Liquid should cover the wood surface thoroughly to fill checks and depressions in the wood. Rough lumber may require 10 gallons of liquid per 1, square feet of surface; less for finished lumber. A second application, made after the first has dried is desirable. Wood treated in this manner and used in contact with soil may be protected for 1 to 5 years. Dipping consists of immersing wood in a preservative solution for several seconds to several minutes. It allows better penetration into checks and cracks of wood but is unsatisfactory for uses subject to abrasion.
There is little protection against termites and it is not recommended for wood used in contact with the ground. Cold soaking well-seasoned wood for 2 to 7 days in a vat containing a low-viscosity oil-borne preservative is simple and relatively inexpensive. It is thought to give more protection than dipping. Either green or seasoned wood can be steeped for several days in a tank full of water-borne preservative.
Penetration and retention varies depending on the types of wood and treatment conditions. Thermal process treatment consists of immersing wood alternately in separate tanks containing heated and cold preservative, either oil- or waterborne or in one tank which is first heated than allowed to cool. During the hot bath, air in the wood expands and some is forced out. Heating improves penetration of preservatives. In the cold bath, air in the wood contracts, creating a partial vacuum, and atmospheric pressure forces more preservative into the wood.
Prepare the wood by dusting off any dirt or debris. Use a clean, dry towel or rags to wipe off the wood. Note and repair any imperfections or flaws in the wood. Select an oil or commercial product. There are many available oils and wood preservation products suitable for home use. Follow this advice to select the best one for your wood: Tung oil gives good protection, if you can accept the high price and hours of drying time.
Avoid the last two if nut allergies are an issue. Boiled linseed oil "BLO" is a common choice, but provides poor water resistance and yellows over time. Its main advantage is price. Gather materials. Find a clean, dry rag for rubbing in the oil, and newspaper to catch spills. Because many of these oils are flammable, keep a metal container nearby to store these materials after the oiling.
Have access to water or a fire extinguisher so you are ready in the unlikely event that some of these materials spontaneously ignite. The flammability is greatly reduced once the oil dries.
When the job is finished, air-dry the rags and newspaper in a single layer away from buildings and heat. Mix in solvent if appropriate. Commercial products may not require this step; refer to the label. If using tung oil or linseed oil, mix a small amount of the oil with an equal amount of turpentine, mineral oil, or other solvent. Mix in more solvent if the oil won't penetrate the wood. Never use solvent for cutting boards or other wood that will come into contact with food.
Rub the oil in slowly. Use the cloth to rub the oil into the wood, covering the entire surface. For the most consistent results, dab the oil on one splash at a time, rubbing it across the wood bit by bit. Applying more oil at once is acceptable if you'd like to save time. The more you rub in at once, the more variation there will be in color and shine, but this isn't likely to ruin your wood's appearance.
If you are using a product sold as a wood protector, refer to the label for more precise instructions. Wipe up excess oil. All excess oil should be wiped from the surface within a few minutes, unless your product label states otherwise. The oil that soaked into the wood will provide the protection; excess surface oil will only add an unnecessary surface layer that may become gummy or discolored with time. If the oil has already dried on to the surface, wet a cloth with a little more oil to wipe it up again.
Apply more coats, sanding in between. At least two or three coats of oil are recommended for long-term preservation. Follow these steps each time: Wait until the previous coat is dry. This can take under an hour for some synthetic products, to a week or longer for raw linseed oil. Sand the surface lightly. Mix more oil-solvent mix, if necessary. Use less solvent for each coat, making a thicker and thicker mix. Rub in the next coat. Part 2. Consider applying additional protective products.
Once the last coat of oil is dry, the wood should be much more resistant to decay and weakening. There are some dangers oil does not protect from, however, and these can be handled by an additional finish once the last coat of oil is completely dry. All of the following are optional:. You can use a "wood preservative" to add pesticide and fungicide.
Halogenated compounds such as chloronaphthalenes, chlorinated paraffins and bromophenols can be used with incorporated catalysts, like antimony oxide. Surface coatings: Surface coatings prevent flames spreading across the surface. These coatings are used in gymnasiums, hospitals, hotels, museums, restaurants, kitchens and laboratories. Intumescent coatings: When exposed to fire, these coatings soften and generates non-flammable gases.
The coating trapping the gases bubble and produce a foam. Then the fire retardant solidifies to insulate the surface from the fire. Non-intumescent coatings: Some of them are formulated with materials which chemically interfere with the reactions of burning.
Others based on silicates or borates melt in the fire and form a protective glassy film. Anti-stain Chemicals: Formulations of normal wood preservatives do not give a good control over sapstain fungi and superficial moulds that are responsible for staining in green wood and under coating systems in service.
Sodium pentachlorophenate is found for use as an efficient chemical in spite of its high toxicity. Some co formulations based on sodium pentachlorophenate and borax have been used widely and the most popular consists of one part sodium pentachlorophenate and three parts borax. Pentabor has half the water of crystallisation removed in order to decrease the cost of transport. Trihalomethylthio compounds were also found efficient. Folpet Fungitrol 11 has proved is very active. The Madison formula with a pigmented and water-repellent composition was used as an anti-stain product.
The water-borne wood preservatives, resist leaching during service. Copper naphthenate resists also leaching because of relatively insolubility in water. The most rapid leaching occurs within the first months of service and is greatest in products with high retention levels and high proportions of exposed surface area.
Leaching is increased by exposing the wood to high water flow, low pH and water soluble organic acids. Debarking: Some mills use water jets working at high pressure, the others use mechanical peeling. Machining: All handling of wood by hand or machine should be carried out before preservation process. First of all, the wood to be treated is machined to the required dimentions and the surface is handled in such a way that the wood is ready for treatment.
Steaming: Steaming of timber in steaming vessels of plants enhance considerably the permeability of wood. Incising: Incising is making small slits or incisions in the wood of difficultly impregnable tree species to provide the penetration of preservation solution along the grain in two directions.
Compression: Wood is passed through heavy rollers and the structure of compressed wood is changed to some extent that preservative liquid penetrates easily and uniformly. Ponding and sprinkling: Ponding and sprinkling enhance the absorption of preservative with the dissolution and enlargement of the pits by bacterial activity. Osmose method: The method used widely is osmose method. Highly water soluble and concentrated product is applied to the debarked surface of freshly felled and wet wood, generally poles.
Poles are covered with an impermeable covering for months to allow the diffusion process go successfully. The formulation applied for pine, spruce and fir contains water, NaF, dinitrophenol, starch and adhesive. Boucherie method: The well-known sap displacement method is applied to the freshly-felled unbarked poles.
The capsules put on the thicker end of the boles are connected with pipes to a tank containing 1. The preservative flowing from the tank at a higher place to the capsules takes place the sap of the boles in a few days. Brushing and Spraying: Brushing and spraying are the simplest methods for applying preservative chemicals. Only surface penetration of mm can be achieved.
Deluging: This is a treatment for sawn timber. Organic solvent preservatives is flooded over the wood surface while the timber is passing slowly through a short tunnel. Immersion: Immersion is a treatment of dipping timber in a tank containing preservative for from seconds to weeks. The application gives better results with higher diffusion rates than brushing, spraying and deluging. Short periods of immersion are ideal for treatments of joinery components.
Hot preservative is pumped into the tank until the poles are completely immersed in the preservative solution for a period of six or longer hours.
After the preservative is pumped from the treatment tank to storage tank the tank is flooded immediately with cold preservative solution. The cold solution brings about a partial vacuum in the wood cells and therefore more impregnation of the wood. High-Pressure Treatments: These are the most successful methods in wood preservation.
Wood is treated with chemicals under high pressure in steel pressure wessel. This considerably reduces the overall treatment time, and the finished product is lighter in both weight and color. However, it is not critical that all the water be removed from the wood prior to treatment, as PEG is soluble in both water and alcohol. Alcohol treatments save time but are less cost-effective and always pose the risks inherent in heating alcohol.
Since all alcohols are fungicidal, no fungicide is required when using alcohol in PEG solutions. Before a decision is made to conserve wood with PEG, it is important to consider the fact that PEG is corrosive to all metals, especially iron. For this reason, PEG treatments should not be used on wood that will be in contact with any metal e.
Treating small waterlogged wood artifacts with PEG in the laboratory is a simple and straightforward process. Small vats stainless steel or glass are readily available and they can be placed in a thermostatically controlled oven to maintain the correct temperature; furthermore, only a small amount of PEG is required.
In contrast, when large pieces of wood are treated, there is a considerable investment in PEG sometimes measured in the tons. A substantial vat must also be constructed with the capability to heat and circulate the solution. Laboratories that intend to conserve large pieces of waterlogged wood must be prepared to make major investments in both equipment and chemicals. Of all of the wood conservation methods discussed in this section, any of the various PEG treatments with water is the most utilized because of its reliability and low cost.
Setup for treatment of small specimens of waterlogged wood. The procedure is identical to that described for PEG, except that sucrose is used. Wood to be conserved should be carefully cleaned by rinsing in baths of fresh water to remove all ingrained dirt and to remove the bulk of any soluble salts that are present.
Once the wood is cleaned, the following procedure is recommended:. If sugar is selected as the treating medium, refined white sugar pure sucrose should be used.
The brown- colored, coarse-grained unrefined sugar Type A sugar should be avoided, as it is much more hygroscopic than the white. Each time the relative humidity rises, the surfaces of wood treated in unrefined sugar will become wet. This hygroscopicity is analogous to that encountered when using the medium molecular weight PEGs. The Type A sugar-treated wood, however, remains dimensionally stable. Maintaining artifacts treated by sugar in a controlled atmosphere will ensure the continued success of the conservation procedure.
Artifacts conserved with this method require no more or no less care than those treated with other preservatives. This method constitutes an acceptable means of conserving waterlogged wood and is the least expensive of the methods currently available. Sucrose-treated wood, however, has a dull muted color, and small hair line cracks will frequently form on the surfaces. The treatment will produce dimensionally stable wood and is a viable alternative when the overall cost is a major consideration.
The required equipment is the same as discussed above for PEG treatments. This treatment was developed to conserve well-preserved hardwoods that cannot be penetrated by the higher molecular weight PEGs McKerrel and Varanyi ; Bryce et al. To ensure a saturated solution, an excess amount of rosin should be placed in the container. This results in a thick, viscous layer of rosin that will settle to the bottom of the container. The object being treated should be suspended or supported above this undissolved rosin.
Objects cm thick should be left in the solution for four weeks, while objects less than 5 cm thick should be left in the solution for two weeks. These treatment durations are only rough approximations; each piece of wood should be evaluated based upon its own characteristics.
In some cases, when conserving very well-preserved hardwood, the conservator might consider submerging the wood in a 10 percent hydrochloric acid HCl bath after washing the object and before dehydrating the wood in Step 2 above.
Pre-treatment with hydrochloric acid improves the penetration of the rosin into the object by breaking down the organic acids in the wood. Caution must be exercised, however, as hydrochloric acid may result in a checked surface, which is more subject to cracking post-treatment. In addition, hydrochloric acid is supposed to bleach the wood to a more natural or original color, but the bleaching is only temporary and rarely affects the final color of the treated piece.
Hydrochloric acid pre-treatment can also be used to improve the penetration of PEG into wood, although the finished product may be more prone to checking and shrinkage. To make the pre-treatment bath, mix one volume of HCl to nine volumes of water. The duration of pre-treatment is very variable, but objects cm thick should be left in the acid for approximately four days, while objects less then 5 cm should be left in the acid for about two days.
After pre-treatment, it is necessary to rinse the wood in running water for three to five days to thoroughly remove all traces of the acid before continuing to Step 2 above. This pre-treatment is optional and is often eliminated because of the potential damage to the object.
In practice, ethanol is often used instead of accetone as a solvent for the rosin especially when treatment is carried out in a PVC pipe. Room-temperature treatments, both in acetone and isopropanol, are also commonly employed. If room temperature treatments are used, the treatment time is increased considerably to ensure complete saturation of the object with the rosin solution.
The advantages of the acetone-rosin treatment include the fact that treated wood is light in weight, dry, strong, and can be glued and repaired easily. Because rosin does not react with any of the metals, the acetone-rosin treatment can be used on compound wood and metal objects. Disadvantages include the flammability of acetone and the high cost of materials, which make this treatment practical only for small objects.
In addition, the treatment would not be an ideal choice in cases where it is necessary to flex the treated wood i. In general, the only problems that have resulted from using acetone-rosin have occurred when an old solution was used in which the acetone had already absorbed a considerable amount of water from the atmosphere. It is important that dry acetone or alcohol be used.
Despite the inherent dangers of the treatment and the relative expense, the acetone-rosin treatment should be used more frequently by conservators, particularly for small pieces.
This treatment has one of the better success records in wood conservation and produces the most dimensionally stabilized wood after the PEG and Blend treatments but without the hygroscopic problems of PEG Grattan b. If necessary, the wood should be cleaned prior to treatment. The waterlogged object is first immersed in successive baths of alcohol until all the water has been replaced by the alcohol. Isopropanol or ethanol is usually used. This is followed by successive baths of acetone.
If necessary, the dehydration progress can be monitored by measuring the specific gravity of each bath. When all water has been replaced by acetone, the object is immersed in successive baths of dimethyl ether to replace all the acetone with ether.
When this has been accomplished, the object is dried very quickly by placing it in vacuum to rapidly volatize the ether. Ether is used because it has a very low surface tension of 0.
This means that when the ether evaporates, the surface tension forces are so low that there is no appreciable collapse of the weakened cell wall. If desired, percent dammar resin, colophony rosin, or a mixture of the two may be dissolved in the final bath of ether to consolidate the wood and to protect it from warping due to changes in relative humidity.
PVA may be used in place of the resins on some pieces. This method has proved to very successful, producing a very natural-looking wood that is light in both weight and color.
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