How to keep wooden furniture away from wood borers

How to keep wooden furniture away from wood borers

Why Copper

Copper is an essential micronutrient for most living cells. In larger doses though, the copper ion demonstrates activity as an algaecide, bactericide, fungicide, insecticide, and moldicide. Presently copper compounds are used for algal control, wood treatment, antifouling pigments, and crop fungicides (Richardson 1997). The fungicidal properties of copper were recognized in the 1700s, and copper-based preservatives have been widely and successfully used for more than a century. Although borates and organic biocides are gaining importance, copper remains the primary biocide component used today to protect wood used in ground contact or fully exposed to the weather (Lebow et al. 2004). Copper is needed against this challenge since very few organic molecules (other than creosote and penta) possess activity towards soft rot fungi (Hughes 2004). The volume of wood products treated with copper-based preservatives grew exponentially during the 1970s and 1980s and remains high today. Copper compounds also have advantages: it is relatively easy to create waterborne formulations; it is easy to analyze and determine penetration in wood, and copper slows photodegradation by UV radiation and water (Archer and Preston 2006). The focus on copper-based preservatives has increased following concerns about environmental effects of chromium and arsenic and resulting restrictions on the use of chromated copper arsenate (CCA). Much of the early work on copper-based formulations forms the basis for the ammoniacal and amine copper-based systems currently in the marketplace as CCA replacements (Preston et al. 1985). These formulations include quats or azoles as co-biocides. Recently micronized copper formulations with the same co-biocides have come into use. The drawbacks on use of copper compounds include: copper tolerance exhibited in a number of fungal species, possible corrosivity to metal fasteners and aquatic toxicity (Archer and Preston 2006). This paper presents a discussion on copper issues such as the mode of action, problems of copper tolerance, replacements for CCA, the latest micronized formulations and environmental effects of copper-based preservatives.

Copper Azole

Copper azole preservative (denoted as CA-B and CA-C under American Wood Protection Association (AWPA) standards) is a major copper based wood preservative that has come into wide use in the USA, Europe, Japan and Australia following restrictions on CCA. Its use is governed by national and international standards, which determine the volume of preservative uptake required for a specific timber end use.

Copper Azole is similar to ACQ with the difference being that the dissolved copper preservative is augmented by an Azole co-biocide instead of the quat biocide used in ACQ. The Azole co-biocide yields a Copper Azole product that is effective at much lower retentions than required for equivalent ACQ performance.

It is marketed widely under the "Wolmanized" brand in the US, and the "Tanalith" brand across Europe and other international markets.

The AWPA standard retention for CA-B is .10 pounds per cubic ft (pcf) for above ground applications and .21 pcf for ground contact applications. Type C copper azole, denoted as CA-C, has been introduced under the Wolmanized brand. The AWPA standard retention for CA-C is .06 pounds per cubic ft (pcf) for above ground applications and .15 pcf for ground contact applications.

The copper azole preservative incorporates organic triazoles such as tebuconazole or propiconazole as the co-biocide, which are also used to protect food crops. The general appearance of wood treated with copper azole preservative is similar to CCA with a green colouration.


Other copper compounds
These include copper HDO (CuHDO), copper chromate, copper citrate, acid copper chromate and ammoniacal copper zinc arsenate (ACZA). The CuHDO treatment is an alternative to CCA, ACQ and CA used in Europe and in approval stages for United States and Canada. ACZA is generally used for marine applications.

New Generation ACQ

Alkaline copper quaternary
Alkaline copper quaternary (ACQ) is a preservative made up of copper, a fungicide, and a quaternary ammonium compound (quat), an insecticide which also augments the fungicidal treatment is a wood preservative that has come into wide use in the USA, Europe, Japan and Australia following restrictions on CCA. Its use is governed by national and international standards, which determine the volume of preservative uptake required for a specific timber end use.

Since it contains high levels of copper, ACQ-treated timber is five times more corrosive to common steel, according to test results. It is necessary to use double-galvanized or stainless steel fasteners in ACQ timber. Use of fasteners meeting or exceeding requirements for ASTM A 153 Class D meet the added requirements for fastener durability. The U.S. began mandating the use of non-arsenic containing wood preservatives for virtually all residential use timber in 2004.

Modern versions have been developed which offer improved performance to those mentioned above. It should be noted that the American Wood Protection Association (AWPA) standards for ACQ require a retention of 0.25 pounds per cubic ft (PCF) for above ground use and .40 pcf for ground contact.

ACA

Ammoniacal Copper Arsenate (ACA): water-borne fixing type:
The formulation consists of copper sulphate and arsenic trioxide
dissolved in ammonia. It gives high degree of protection and better
penetration due to the presence of ammonia, which swells in the bamboo
structure

CCA and CCB

Copper Chrome Arsenic (CCA): water-borne fixing type:
It is a heavy duty broad spectrum preservative patented as AsCu; the
formulation consists of arsenic pentoxide and copper sulphate with
sodium dichromate as the fixative in the ratio 1:3:4. CCA has been found
to provide protection for 50 years or more. Due to the arsenic component
only exterior applications are recommended. Though no study has
revealed adverse effects due to exposure to treated products, it must
nevertheless be handled with special care.

Copper Chrome Boron (CCB): water-borne fixing type:
It is a broad spectrum preservative containing boric acid, copper sulphate
and sodium dichromate in the ratio 1.5:3:4. It is a good alternative to
CCA but less effective with a lower degree of fixation, of the Boron
component.

Zin and Penta

Zinc Chloride/Copper Sulphate: water-borne non-fixing type: These
are single salts and offer limited protection. They are highly acidic and can
cause corrosion of metal fittings. Zinc Chloride is highly hygroscopic and
treated bamboo will give a wet look in rainy season. This can adversely
help paints and other finishes.

Sodium Penta Chloro Phenate (NaPCP): water-borne non-fixing
type: It is basically a fungicide. It is also applied with boric borax for
protection during shipment and storage of green bamboo. But due to its
toxic nature it has been banned in several countries. It is the most
effective chemical to prevent moulds and blue stain fungi.

Boron Preservatives

Boron containing compounds: water-borne non-fixing type:
These are usually a mixture of boric acid:borax. Readymade formulation
(disodium octaborate 1:1.4) is also available. Boron salts are effective
against borers, termites and fungi (except soft rot fungi). High
concentration salts have fire-retardant properties. They are not toxic and
can be used for treating bamboo products like baskets, dry containers, etc.
which come in contact with food products.

Different types

Water-soluble salts are dissolved in water. On treatment, the water
evaporates leaving the salts inside the bamboo. These are further
categorized into non-fixing and fixing types.

These are leachable solutions and their use is restricted to bamboo used in
dry conditions and under cover. Bamboo treated with these preservatives
should not be exposed to rain or ground contact. Common example:
Boric acid: Borax & copper sulphate

These formulations are proportionate mixtures of different salts which
interact with each other in the presence of bamboo/wood and become
chemically fixed. In principle, the degree of fixation and efficacy depends
upon the nature of the components and their combination. For example,
Chromium is responsible for fixation, copper is effective against decay
fungi and soft rot and the third compound acts against insect and fungus.
The process of fixation requires some weeks during which the material
should be stored under cover. Slow fixation is preferred in case of bamboo
as it allows diffusion and better distribution of preserving salts.
Common example: Copper-Chrome-Boron, Arsenic Pentoxide & Boric
Acid

Coal tar and creosote available from coal is a dark brown viscous liquid.
Creosote should be used exclusively for pressure processes or hot and cold
treatment. Being oily, it imparts water repellence to the treated material. It
is effective against fungal and insect attack. Due to its dark brown colour
and bad odour, its use is restricted to exterior applications, especially in
contact with mud/ ground

These are slightly more expensive preservatives where the organic solvent
acts as a carrier for toxic molecules and later evaporates, leaving the active
ingredients behind. They are available commercially in ready-to-use
forms. A good formulation is an appropriate mixture of fungicides and
insecticides. There is little change of colour of the treated material but a
residual odour may remain for some time. The method of use will be
recommended by the manufacturer. Formulations available in
concentrates are more economical to use.
Common examples: Trichlorophenol (TCP) and Copper/Zinc
napthenates (metallic soaps) are used as fungicides. Lindane/
cypermethrin is used as an insecticide.

Some naturally occurring materials can prevent decay to some extent.
Long-term protection is not possible through these preservatives.
The Giant Indian Milkweed is deadly to beetles and fungi. Boiling of slivers
with fresh leaves and stem of this plant for 30-60 minutes will prevent
attack.

Types Of wood Preservatives

Water-Borne Types

Non-Fixing type preservatives

Fixing Type preservatives

Oily Preservatives: Creosote

Light Organic Solvent-based Preservatives (LOSP)

Natural Toxicants

What is wood preservation

The term wood preservatives defines that the wood preservation is the process of preserving wood from the wood destroying agents like insects or fungus so that the life span of the wood can be extended. It refers to the treatment of wood with chemicals to impart resistance to degradation and deterioration by living organisms. The proper application of chemical preservatives can protect wood from decay, and stain fungi, insects and marine borers, thus prolonging the service life of woods for many years.

The wood contents celluloses, hemicelluloses, starches and other susceptible materials that attract the fungi and insects to be degraded and eaten. After the preservative treatments, the fungi and insects cannot decompose and feed on these substances, hence the durability of wood is to be increased.

Wood Preservation

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