the element oxygen. Boron is very toxic to most decay fungi and insects that commonly damage wood, including carpenter ants, most wood-destroying beetles and termites.
While it penetrates wet wood better than dry wood and is used more commonly as a preservative for unseasoned wood, commercially available mixtures of borate and ethylene glycol provide protection even for seasoned wood. Aided by the ethylene glycol, (a thick liquid alcohol), the borate solution diffuses into the wood, with greater penetration of the outer areas and also into moist areas.
The ethylene glycol used in commercial preparations will evaporate in a short time. Thus the mixture will wet and briefly darken freshly treated wood. However, this discoloration will usually evaporate within a few days. After the glycol volatizes, the treatment will not affect subsequent painting, staining or the gluing of wood (appropriate glues must be used). In addition, borate compounds are not corrosive to most metal fasteners, although aluminum and galvanized metal may be affected. Borate penetration of wood can be readily detected by use of an applied color test for boron, but it does require slicing off a section of the wood. The work with the totem poles involved removing an underground butt section, treating it with borate and water repellent, and placing it outdoors to serve as a test.
There are some disadvantages. Borate compounds are not effective in controlling mildew fungi or soft-rot fungi. Borates are water soluble and may leach out of the surface when exposed to frequent wetting. Borates also are not as effective for applications on wood that will be used below grade, unless formulated with a co-biocide and protected from leaching. For above-grade, unpainted wood, subject to frequent wetting, a stain, paint or water repellent coating is desirable after treatment with borate preservatives. (The fact that borates are water soluble does provide for "reversibility" if there are unforeseen problems in the future.) During applications, care must be taken to protect nearby vegetation since borates are nonselective herbicides and are toxic to plants. Finally, the borate solution does not penetrate when applied to painted surfaces.
Water Repellent. It was decided that a water repellent with a mildewcide additive should be applied, after treating the totems with a borate wood preservative. A commercially available paraffin oil based water repellent was selected. According to the manufacturer, the paraffin oil penetrates the wood to form a water sealant while the soybean oil, reacts with oxygen and hardens to bond with surface fibers of the wood. The selected water repellent included in the mixture the mildewcide Busan 1009R which is classified as a low-toxic chemical and has an odor that will dissipate in about a week's time.
Application of a water repellent was considered necessary since frequent wetting of the poles would result in the borates leaching out of the unpainted wood. The mildewcide was used to reduce staining from mildew growth on the carvings. Like most water repellents, this one also caused some darkening of the wood. This was considered but some darkening was deemed acceptable, particularly since it will lighten over time. Since the effectiveness of most water repellents diminishes with age, reapplications to the totem poles will probably be needed approximately every 3 years. Samples to be taken from the test log in the future will help determine when reapplication of the borates may be needed.
Pole Preservation Procedures. The weather and work conditions necessitated that the project be done in two phases. Four poles were done in the first phase. Using a large crane and other equipment, the 1 to 2 ton totems were cut off at the decayed bases and removed to a covered area.
The poles were then cleaned, using brushes to apply denatured alcohol in water in a 50/50 mixture. This was done to remove lichen, moss, and mold that was widespread at the top and at the base. Support posts were detached by removing the 1/2" all-thread steel rods that had connected the posts to the carved poles. The totem poles then were cleaned with water using natural bristle brushes and a garden hose with a spray attachment. Since the red cedar poles had been exposed to rain, the use of water to clean them didn't present any problems.
Small pockets of decayed wood were removed from the totems. These usually occurred near the base and where the totem poles abutted the support posts at the back. Most of these pockets were small enough that patching with new wood was not warranted. All the totems had checks and splits, some as wide as one inch. Over the years, many had been filled with a variety of materials, including Plaster of Paris, wood shims, and wood filler compounds. Others were untreated but had collected organic matter. These filler materials had not moved with the old wood as it expanded and contracted. Thus, much of the filler material thus had separated from the wood, allowing retention of moisture that seeped in behind it. Each filled crack or split was first documented and, in most cases, the filler was removed, using compressed air, brushes, spatulas, and other small implements.
Small cracks and splits were similarly cleaned. Borates and water repellents were used to retard water penetration and provide protection from insects and fungal decay. Large splits and cracks were handled differently because of a possible loss of structural integrity. They were filled with a flexible epoxy, fumed silica and micro-balloon mix, and then covered with an oil stain to blend with the adjacent old wood. The water repellent coating was then applied over the oil stain. In some instances where wood had been inlaid and recarved during earlier repairs, reattachment of these patches was done using an epoxy adhesive. (Future repairs with adhesives would require removal of the water repellent coating using a solvent since most adhesives do not bind to wood coated with a water repellent. Most exterior adhesives, however, will bind to wood treated with borates).
Following repairs, the poles were first treated with a commercially available borate preservative. It was purchased as a concentrate and diluted with warm water in a 1:1 mixture in accordance with label instructions. With the pole on its back, supported by cribbing and padding, the ends were treated with a brush application of the preservative as well as with any end grain exposed by carvings. The preservative was then sprayed onto the rest of the pole using a 2-gallon garden sprayer. This was followed by a second coat, spraying slowly to ensure all cracks and crevices received ample coverage. The poles were sprayed until thoroughly wet and rotated with a chain hoist as needed. Near the surface, where wood was oversaturated with the preservatives, boron salts fluoresced on the surface after the glycol and water evaporated. The florescence was removed by wiping with a wet brush. After waiting several days for the surface to dry from the application of the wood preservative, water repellent and mildewcide mix then was sprayed onto the pole, again using a garden sprayer to apply the mix and a brush to spread it.
Support Posts. Each of the totems needed to be fitted with a new support post. The support system selected consisted of a yellow cedar log, each engineered to size, that extended above and below grade. The yellow cedar log was shaped to fit against the concave back of the totem and bolted to it with fiberglass all-thread rods, thereby providing lateral support. Yellow cedar was chosen for the replacement bases. Yellow cedar was readily available in the required sizes and has a decay resistance similar to red cedar. Pressure-treated logs meeting project requirements were not commercially available in the Sitka area. Since the greatest deterioration would be at and below grade, a preservative treatment that could be applied in the field was necessary to facilitate future reapplications. Since major deterioration had occurred in the red cedar bases from the ground to 18" below grade, some additional protection was needed in the corresponding area of the new yellow cedar support posts.
After careful study, the decision was made to apply to the bases of the support posts a preservative in paste form that consisted of copper naphthenate and borax. This method had been developed to treat the groundline of utility poles. Copper naphthenate protects the outer layers of wood and is not readily leachable. The borate is not fixed and will move with the moisture in the wood, throughout the cross-section. A prepared bandage, consisting of the paste, applied to a polyethylene-backed wrap (bandage), was stapled to the support post so that it covered the post from of 3" above ground to 18" below the ground.
It was anticipated that the copper naphthenate might migrate up the base about 6" above the bandage, giving a greenish color visible on the support base.
This discoloration was not considered objectionable in the case of the support poles, since most of them at Sitka are already greenish in color at the base from mold and mildew. The utilization of a wrap or bandage was considered the most effective application method and, in addition, it would retard the borate from leaching out of the wood.
It is also anticipated that the wraps will be inspected in 10 years to assess their condition and possible replacement. (This would only require removal of the dirt around the bases to a depth of approximately 20" so that a new wrap could be applied, if needed.)
Upon securing the support post to the totem, the entire unit was re-erected. The prepared bandage was fastened to the support post before the last 20" of fill dirt was added.
Environmental and Health Considerations
The National Park Service favors an integrated pest management program (IPM) approach to pest management. This program maximizes the use of natural controls, when possible, while minimizing chemical treatments. Where chemicals are deemed necessary, it requires that chemicals may be used: (a) only after sufficient monitoring has shown that an injurious level of damage can be expected, if chemicals are not applied and, (b) when the least toxic chemicals are used. (Prior approval for use of chemical preservatives and pesticides may be necessary in organizations that have designated integrated pest management coordinators).
With the decision to keep the poles uncovered and displayed outdoors, experience had shown that effective chemical preservatives were needed in order to provide more long-term protection of the carvings. Since exposed end-grains in the carvings and cracks and splits in the wood were commonplace, the unpainted poles could not be adequately protected by using water repellents alone. Clear repellents would need to be applied on a regular basis and the thoroughness of coverage would be difficult to establish over a long term, thus the need in the case of the totems of both a wood preservative and a water repellent.
Historically, the poles were painted only in selected areas and not in their entirety. No historic paint documentation existed and application of paint as a protective coating over the entire pole was not considered. The borate application was selected as the most effective wood preservative for the totem pole, minimizing changes in appearance, as well as carrying the least safety risks.
In addition to the health precautions provided by manufacturer, nearby vegetation needs to be protected from contact during field re-application because borates are nonselective herbicides. This is accomplished by spreading a trap around the base of the totem to collect the run-off from both the borates and the water repellents with mildewcide.
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