PENCIL MAKING INDUSRTY , WOOD SEASONING AND PRESERVATION

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PENCIL MAKING INDUSRTY , WOOD SEASONING AND PRESERVATION FOR 504 FOREST PRODUCTS – CHEMISTRY AND INDUSTRIES N.KAKAGARAJ 1ST Msc [FORESTRY] FOREST COLLEGE AND RESEARCH INSTITUTE METTUPALAYAM TAMILNADU

PENCIL MAKING INDUSRTY : 

PENCIL MAKING INDUSRTY

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In ancient Rome, scribes wrote on papyrus (an early form of paper) with a thin metal rod called a stylus, which left a light but readable mark. The word pencil comes from the Latin word pencillus which means "little tail". Graphite came into widespread use following the discovery of a large graphite deposit in Borrowdale, England in 1564. HISTORY OF PENCIL

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First , sticks of graphite were wrapped in string. Later, the graphite was inserted into wooden sticks that had been hollowed-out by hand. The wood-cased pencil was born. An Italian couple, named Simonio and Lyndiana Bernacotti, create the first blueprints for the modern carpentry pencil for the purpose of marking their carpentry pieces

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In the late sixteenth century, a method for attaching strips of wood around graphite was discovered in Germany, and the modern pencil began to take form. In 1662 the first attempt to manufacture graphite sticks from powdered graphite was in Nuremberg (Germany) It used a mixture of graphite, sulphur, and antimony.

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In 1795, Nicholas Jacques Conte discovered a method of mixing powdered graphite with clay. Forming the mixture into rods that were then fired in a kiln. By varying the ratio of graphite to clay, the hardness of the graphite rod could also be varied. More graphite - blacker and softer the pencil

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In 1839, Lothar von Faber of Germany developed a method of making graphite paste into rods. He later invented a machine to cut and groove the pencil wood. The early 20 th century - development of colored pencils - graphite core was replaced by a pigments or dyes and a binder. Today, colored pencils are available in more than 70 colors, with 7 different yellows and 12 different blues.

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Outer wood slats Graphite clay core Wood character for pencil making The wood must be able to withstand repeated sharpening Cut easily without splintering Does not warp or lose its shape, and is readily available selected wood should be slat Even and fine textured Free from knots Light in weight but reasonably strong Should have good machining properties Should not warp or chip off during machining Raw materials for pencil

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Not all wood can be used for pencil industry, only the soften one is suit for pencil making, --Cedrus deodara (cedar) - Juniper Virginiana (red cedar) - Calocedrus decurrens(Incense-cedar) - Pinus Sibirica - Pinus Koraiensis - Linden Wood (Basswood) - Alnus Wood used for pencil

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Cotton Wood - Populus deltoides Indian Rose Wood Indonesia Jierdong Juniperus procera (African pencil cedar) Cupressus sp - (himalayan cypress) Aesculus indica - (hourse chestnut) Hymenodictyon excelsum - (kuthan) Lophopetalun wightianum

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linden wood to produce the pencil, it is best one in China Calocedrus decurrens as the premier wood species for high quality pencils worldwide. Juniperus virginiana hich was the premier wood for US produced pencils and some European pencils dating from the mid 1800s .

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Pencil manufacturing process

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Wood logs Pencil blocks Pencil slats Treat with chemical Making grooves in to the slats Fixing of graphite in to the grooves 2 nd grooved slat pasted Compressed Separation of pencil Pencil is painted Flow chart of pencil making

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The logs usually arrives at the factory logs are cut into "Pencil Blocks.“ Pencil Blocks are cut into "Pencil Slats.“ Logs are then sawed into narrow strips called "slats"; These are about Long-7.25 inches (18.4 cm) Thick-0.25 inch (.635 cm) Wide-2.75 inches (6.98 cm) Manufacturing process

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Pencil Slats are treated with wax and stain to prevent warping. A machine cuts grooves into the slats to accept the writing core (lead). Graphite placed into the grooves Writing cores -- made from a mixture of graphite and clay The more graphite used, the softer the pencil, and the darker its line.

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A second grooved slat is pasted on the first slat -- making a "sandwich.“ This is done with a machine called a "lead layer“ where the sandwiches are then "compressed" to hold them together tightly while the glue dries The sandwich is machined into pencil shapes.

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The individual pencils cut from the sandwich are ready for further processing. Any defective pencils such as uncentered leads or chipped wood are discarded at this point. Each pencil is painted. A recess is cut to accept the ferrule(the metal ring that holds the eraser to the pencil). A ferrule and eraser are crimped into place on each pencil.

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Their cores contain coloring materials such as dyes and pigments instead of graphite. First, clay and gum are added to pigment as bonding agents. Then the mixture is soaked in wax to give the pencils smoothness. When the pencils have been formed, the outsides are painted according to the color of the center mixture Colored pencils

Pencil Standard : 

Pencil Standard Diameter -7 mm. Length-18 cm (7.5 in) long. 18 cm long pencil that can draw a line 55 kms long Average write about 45,000 words

Grading & Classification : 

Grading & Classification Developed by Brookman(1900s), an English pencil maker Using "H" (for hardness) "B" (for blackness) "F" (for fine point). The standard writing pencil is graded HB.

Pencil industry shake-out has the stronger in fray : 

Pencil industry shake-out has the stronger in fray Over 14 billion pencils are manufactured worldwide annually Maharashtra-based companies account for 70 - 75 per cent of the pencils manufactured in the country, Delhi-based units make about 10 - 15 per cent. In Tamil Nadu itself, over the last decade more than three units have closed down and just two manufacturers of writing pencil are left in the fray. Friday, Apr 05, 2002

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Wood seasoning and preservation industry

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Freshly felled timber contains roughly 100 percent based on the oven dry weight of wood light timbers the quantity of water in green condition is twice as much as the weight of wood substance ( that is, roughly 200 per cent). A well seasoned piece of wood - 10 to 12 percent average moisture. Impotence and scope

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To ensure that timber products shape and size and to eliminate losses in service through cracking, splitting and warping “seasoning” the timber, that is, to reduce its moisture content to an average equilibrium with the atmospheric condition of the locality of use. This should be in equilibrium with the atmospheric humidity.

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Degree of seasoning is necessary for proper retention of shape and size of component parts. Rough work and for outdoor uses-15 to 20 % moisture content, is considered enough. This also makes preservative treatment easy and effective.

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1. No risk of fungal decay 2. Reduces weight 3. Improvement in Strength Properties 4. Increase in Nail and screw holding capacity 5. improves Gluing capacity 6. Helps in Preservative Treatment 7. Wood exhibits better electrical and thermal Insulation properties Advantages of seasoning

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8.Easy transportation and handling costs. 9.Increases easy impregnation with preservatives. 10. Makes easy and ensures better results in wood working. 11. Minimizes other seasonal defects such as warping, bowing, cracks etc. after use. 12.Ensures more dimensional stability. 13.Enables substantial long-term economy in utilization by minimizing replacement

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Current trends

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India - more than 80 species of wood. Wood drying - not common practices in developing countries like Nepal, India, Bangladesh and others. 6-7 % of the total production of industrial wood produced in India is seasoned in a strict sense (Pandey and Jain, 1992) Nepal, it is estimated far less than India.

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A large quantity of timber used in India is not properly dried. Unseasoned wood- defects like warping, cracking, splitting or decay and insect attack. In Western countries Timber is not allowed to come out from saw mill unless it is seasoned and treated. It is compulsory to season and treat.

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Institute of Wood Science and Technology Wood Seasoning and Preservation Division Bangalore They have also tested Eco-friendly wood preservatives prepared from plant extractives like Cashew Nut Shell Liquid (CNSL) and Neem oil. Copperised neem oil and copperised CNSL treatment gave complete protection against termites and wood .

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CCA is low-cost, highly effective -residential and garden construction, outdoor furniture. CCA has already been limited in over 26 other countries. Most European countries have already limited CCA use with further restrictions being considered. Japan has changed to preservatives that do not contain either arsenic or chromium.

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Substitute for CCA in residential applications: Alkaline Copper Quaternary(ACQ) Amine copper azole (CA) copper xyligen

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In warm weather 1-inch lumber can be dried to 15 or 20 % moisture content in 45 - 60 days. In the winter months, lumber will require twice as long to dry. 15 - 20 % moisture content is adequate for building construction. 6-8 % moisture content for indoor use Drying time

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Air-seasoning

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The air-seasoning of timber Stacking of timber – 15 % moisture Drying is by evaporation &air circulation An open, well-drained site should be selected The foundations - 45 cm above the ground.

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boards is separated by spacing A waterproof covering - protect from sun and weather. Roughly it takes about 12 month for each 20 mm timber-thickness.

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Proper stacking - uniform drying and reduces seasoning degrade. stacking - 2 types 1.Horizontal stacking – This is the most common method of stacking timber for air seasoning and is suitable for all forms of sawn timber. Stacking

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One in nine methods -railway sleepers, close crib method (for slower drying and thick lumbers) open crib method (allowing more air circulation for faster drying) Vertical stacking:  This is done for the rapid surface drying of non refractory woods . The planks stacked should be turned frequently to prevent warping. After the partly drying by vertical stacking, the timber can be air dried by horizontal stacking too

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Kiln seasoning

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Use is "KILN" Most energy intensive amongst wood processing operations The timber is stacked in the chamber. Then with Air blower heat exchanges in chamber at pressure. Timber is kept in chamber for 6 to 12 days as per its fiber property. These removes all possible unwanted moisture through fibers. kiln Seasoning

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The seasoning Kiln is a chamber equipped with arrangements for heating and humidifying The drying air to desired conditions of temperature and relative humidity. Air circulation over the surfaces of timber stacked inside. Fans are used for faster circulation of air.

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Solar kiln seasoning

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Solar drying- twice the time required for kiln-drying, is well Suited to high-grade applications (furniture) Solar-drying is really a slower and gentler form of kiln drying. A number of different configurations have been tried, including a double skinned inflatable kiln. Some kilns developed overseas can generate temperatures of over 40C inside even though the temperature outside is – 20C. Solar kiln seasoning

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Advantages: Does not require a large initial investment Disadvantages yard storage for a considerable time before it is ready for market Advantage Dries the wood in a short time and can provide dry timber for all seasons of the year Disadvantage Drying requires a comparatively large capital investment Air drying Kiln seasoning

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There are two broad categories: 1.defects that arise due to the shrinkage assimilarity. (warping, cupping, bowing, twisting, and spring) 2. defects that arise due to uneven drying. This leads to the rupture of the wood tissue: checks, splits, honey-combing and case-hardening. It is controlled by providing appropriate amounts of heat, air circulation and relative humidity. Drying defects

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Why Chemical Treatment Required ? Wood can destroyed by biodegrading agencies such as fungi, insects, termites etc. An untreated non-durable wood may last from 3 to 10 years. Treatment with effective wood preservatives can increase its life from 12 to 50 years. Thus 4 times greater benefit, which is best comparing to the cost of treatment.

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1- Oil borne preservatives: This is derived from coal and petroleum products. Creosote is still being used for outdoor and in the marine for long period Railway sleepers that are treated with creosote endure 35-40 years creosotes enriched by PCP (pentachlorophenol), copper, arsenic, zinc are also used. Type of preservatives

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2.water soluble preservatives; This chemicals are effectively protect the wood from decay. It is liable to washed away with water Not suitable for outdoor works. Two types A)non fixed water soluble type It is washed by water Used in above ground level works Borax, boric acid, sodium PCP, zinc sulphate, copper sulphate, mercuric chloride, sodium fluride

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B)fixed water soluble type It is not liable to leaching through water Retain the wood for long time. It is colourless,odourless, and non acidic one. CCA(cu,cr,Ar), CCB(cu,cr,B), CCF(cu,cr,F), chromated zinc chloride, zinc meta arsenate, Ammonical copper chromate(ACA)

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All measures that are taken to ensure a long life of wood There are 2 method Wood preservation

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The most common of these treatments involve the application of the preservative by means of Brushing or spraying, Dipping Soaking Steeping or by means of Hot and cold bath applying preservatives in bored holes diffusion processes sap displacement Non-pressure processes

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Sap displacement method

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Round timber and bamboo are kept vertically in the preservative solution for 3-4 days. After some time wood are inverted to get a uniform treatment. This is suitable for water soluble type of preservatives. Sap displacement method

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Permanent method for preserving timber life. it is carried out in closed cylinders with applied pressure and/or vacuum. Advantages : Deeper More uniform penetration Higher absorption of preservative is achieved. treating conditions can be controlled Pressure processes

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Treating conditions can be controlled These pressure processes can be adapted to large-scale production. Disadvantages ; The high initial costs for equipment and The energy costs are the biggest

Boucherie and modified boucherie method : 

Boucherie and modified boucherie method

Boucherie and modified boucherie method : 

Boucherie and modified boucherie method It is similar to sap displacement method. But the preservatives are applied at the end butt at certain pressure. Normally a pressure of 1.06-2.11 kg/cm2 is applied for quick and better penetration of preservatives.

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Full-cell Methods

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wood material is sealed in impregnation cylinder. Preliminary vacuum (lower pressure) is applied to remove the air from cell gaps and walls. After the impregnation preservative is admitted to the cylinder. Pressure is applied until it penetrates into all gaps of wood material Full-cell Methods

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Microwave Conveyor Machines

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This processed wood is not prone to breakage or damage. Automatic in nature, heat evenly and consume less time for processing. The heating and drying of the wood can take place at the same time. Cost effective approach for wood seasoning. Use - furniture industry and flooring industry. Microwave Conveyor Machines

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1. Rapid drying and high efficiency 2. Even drying, wood processed is not easy to yield b break and deformation 3. Insect killing and mold proofing 4. High-efficacy and energy-saving 5. Easy to operate and control 6. Safety and non-pollution Advantages

: 

http://hindustanpencils.com/hppl/intro.aspx http://www.pencils.com/pencil-making-today en.wikipedia.org/wiki/Wood_drying en.wikipedia.org/wiki/Wood_preservation R.K luna (1989) plantation forestry in india (pp 311-312) References

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