| Term | Meaning / Language | Significance |
|---|---|---|
| Eri | Assamese word era = castor | Silkworm feeds on castor leaves |
| Endi / Errandi | Regional variants (Assamese/Hindi) | Used interchangeably; MCQ trap |
| Indi | Bodo community name | Cultural significance to Bodo tribe |
| Ryndia | Khasi name in Meghalaya | From Rynda = castor in Khasi |
| Ahimsa Silk | Sanskrit — non-violence | Moth exits cocoon naturally; cruelty-free |
| Peace Silk | Global/commercial name | Used in international sustainable fashion |
| Poor Man's Silk | Traditional description | Coarser than mulberry; accessible to rural weavers |
| Parameter | Detail |
|---|---|
| Scientific Name | Samia cynthia ricini / Philosamia ricini |
| Family | Saturniidae (wild silkmoth family) |
| Order | Lepidoptera |
| Primary Food Plant | Castor plant (Ricinus communis) |
| Alternate Food Plants | Kesseru (Heteropanax fragrans), tapioca, papaya, Ailanthus |
| Rearing Cycle | ~30 days indoors on trays/baskets |
| Cocoon Type | Open-ended (moth exits naturally — key fact) |
| Domestication Status | Only domesticated non-mulberry silk in India |
Eri is the only commercially produced vegan silk in the world — the Samia ricini moth naturally exits through an open end of the cocoon, so the cocoon is never boiled to kill the pupa (unlike mulberry, tasar, and muga silk processes).
| Silk Type | Silkworm | Food Plant | Special Feature | Key State |
|---|---|---|---|---|
| Mulberry | Bombyx mori | Mulberry | Largest share (~71%); reelable filament | Karnataka |
| Eri | Samia ricini | Castor | Only vegan silk; spun not reeled | Assam |
| Tasar (Tussar) | Antheraea mylitta | Arjun/Asan trees | Wild silk; tribal communities; natural tan | Jharkhand/Odisha |
| Muga | Antheraea assama | Som/Sualu plants | Golden hue; exclusive to Assam; most expensive | Assam only |
India is the only country in the world producing all four commercial silks — Mulberry, Eri, Tasar, and Muga. This is a classic UPSC Prelims statement. Also note: Muga is exclusive to India (specifically Assam), while Eri is found in India, China, Japan, and Thailand.
Eri silk cultivation traces its roots to the Brahmaputra valley of Northeast India, with a history spanning over 2,000 years. The silkworm, Samia cynthia ricini, is believed to have originated in the Brahmaputra valley and historically had restricted distribution in India, China, and Japan. Unlike mulberry sericulture (which originated in China around 2700 BC), Eri culture emerged as an indigenous tradition of Northeast India's tribal communities — particularly among the Bodo, Mishing, Khasi, and Karbi communities of Assam and Meghalaya.
The skill of extracting Eri silk fibres and weaving has been practised for generations as a female occupation — rural and tribal women in Assam processed, spun, and wove Eri silk as part of daily life. It is described as the "father of all forms of cultured and textured silks."
India produces over 90% of the world's Eri silk. Even as Thailand introduced Eri silkworms (1974) and China/Japan have small-scale production, India — especially Assam — remains the overwhelmingly dominant producer and cultural origin of Eri silk globally.
| Property | Detail | Exam Relevance |
|---|---|---|
| Fibre Type | Spun (not reeled) — open-ended cocoon breaks filament continuity | MCQ on process difference vs mulberry |
| Texture | Coarse, dense, fine — described as woolly | Called "poor man's silk"; heavier than mulberry |
| Warmth | Good insulator; suitable for winter use | All-weather silk; used in shawls |
| Durability | Strong and elastic; shorter fibres than mulberry | Heavier and more durable than mulberry silk |
| Colour (natural) | White to faintly gold / dull yellow | Rust-red variant from Kokrajhar (Assam) is notable |
| Hypoallergenic | Yes — no harmful chemicals in natural production | Supports Oeko-Tex certification rationale |
| Anti-fungal | Natural anti-fungal properties | Adds to textile value proposition |
| Breathability | Breathable and moisture-absorbent | NEHHDC markets for baby products, wellness |
| Chemical-free | No chemicals in rearing or cocoon processing | Core basis of Oeko-Tex certification |
| Colour | Source / Feed | Region |
|---|---|---|
| White Eri | Standard castor leaf diet | Dominant across Northeast India |
| Red/Rust-red Eri | Worms additionally fed on Ficus tree leaves | Kokrajhar district, Assam — notable variant |
| Gold-tinted | Natural silkworm pigmentation | Gives dull yellow/gold-like sheen |
Eri silk cannot be reeled — because the cocoon is open-ended, the silk filament is broken. It must be hand-spun (on a drop spindle or motorized single spindle), which gives it its distinctive spun-yarn texture.
Endi shawls from Assam are traditionally offered as gifts of honour in Bihar and Nepal — a cultural connection often tested in Prelims.
| State | Share of India's Eri Production | Notes |
|---|---|---|
| Assam | 38.3% | Dominant producer; heartland of Eri culture; Bodo, Mishing communities |
| Manipur | 29.8% | Second largest; significant tribal production |
| Meghalaya | 22.6% | Khasi communities; Ryndia silk; Ri-Bhoi district |
| Nagaland | 6.8% | Smaller scale; tribal tradition |
| Others | ~2.5% | Arunachal Pradesh, Bihar, West Bengal, Odisha, Andhra Pradesh (minor) |
Northeast India is the only region in India producing four varieties of silk simultaneously — Mulberry, Oak Tasar, Muga, and Eri. Overall, NE region contributes about 18% of India's total silk production.
| Silk Type | Production (MT) | Share (%) | Dominant State |
|---|---|---|---|
| Mulberry | 25,213 | 71.5% | Karnataka (32%+ of national) |
| Eri | 6,839 | 19.4% | Assam (38.3% of Eri) |
| Tasar | 2,977 | 8.4% | Jharkhand, Chhattisgarh, Odisha |
| Muga | 232 | 0.66% | Assam (94.6% of Muga) |
| Parameter | Detail |
|---|---|
| India's global rank | 2nd largest producer (after China) |
| India's global production share | ~42% of global silk (2023 estimate); ~13% of raw silk historically |
| China + India combined | Over 90% of world silk production |
| Global silk market value | ~USD 16 billion |
| India's silk exports | To 90+ countries; ~USD 360 million |
| India's unique distinction | Only country producing ALL four commercial silk varieties |
| Karnataka's distinction | Silk Capital of India; largest silk-producing state (mulberry) |
| Muga's distinction | Exclusive to India (Assam); most expensive; golden colour |
Eri silk prices: approximately ₹2,900/kg (spun yarn, 2021-22) — cheaper than mulberry (₹3,421/kg) and far cheaper than Muga (₹19,800/kg). Muga is the most expensive Indian silk. This is a data point that could appear in UPSC MCQs on sericulture economics.
| Parameter | Detail |
|---|---|
| Full form | Oeko-Tex Association (International Association for Research and Testing in the Field of Textile and Leather Ecology) |
| Founded | 1992 — by an Austrian Textile Research Institute |
| Headquarters | Germany (globally administered) |
| Nature | Independent, third-party certification for textile safety and sustainability |
| Scope | Yarns, fabrics, buttons, linens, terry cloth, threads, and all accessory materials |
| Standard Updated | Annually (criteria updated to reflect latest scientific and regulatory findings) |
| Certified Companies | Over 35,000 companies worldwide |
| Tests Against | Over 1,000 chemical substances |
| Standard | What It Certifies | Key Feature |
|---|---|---|
| STANDARD 100 | Finished textile products — free from harmful substances | Most common; consumer-facing label; tests every component including threads, buttons |
| MADE IN GREEN | Textiles tested for harmful substances AND produced sustainably & socially responsibly | Combined safety + sustainability label |
| STeP (Sustainable Textile Production) | Sustainability of production sites/factories | Company-level, not product-level |
| ECO PASSPORT | Chemical inputs used in textile production | For dyes, finishing agents |
| LEATHER STANDARD | Leather articles tested for harmful substances | Non-textile; leather-specific |
| ORGANIC COTTON | Organic cotton from farm to product; GMO-free | Farm-level verification |
| Class | Product Type | Strictness |
|---|---|---|
| Class I | Products for babies & children under 3 (bodysuits, bibs, sleepsuits) | Most strict — infant skin most vulnerable |
| Class II | Direct skin contact (underwear, T-shirts, socks) | Stringent chemical limits |
| Class III | No direct skin contact (outer garments, curtains) | Moderate limits |
| Class IV | Decoration materials (furniture, carpets) | Least strict |
| Dimension | What It Means |
|---|---|
| Market Access | Allows Indian Eri silk exporters to enter high-end European, American, Japanese markets that mandate eco-safety certification |
| Consumer Confidence | Assures international buyers Eri silk is free from over 1,000 harmful substances; safe for all uses including baby products |
| Compliance | Meets REACH (EU chemical regulation), CPSIA (US), and ECHA-SVHC standards — legally required in many export markets |
| Competitive Edge | Positions Eri as credible alternative to synthetic eco-fabrics and other "sustainable" textiles in global market |
| Sustainability Alignment | Aligns with global sustainable fashion trends; appeals to vegan, cruelty-free, ethically conscious consumers |
| Unorganized Sector | Despite certification, Eri weaving remains largely unorganized — certification is a bridge to organized global trade |
Oeko-Tex STANDARD 100 tests every component of a textile product — not just the main fabric, but also threads, buttons, zippers, linings, and accessories. This comprehensive testing is why the certification is internationally recognized as the gold standard of textile safety.
The UPSC-relevant linkage: Oeko-Tex = German-origin international textile certification + NEHHDC = body under Ministry of DoNER + Eri silk = Art & Culture (Northeast) + sustainability narrative. This topic sits at the intersection of Art & Culture, Environment, and Economy — expect statement-type questions about which body received the certification and which ministry it falls under.
| Institution / Body | Est. Year | Ministry / Parent | Role in Eri Silk |
|---|---|---|---|
| Central Silk Board (CSB) | 1948 | Ministry of Textiles | Apex statutory body for all sericulture; R&D, training, quality, exports |
| CMER&TI (Central Muga Eri Research & Training Institute) | 1999 (est. as station 1972) | CSB / Ministry of Textiles | Apex R&D for Muga & Eri; located at Lahdoigarh, Jorhat, Assam |
| NEHHDC (North Eastern Handicrafts & Handlooms Development Corp.) | — | Ministry of DoNER | Received Oeko-Tex certification for Eri silk (Aug 2024); promotes NE handicrafts & handlooms |
| Muga Eri Silkworm Seed Organization | — | CSB / Ministry of Textiles | Maintenance, production & supply of quality Eri silkworm seeds (DFLs — Disease Free Layings) |
| ISEPC (Indian Silk Export Promotion Council) | — | Ministry of Textiles | Apex export promotion body; explores international markets for all silk including Eri |
| Directorate of Sericulture, Assam | — | Govt. of Assam | Maintains state network of Muga, Eri seed farms; supplies quality DFLs to farmers |
| Scheme | Period / Budget | Ministry | Relevance to Eri |
|---|---|---|---|
| Silk Samagra-2 | 2021-22 to 2025-26 / ₹4,679.85 crore | Ministry of Textiles | Covers Eri silk; promotes advanced tech, sustainable practices, quality certification, export branding |
| NE Region Textile Promotion Scheme | Ongoing | Ministry of Textiles | Special focus on revival & diversification of Eri and Muga in Northeast India |
| PM MITRA (Mega Integrated Textile Region & Apparel Parks) | 2021 onwards | Ministry of Textiles | Broad textile infrastructure; indirectly supports silk processing units |
| Silk Samagra (original) | 2017-20 | Ministry of Textiles | Predecessor scheme; quality improvement, R&D, market development |
Silk Samagra-2 budget: ₹4,679.85 crore for 2021-22 to 2025-26. Key components: R&D, training, technology transfer, quality certification systems (QCS), export brand promotion, and technology up-gradation. This is UPSC Prelims-relevant data.
CMERTI location: Lahdoigarh, Jorhat, Assam. It has nested units including Regional Sericultural Research Stations (RSRS) at Boko (Assam) and Imphal (Manipur), and a network of three Regional Extension Centres (RECs).
The Oeko-Tex certification was received by NEHHDC (under Ministry of DoNER) — NOT by the Central Silk Board or Ministry of Textiles directly. This distinction is a classic UPSC trap: students assume CSB/Ministry of Textiles received it. NEHHDC is the correct answer.
| Community | State | Eri Connection | Key Cultural Product |
|---|---|---|---|
| Bodo (Boro-Kachari) | Assam | Earliest settlers of Brahmaputra valley; Eri (called "Indi") is integral; women weave on looms in households | Dokhona, Jomgrah, Aronai — all GI-tagged |
| Mishing | Assam / Arunachal | Migrated from Arunachal; women weave with Eri; known for weaving in 7 colours simultaneously | Ghai-yamik motifs; GI-tagged Mising products |
| Khasi | Meghalaya | Call Eri silk "Ryndia"; exclusively woven by women in Ri-Bhoi district; intergenerational skill | Traditional Khasi Ryndia shawls |
| Karbi / Khadar Lyngdoh | Meghalaya / Assam | Interethnic Eri weaving communities in Ri-Bhoi district; cultural assimilation through motifs | Shared Ri-Bhoi district weaving identity |
| Monpa | Arunachal Pradesh | Use Eri silk in traditional garments; part of regional silk culture | Traditional Monpa textiles |
In Assam, textile weaving — including Eri silk — has historically been an exclusively female occupation. Over 80% of Assam's weavers are women, making handloom weaving a major driver of rural women's economic empowerment.
| Product | GI Tag Region | Significance |
|---|---|---|
| Bodo Eri Silk | Assam (Bodo community) | Directly GI-tagged; protects Bodo cultural heritage; prevents imitations |
| Muga Silk | Assam | Golden-hued silk; exclusive to Assam; GI-tagged |
| Dokhona | Assam (Bodo) | Bodo women's draped skirt, often made with Eri silk; GI-tagged |
| Jwmgra | Assam (Bodo) | Patterned narrow cloth; GI-tagged |
| Aronai | Assam (Bodo) | Bodo men's upper cloth; GI-tagged |
| Bodo Gamusa | Assam (Bodo) | Traditional towel/cloth; GI-tagged |
| Mising Handloom Products | Assam (Mishing) | GI-tagged; includes Eri-based weaves |
| Assamese Gamusa | Assam | Iconic identity cloth; GI-tagged |
| Faith / Philosophy | Connection to Eri Silk |
|---|---|
| Jainism | Strict non-violence principle (Ahimsa) makes Eri the only acceptable silk; Jains prefer it as no creature is killed |
| Buddhism | Buddhist monks across India, Bhutan, Nepal, China, Japan have historically preferred Eri silk for centuries |
| Vegan/Ahimsa Movement | Global vegan fashion movement positions Eri as the only acceptable natural silk; growing European/American demand |
| Gandhian Philosophy | Cottage industry, women empowerment, non-violence — Eri aligns perfectly with Swadeshi and Ahimsa ideals |
In the Khasi tradition of Meghalaya, an Eri silk shawl or baby sling is passed down for generations as a family heirloom — testament to the fabric's durability and deep cultural significance. In Bihar and Nepal, Endi shawls are given as gifts of honour.
The Handloom (Products Preservation) Act, 1985 protects 11 traditional fabrics including Gamusa and Mekhela-Chador — these can only be produced on handlooms. Eri silk weaving is also traditionally handloom-based, making it relevant to this Act's protective framework.
| Country | Role / Status | Key Data |
|---|---|---|
| India | Origin & dominant producer; largest Eri producer | >90% of world's Eri silk; 7,000+ MT (FY23); Oeko-Tex certified (2024) |
| China | Has small-scale Eri production; primarily mulberry silk dominant | World's #1 silk producer overall; far smaller Eri share than India |
| Japan | Historical Eri production; known for refining and dyeing techniques | Minor Eri producer; known for finishing precision |
| Thailand | Introduced Eri in 1974 (imported from India) | Growing Eri production using cassava leaves; Queen Sirikit Sericulture Center active |
| Bhutan / Nepal | Traditional consumers, not major producers | Buddhist communities historically favour Eri as Ahimsa silk |
| Certification | Focus | Issuing Body | Eri Silk Link |
|---|---|---|---|
| Oeko-Tex STANDARD 100 | Textile safety — free from harmful substances | Oeko-Tex Association, Germany | Received by NEHHDC for Eri silk (2024) |
| GOTS (Global Organic Textile Standard) | Organic fibre + environmental + social standards | GOTS Association | Possible future certification angle for Eri |
| BCI (Better Cotton Initiative) | Sustainable cotton farming | BCI Association | Not directly applicable to silk |
| bluesign | Responsible manufacturing for synthetic textiles | bluesign technologies | Not directly applicable to silk |
| GI Tag (India) | Geographical origin protection | Ministry of Commerce, India | Bodo Eri Silk, Muga Silk — GI-tagged |
The global sustainable textile market is growing rapidly. Eco-conscious consumers in North America and Europe increasingly demand ethically produced, animal-friendly textiles. This shift is boosting Eri silk's popularity. NEHHDC's Eri Silk Spinning Plant in Baksa, Assam now offers international buyers export-ready, traceable, quality-tested Eri yarn — with markets in Europe, Japan, US, and Southeast Asia.
The European Union's REACH regulation (Registration, Evaluation, Authorisation and Restriction of Chemicals) restricts harmful substances in textiles sold in the EU. Oeko-Tex STANDARD 100 specifically ensures compliance with REACH's Annexes XVII and XIV, plus the CPSIA (US Consumer Product Safety Improvement Act) and ECHA-SVHC (European Chemicals Agency — Substances of Very High Concern) candidate list. This means Eri silk with Oeko-Tex certification is legally cleared for sale in the world's most regulated textile markets — Europe and the US.
NEHHDC receives Oeko-Tex Certification for Eri Silk: The North Eastern Handicrafts and Handlooms Development Corporation (NEHHDC) under the Ministry of Development of North Eastern Region (DoNER) received the Oeko-Tex certification directly from Germany for its Eri silk. The announcement was made on India's 78th Independence Day (August 15, 2024). The certification was awarded by the Oeko-Tex Association, headquartered in Germany, confirming Eri silk is free from harmful substances and produced under environmentally friendly conditions.
Parliamentary Confirmation: Minister of State for the Ministry of Development of North Eastern Region, Dr. Sukanta Majumdar, in a written reply to the Rajya Sabha stated that NEHHDC has received the Oeko-Tex certification from Germany for Eri silk. He noted the certification "enhances the credibility of eri silk and strengthens its position in the international market by assuring buyers of its compliance with global safety and quality standards." This makes it Rajya Sabha-documented — extremely relevant for UPSC.
Silk Samagra-2 Scheme in Final Phase: The scheme (budget ₹4,679.85 crore) covering 2021-22 to 2025-26 is in its final year. It specifically promotes Eri silk through advanced technology adoption, quality certification (such as Oeko-Tex), sustainable practices, and export brand promotion. CMERTI continues R&D under this scheme to increase Eri silk productivity and modernize post-cocoon processing.
India's Silk Production Dips: The Central Silk Board projected India's total raw silk production at 30,614 tonnes for 2024-25 (April–December data) — a notable fall from FY24's 38,913 MT. This is the first decline in four years, largely driven by pest outbreaks in Karnataka (mulberry silk). Eri silk's Northeast-based production is relatively insulated from this trend. (Source: Central Silk Board / Deccan Herald, 2024-25)
Eri Silk Champion Awarded Padma Shri: Jogesh Deuri, a sericulturist and researcher from Goalpara district, Assam, known for his significant contributions to the development and promotion of Eri and Muga silk in Northeast India, was awarded the Padma Shri in 2026 (fourth-highest civilian honour) for contributions to agriculture and sericulture. He received the Assam Gaurav award in 2023. (Source: Wikipedia / PTI, 2026)
The Oeko-Tex certification for Eri silk is one of the most UPSC-relevant Art & Culture + Environment + Economy crossover topics of 2024-25. Expect questions on: (1) Which body received Oeko-Tex? (2) Under which Ministry is NEHHDC? (3) What does Oeko-Tex certify? (4) Where is Eri silk primarily produced? (5) What is Eri silk's other name? All five are standard Prelims MCQ territory.
| # | Statement | Verdict | Correct Understanding |
|---|---|---|---|
| 1 | "Eri silk is produced from wild silkworms that feed on arjun and asan trees." | ❌ False | Eri is produced from Samia ricini feeding on castor leaves. It is the Tasar (Tussar) silk that uses arjun/asan trees. |
| 2 | "Eri silk is the only silk variety exclusive to India." | ❌ False | Muga silk is exclusive to India (Assam only). Eri silk is also found in China, Japan, and Thailand. |
| 3 | "Oeko-Tex certification for Eri silk was received by the Central Silk Board under Ministry of Textiles." | ❌ False | It was received by NEHHDC under the Ministry of DoNER — not CSB/Ministry of Textiles. |
| 4 | "Eri silk is obtained by reeling continuous filaments from boiled cocoons." | ❌ False | Eri silk is spun not reeled. The open-ended cocoon cannot be reeled; the moth exits naturally and the cocoon is then spun into yarn. |
| 5 | "Muga silk and Eri silk are both produced in Assam." | ✅ True | Both Muga (exclusively Assam) and Eri (Assam is largest producer at 38.3%) are produced in Assam. NE India produces all four silk types. |
| 6 | "Bodo Eri Silk has received a Geographical Indication (GI) tag." | ✅ True | Bodo Eri Silk has a GI tag; five traditional Bodo textiles have GI tags — Dokhna, Bodo Eri Silk, Bodo Gamusa, Jwmgra, Aronai. |
| 7 | "Eri silk is called 'Ahimsa silk' because no silkworm is used in its production." | ❌ False | Silkworms ARE used — but the moth is not killed. It exits naturally from the open-ended cocoon. Ahimsa = non-violence in the production process, not absence of silkworms. |
| 8 | "India is the only country that produces all four major commercial silks." | ✅ True | India produces Mulberry, Eri, Tasar, and Muga — all four. This is a definitive India-unique distinction. |
Students mix up Eri (castor-fed, Samia ricini, Assam) with Tasar (arjun/asan tree-fed, Antheraea mylitta, Jharkhand/Odisha). UPSC often gives a feature of one and asks which silk it describes. Eri = castor = Assam = open cocoon = vegan. Tasar = forest trees = Central India = tribal communities.
Both Muga and Eri can have a slightly golden/yellowish tint — but Muga is the true "golden silk" of Assam with its distinctive natural golden glitter. Eri has a dull yellow/gold-like sheen. If UPSC asks "which silk is known for its golden hue and is exclusive to India?" — the answer is Muga, not Eri.
NEHHDC (Ministry of DoNER) received the Oeko-Tex certification — NOT the Central Silk Board (Ministry of Textiles). Students who know CSB as the main silk body assume CSB got the cert. NEHHDC is the key answer.
Eri is called "the only domesticated silkworm native to India." This means it is reared indoors, on trays, unlike Muga and Tasar which involve wild/forest-based rearing. Mulberry silk (Bombyx mori) is also domesticated — but not native to India (it originated in China). So Eri = only domesticated non-mulberry silk that is native to India.
Karnataka is India's largest silk-producing state overall — but for mulberry silk only. Karnataka does NOT significantly produce Eri silk. Eri's dominant state is Assam (38.3%). Students confuse "silk capital" (Karnataka) with "Eri silk capital" (Assam).
UPSC has previously asked about Gucchi mushroom (Himalayan, not cultivated — 2022), Muga silk, and GI-tagged products from Northeast India. Eri silk + Oeko-Tex is a high-probability Prelims 2026 topic given its August 2024 PIB origin and Rajya Sabha reference in March 2025. Statement-type questions and pair-matching are the likely formats.
| Feature | Eri | Mulberry | Tasar | Muga |
|---|---|---|---|---|
| Silkworm | Samia ricini | Bombyx mori | Antheraea mylitta | Antheraea assama |
| Food Plant | Castor | Mulberry | Arjun / Asan | Som / Sualu |
| Key State | Assam | Karnataka | Jharkhand | Assam (exclusive) |
| Cocoon | Open-ended | Closed | Closed (wild) | Closed (wild/semi) |
| Process | Spun | Reeled | Reeled/spun | Reeled |
| Ahimsa? | Yes (only one) | No | No | No |
| Global Exclusivity | No (also China, Japan, Thailand) | No | No | Yes — India only |
| Price (2021-22) | ₹2,900/kg | ₹3,421/kg | Lower | ₹19,800/kg |
For UPSC Prelims 2026: The single most important fact from this topic — Eri silk received Oeko-Tex certification in August 2024 through NEHHDC under Ministry of DoNER (not CSB/Ministry of Textiles). Pair this with: silkworm = Samia ricini, food = castor, process = spun not reeled, location = Assam (38.3%), and the term Ahimsa silk.