Forest Utilisation Chapter 19: Resin Tapping, Turpentine and Rosin, and Charcoal Burning
Forest Utilisation Notes · Chapter 19
Chapter 19: Resin Tapping and Charcoal Burning
Pines tapped in India, cup and lip method, light and heavy tapping, channel sizes and freshening, rill method, distillation of turpentine and rosin, grades and uses, and charcoal making in retorts, pits and kilns.
1. Pines and resin
Pine oleo-resin is a translucent viscous fluid, soluble in alcohol, benzene and ether but not in water. On distillation it gives turpentine (an essential oil) and rosin (a non-volatile solid). The genus Pinus is the only commercial source.
| Pine | Status |
|---|---|
| Pinus roxburghii (chir) | The only species regularly tapped; outer Himalaya and Siwaliks at 450 to 2300 m, Kashmir to Bhutan |
| Pinus wallichiana (kail, blue pine) | Superior resin, but in remote areas; uneconomic to extract |
| Pinus kesiya (khasi pine) | Good resin, limited distribution |
| Pinus gerardiana (chilgoza) | High, inaccessible localities; not feasible |
Systematic tapping began towards the end of the 19th century, in Jammu and Kashmir, Himachal Pradesh and Uttar Pradesh. Chir forests cover about 0.9 million ha; crude resin output was about 48,000 tonnes a year.
2. Cup and lip method
Resin lies in vertical ducts in the wood and horizontal ducts in the rays. A shallow wound stimulates flow, which is greatest at the top of the incision. India long used the French 'cup and lip' method.
| Kind of tapping | Rules |
|---|---|
| Light continuous tapping | Trees above 0.9 m girth. 0.9 to 1.8 m girth: one channel; above 1.8 m: two channels. Each channel worked for 5 years, then a new one is started anticlockwise, leaving an interspace. Gives sustained yield without harming vitality |
| Heavy tapping ('tapping to death') | As many channels as the tree can bear with a minimum interspace of 10 cm. Begun 5 years before main fellings in regeneration areas and 2 years before thinnings. Lowest girth 60 cm |
| Item | Size or timing |
|---|---|
| Enumeration | Every 5 years; a section has about 1000 channels per tapper; a depot unit 25,000 to 30,000 channels |
| Bark scraping | 15 cm wide, 60 cm long; first channel on the south or south-west face |
| Initial channel | 10 cm long, 10 cm broad, 1.3 cm deep |
| Final depth | Not more than 2.5 cm in light tapping |
| Lip | Galvanised iron, 15 × 5 cm, below the blaze |
| Pot | About 15 cm deep, hung on a nail 2.5 cm below the lip, with a lid |
| Fire precaution | Clear 1.2 m around the base; controlled burning in chir forests |
| Freshening | Early March to early November; 5 a month (every 6 days); each freshening at most 1 cm high |
| Channel length after a season | About 48 cm; grows about 38 cm each later year |
| Yield | 2 to 4 kg per channel a year |
Acid stimulants (sulphuric acid, or a 20% solution of sulphuric and nitric acids in equal parts) raise yield by 7 to 50%. A tapper freshens about 167 channels a day. Resin is collected into 18 litre tins holding about 20 kg.
3. Rill method (FRI)
The cup and lip method gave poor control of blaze depth and wasted timber. FRI developed the rill method, which keeps the bole round and loses no timber.
- Bark shaved over about 45 × 30 cm, starting about 15 cm above ground.
- A central groove is cut; rills (V-shaped cuts) are made on both sides with a freshening knife.
- Rills are 6 to 7 mm wide and about 2 mm deep into the wood, with 5 mm of bark left between rills.
- Freshening weekly; a 20% solution of sulphuric and nitric acid (equal parts) is sprayed on each fresh rill.
- The blaze rises 35 to 38 cm a season and is worked upwards for 5 years; then a new blaze is started at the bottom, leaving 7.5 cm space.
- Claimed to give about 22% more resin, no scrap resin, no loss of turpentine and no loss of timber.
4. Turpentine and rosin
| Product | Yield and facts |
|---|---|
| Turpentine | 17 to 20%; colourless, strong odour; boiling point 155°C; SG 0.85 to 0.88; a mixture of terpenes; 2 grades |
| Rosin | About 74%; SG 1.08; melts at 100 to 140°C; graded by colour (pale, medium, dark) into 12 grades |
| Impurities and water | 6 to 9% |
Factories: Bilaspur and Nahan (Himachal Pradesh) and the Indian Turpentine and Rosin Factory at Clutterbuckganj (Bareilly, UP).
Paints, varnishes, shoe polish, chemicals and pharmaceuticals; synthetic camphor, insecticides, germicides.
Soap making and sizing paper; linoleum, sealing wax, oil cloth, paints, varnishes, inks, soldering, violin bows.
5. Charcoal burning
Charcoal burning is a form of destructive distillation: wood is burnt out of contact with air, so it is only partly burnt (carbonised), and the residue is charcoal.
| Method | Notes |
|---|---|
| Retorts | Closed retorts, by-products recovered (as at Bhadravati) |
| Open pits | Very wasteful; quick charcoal for urgent, limited needs; poor quality |
| Kilns | By far the most widely used |
| Kiln | Features |
|---|---|
| Paraboloidal over-ground | Ideal radius 2.4 to 3 m, height about 2.4 m, 25 to 35 m³ stacked; covered with turf then wet earth; 7 to 10 days; a clear blue flame shows carbonisation is complete |
| Oven kiln | Like the paraboloidal kiln, but its baked mud crust is kept permanently; sometimes brick-lined |
| Pit kiln | About 3.6 × 1.35 × 1.35 m; billets horizontal; carbonisation in about 48 hours, when bluish smoke appears |
| Prismatic kiln | Rectangular base, 4 to 6 m long; takes long pieces stacked horizontally; good charcoal but low out-turn |
| Hill kiln | Cut into a hillside at about 60°; burning uneven |
| Portable metal kiln | Metal plates replace earth; easily moved; higher out-turn and better charcoal; costly |
Good charcoal is black, glistening, porous but fairly hard, gives a clear metallic note, has no taste or smell, low ash and moisture, lights easily and burns without smoke or sparks. It is bulky and does not stand long transport; store in damp-proof, ventilated godowns.
6. Quick revision
- Chir is the only pine regularly tapped. Turpentine = volatile oil; rosin = solid residue.
- Light tapping: 0.9 to 1.8 m girth one channel; over 1.8 m two; each channel 5 years.
- Heavy tapping: 10 cm interspace; 5 years before main felling, 2 years before thinning.
- Channel 10 × 10 cm; final depth up to 2.5 cm; freshen every 6 days, March to November.
- Rill method (FRI): rills 6 to 7 mm wide, 2 mm deep; acid spray; 22% more resin.
- Yields: turpentine 17 to 20%, rosin 74%. Factories: Bilaspur, Nahan, Clutterbuckganj.
- Charcoal = wood burnt out of contact with air. Kilns most used; blue flame marks completion.
7. Interactive MCQ Quiz
18 questions. Tap an option to see the answer and explanation, then go to the next question.
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