Silk Fabric Guide: Types, Properties & Sourcing Tips

Did you know that over 78% of luxury silk garments sold globally in 2023 were made from mulberry silk—but only 12% of buyers could reliably distinguish it from blended or low-grade alternatives? As a mill owner who’s spun, woven, and shipped over 42 million meters of silk across 37 countries since 2006, I’ve seen too many designers fall in love with a ‘silk’ label—only to face seam slippage at grade, catastrophic shrinkage after steam pressing, or dye migration during reactive dyeing. Let’s fix that. This isn’t a glossary. It’s your field manual for types of silks—grounded in loom tension, cocoon chemistry, and real-world performance.

Why Silk Isn’t Just One Fabric—It’s Four Distinct Species

Silk isn’t a fiber category like cotton or polyester—it’s a biological output. And just as Pinot Noir and Cabernet Sauvignon share grape DNA but express wildly different terroir, the four principal types of silks originate from different moth species, feeding regimens, and rearing environments. Their molecular structures diverge at the fibroin level—meaning tensile strength, moisture regain, dye affinity, and thermal response aren’t subtle variations. They’re material families.

Here’s the non-negotiable truth: You cannot substitute one silk for another without recalibrating your entire production chain—from digital printing pH buffers to heat-setting temperatures on air-jet looms. Let’s break them down by origin, structure, and behavior.

Mulberry Silk (Bombyx mori)

Origin: Domesticated silkworm fed exclusively on white mulberry leaves (Morus alba) under controlled climate (22–28°C, 65–75% RH)
Fiber specs: Continuous filament, 1.25–1.35 denier, 700–900 MPa tensile strength, 30% moisture regain
Weaving: Warp yarn count: Ne 20/2 to Ne 30/2; weft: Ne 18/2 to Ne 24/2; typical width: 110–140 cm; selvedge: self-finished, tightly bound
GSM range: 8–220 g/m² (e.g., chiffon = 8–12 g/m²; heavy dupioni = 180–220 g/m²)
Drape & hand feel: Liquid drape, cool-to-touch, smooth with faint crispness—like water flowing over polished river stones

Mulberry is the gold standard—not because it’s ‘purest,’ but because its uniform filament length (1,000–1,500 m per cocoon) enables high-speed rapier weaving at 220–280 picks/min without filament breakage. Its near-perfect triangular cross-section reflects light evenly—giving that signature luminous sheen. For reactive dyeing, it achieves >95% color yield with C.I. Reactive Blue 21 at pH 10.5–11.0 (per AATCC Test Method 8-2016).

Tussar Silk (Antheraea mylitta)

Origin: Wild silkworm feeding on Terminalia tomentosa and Sal leaves in forested regions of Jharkhand, Chhattisgarh, and Odisha (India)
Fiber specs: Shorter staple (100–300 m), irregular diameter (1.5–2.2 denier), lower tensile strength (450–550 MPa), higher absorbency (38% moisture regain)
Weaving: Often handloomed or low-speed air-jet; warp/weft count rarely exceeds Ne 12/2; width typically 90–110 cm; selvedge often frayed or reinforced with cotton
GSM: 110–160 g/m² (commonly used for structured jackets and artisanal shawls)
Drape & hand feel: Rustic drape, nubby texture, warm hand feel—like sun-baked clay tiles with a whisper of softness underneath

Tussar’s irregular surface scatters light, muting sheen but amplifying depth. That same irregularity makes it prone to pilling (ASTM D3443-18 rating: 2–3 on 5-point scale). It requires enzyme washing pre-dyeing to remove sericin residue—otherwise, reactive dyes bind unevenly. Colorfastness to crocking (AATCC Test Method 8) drops to Level 3–4 unless fixed with cationic aftertreatment.

Eri Silk (Samia ricini)

Origin: ‘Peace silk’—cocoons harvested post-emergence; fed on castor leaves (Ricinus communis) in Northeast India & Thailand
Fiber specs: Staple fiber (2–4 cm), no gum layer (sericin removed naturally), 1.8–2.4 denier, 320–400 MPa strength, highest moisture regain (40–45%)
Weaving: Almost always spun (not filament); yarn count Ne 10/1 to Ne 16/1; often blended with organic cotton (GOTS-certified); width: 100–120 cm
GSM: 130–190 g/m² (ideal for breathable summer suiting)
Drape & hand feel: Wool-like drape, plush, matte finish—like walking barefoot on damp moss

Eri is the outlier: it’s the only silk that’s not a filament. Its staple nature means it behaves more like wool than traditional silk—excellent insulation, zero static, and remarkable resilience to repeated washing (ISO 105-C06 wash test: retains >92% tensile strength after 5 cycles). But that also means it won’t hold sharp pleats or crisp tailoring without fusible interlinings rated for protein fibers.

Muga Silk (Antheraea assamensis)

Origin: Endemic to Assam, India; feeds exclusively on Som (Machilus bombycina) and Sopari (Persea bombycina) leaves
Fiber specs: Natural golden hue (due to xanthophyll pigments), 1.6–2.0 denier, 580–650 MPa strength, UV-resistant (UPF 35+ per AS/NZS 4399:2017)
Weaving: Traditionally handwoven on throw-shuttle looms; warp count Ne 14/2–Ne 18/2; width rarely exceeds 90 cm; selvedge often embroidered with buta motifs
GSM: 120–170 g/m² (used for heirloom saris and ceremonial wraps)
Drape & hand feel: Heavy drape, dense body, slight stiffness that softens with wear—like liquid amber poured over silk canvas

Muga’s natural gold doesn’t fade—it intensifies with age and exposure to sunlight. That’s not marketing hype; it’s photochemical stabilization of flavonoid complexes. However, its limited filament length (<200 m) makes it incompatible with modern air-jet looms above 120 picks/min. We recommend mercerization (NaOH 18%, 25°C, 30 sec) before digital printing to swell the fiber and improve ink penetration—otherwise, pigment sits on the surface and rubs off (AATCC Test Method 116: dry crock rating drops to 2).

Fabric Spotlight: Mulberry Charmeuse vs. Dupioni—Same Species, Opposite Personalities

“Dupioni isn’t ‘imperfect’ charmeuse—it’s charmeuse’s disciplined cousin who chose the artisanal path over mass production.” — Me, explaining why we keep two separate warping beams for these fabrics at our Coimbatore mill

Both derive from Bombyx mori, yet their construction defines their destiny on the runway—or the rack.

Charmeuse

Weave: Satin (5-end or 8-end) with high float length → maximizes light reflection
GSM: 12–16 g/m² (lightweight) to 28–32 g/m² (medium-weight)
Grainline: Critical—bias stretch is 12–15% (vs. 2–3% on straight grain); cutting off-grain causes torque in bias-cut gowns
Drape: Fluid, clingy, high luster—ideal for slip dresses and lingerie linings
Design tip: Use digital printing for photorealistic florals—reactive dyes penetrate uniformly due to smooth surface. Avoid enzyme washing; it dulls sheen.

Dupioni

Weave: Plain weave with slubbed yarns created by twisting two cocoons with uneven tension
GSM: 140–220 g/m²—substantial body with audible rustle
Grainline: Minimal bias stretch (<3%); stable for tailored jackets and structured skirts
Drape: Crisp, architectural, matte-sheen contrast—holds pleats for 12+ hours without steaming
Design tip: Perfect for digital foil stamping and laser-cut appliqués—its textured surface grips adhesives better than charmeuse. Pre-test seam slippage (ASTM D434): Dupioni averages 3.2 mm at 10 lbs, versus charmeuse’s 7.8 mm.

Certification Requirements: What Each Label Actually Guarantees

Don’t trust a ‘silk’ tag. Demand proof. Here’s what each certification validates—and where loopholes hide.

Certification	What It Verifies for Silk	Key Testing Standards	Limits on Blends	Validity Period
OEKO-TEX Standard 100 Class I	No harmful residues (amines, formaldehyde, heavy metals) in finished fabric	ISO 17050-1, AATCC 112, EN ISO 14382	Allows up to 30% synthetic blend if all components certified	1 year (renewal requires full retesting)
GOTS (Global Organic Textile Standard)	Organic sericulture (no synthetic pesticides), ethical labor, wastewater treatment	ISO 29465, GOTS v7.0 Annex 3	Max 10% non-organic fiber (e.g., elastic); must be GRS-certified	1 year (annual audit required)
GRS (Global Recycled Standard)	Post-consumer recycled silk content ≥50%; chain-of-custody verified	GRS v4.1, ISO 14021	Blends allowed only with GRS-certified materials	1 year (unannounced audits)
BCI (Better Cotton Initiative)	Not applicable to silk—BCI covers only cotton. Using BCI on silk is misleading and violates REACH Annex XVII	N/A	Prohibited for silk labeling	N/A

Red flag: Any supplier claiming ‘BCI-certified silk’ is either misinformed or deliberately conflating standards. BCI has zero scope for sericulture. Similarly, ‘organic silk’ without GOTS or OCS (Organic Content Standard) certification is unverifiable—and likely refers only to mulberry leaves, not processing.

Practical Sourcing & Design Guidance

Now that you know the biology, let’s talk logistics—the part that keeps mills awake and designers frustrated.

When to Choose Which Silk Type

Mulberry charmeuse: When you need high-gloss, fluid drape, and reactive dye precision—but only if your factory has steam calendering capability. Without it, seam puckering will haunt your fit models.
Tussar: For artisanal storytelling and tactile differentiation—but budget +25% for hand-loom labor and +18% for dye lot variation allowances.
Eri: For sustainable activewear hybrids (e.g., Eri/cotton jersey) or humid-climate suiting—never for high-stretch applications (poor recovery: <15% elongation at break).
Muga: For cultural authenticity and longevity—only when your client accepts 8–12 week lead times and minimums ≥300 meters per shade.

Installation & Care Protocols

Cutting: Always cut mulberry silk with rotary blades (not shear blades)—filament damage from nicks causes run-prone edges. Grainline must be verified with a 1m plumb line before laying patterns.
Sewing: Use size 60/8 microtex needles, polyester-core silk thread (Tex 25–30), and stitch length 2.2–2.5 mm. Reduce presser foot pressure by 30% to avoid crushing the nap.
Washing: Eri and tussar tolerate gentle machine wash (30°C, wool cycle); mulberry and muga require dry clean only (PERC-free solvents preferred per REACH Annex XVII).
Steaming: Never direct-steam mulberry charmeuse—use a 15 cm standoff with vacuum suction. Muga responds best to Japanese-style kairo (dry heat ironing at 135°C).

Color Development Reality Check

Silk’s amino acid profile makes it the most reactive natural fiber to dyes—but that cuts both ways. Reactive dyes bond covalently with lysine residues, yielding exceptional wash-fastness (ISO 105-C06: Grade 4–5). However, pH shifts >0.3 during exhaust dyeing cause dramatic hue shifts—especially in violet and teal ranges. Our lab rule: always dye mulberry silk at pH 10.7 ± 0.1, monitored every 90 seconds. Tussar? pH 9.2–9.5. Eri? pH 8.5–8.8. Muga? pH 10.0–10.3. One buffer error can cost $18,000 in rejected yardage.