Forest Utilisation Chapter 18: Cutch and Katha, Lac Cultivation and Manufacture of Shellac
Forest Utilisation Notes · Chapter 18
Chapter 18: Cutch, Katha, Lac and Shellac
Cutch, katha and kheersal from khair heartwood, country, modified and factory methods, uses; lac insect, hosts, life history, Kusmi and Rangeeni crops, coupe system, pruning, inoculation, cropping, and manufacture and uses of shellac.
1. Cutch and katha
Cutch and katha are obtained by boiling in water the heartwood of Acacia catechu (khair), a tree of tropical deciduous and thorn forests, mainly in riverain tracts. In parts of south India Acacia chundra replaces it.
| Product | What it is | Use |
|---|---|---|
| Katha | Catechin, crystallised out | Eaten with pan; astringent and digestive |
| Cutch | Catechu-tannic acid | Dyeing and preserving; boat sails, fishing nets, calico printing |
| Kheersal | White powder deposited in the wood | Medicine for cough and sore throat |
2. Methods of extraction
| Method | Steps |
|---|---|
| Country method (cutch) | Heartwood chips boiled in earthen pots about 12 hours; liquid concentrated, boiled to a syrup in an iron cauldron, poured into leaf-lined frames; sets into dark brown brick-like cutch |
| Country method (katha) | Thick liquid poured into moulds dug in fine sand, which absorbs the tannic acid and leaves catechin to crystallise as katha |
| Modified method (both together) | Boil chips in tinned copper vessels; strain hot; concentrate; cool slowly and seed with katha crystals; katha crystallises; filter through muslin; mother liquor concentrated into cutch |
| Factory method | Chippers; hot water extraction under pressure in copper vessels; vacuum concentration; refrigerated tanks for about a week; filter presses; tablets dried |
- Country methods are wasteful: making cutch loses the katha, and making katha loses the cutch in the sand.
- Iron vessels must never be used: cutch forms a greenish-brown compound with ferric salts.
- Katha is soluble in hot water but only sparingly in cold, so cooling separates it from cutch.
- Yields: katha 3 to 4% (cottage), about 4 to 4.5% (factory); cutch 10 to 12% of wood weight.
3. Lac
Lac is a resin secreted by the lac insect, Laccifer lacca (now Kerria lacca), as a protective covering while it feeds on the sap of host plants. It is the only resin of animal origin. India produces about 70 to 80% of the world's lac and exports over 90% of it. Lac is grown mainly in Bihar (now Jharkhand), eastern Madhya Pradesh, Bengal, Orissa, Maharashtra, Assam and Mirzapur.
The insect is recorded on over 100 plants, but about a dozen are common hosts. The three major commercial hosts are palas (Butea monosperma), ber (Zizyphus mauritiana) and kusum (Schleichera oleosa); others are ghont, arhar, khair, babul and Ficus. Kusum produces the best quality lac.
Life history
4. Lac crops and cultivation
| Strain | Hosts | Crops |
|---|---|---|
| Kusmi | Mainly kusum | Aghani (harvest January to February) and Jethwi (harvest June to July) |
| Rangeeni | Palas, ber, ghont, arhar | Baisakhi (April to May) and Katki (October to November) |
Rangeeni gives 80 to 90% of India's lac; Kusmi is less but superior. Each strain has two generations, so two crops a year. Improved methods come from the Indian Lac Research Institute, Namkum, Ranchi.
| Practice | Rule |
|---|---|
| Coupe system | Kusum: 4 coupes, each inoculated once in 2 years. Rangeeni hosts: 3 coupes in the ratio 3 : 1 : 3 |
| Pruning | Light; branches over 2.5 cm not pruned; thin branches cut to leave a 45 cm stalk. Palas and ber for Katki: mid-February; for Baisakhi: mid-April. For kusum, cropping itself serves as pruning |
| Inoculation | Avoid self-inoculation; use mature healthy brood lac free of enemy insects at once; sticks 15 to 30 cm tied on the upper side of branches; one stick gives settlement over 15 to 20 times its length; remove brood sticks soon |
| Cropping | Harvest when mature, within a week of larval emergence, fully |
| Stick lac | Lac scraped from twigs; dried in layers 10 to 15 cm thick |
5. Shellac
- Properties: insoluble in water, soluble in cheap solvents (alcohol); hard; elastic and adhesive to wood and metal; takes the shape of a mould; electrical resistance.
- Uses: gramophone records and mouldings, varnishes and polishes, sealing wax, hats, emery wheels, ammunition, electrical insulation, printing inks.
6. Quick revision
- Katha = catechin; cutch = catechu-tannic acid; kheersal = white deposit. Source: khair heartwood.
- Never use iron vessels; use tinned copper. Katha separates on cooling (sparingly soluble in cold water).
- Factory yields: cutch 10 to 12%, katha 4 to 4.5%.
- Lac insect: Laccifer (Kerria) lacca. India gives 70 to 80% of world lac.
- Major hosts: palas, ber, kusum; kusum gives the best lac.
- Kusmi: Aghani, Jethwi. Rangeeni: Baisakhi, Katki; Rangeeni 80 to 90% of output.
- Kusum 4 coupes; Rangeeni 3 coupes (3 : 1 : 3). Brood stick settles 15 to 20 times its length.
7. Interactive MCQ Quiz
16 questions. Tap an option to see the answer and explanation, then go to the next question.
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