What Standard Governs Silk Quilt Testing in China?
Silk quilt testing in China is governed by GB/T 24252-2019 Silk Quilts, which replaced the 2009 edition and took effect on May 1, 2020. The scope covers quilts filled with mulberry silk (桑蚕丝) or tussah silk (柞蚕丝), or a blend of both, as the main wadding material — set inside a wadding cover and fixed by machine stitching or hand quilting. Any quilt sold as a "silk quilt" in the domestic market must have ≥ 50 % silk content in the fill; only a quilt with 100 % silk fill may be labelled "pure silk quilt" (纯蚕丝被).
Two safety standards sit on top of the product standard. Every silk quilt must comply with GB 18401-2010 National General Safety Technical Code for Textile Products — the mandatory baseline for all textiles sold in China. Infant and children's silk quilts must additionally comply with GB 31701 Safety Technical Code for Textile Products for Infants and Children. Knowing this three-standard stack up front determines the full scope of a test plan: the product standard covers quality, while the safety standards cover what the consumer actually breathes and touches.
What Are the Safety Performance Requirements?
Safety performance under GB/T 24252 routes through GB 18401, which classifies textiles into three categories with hard thresholds. A silk quilt, worn next to the skin in bed, almost always falls under Category B (direct contact with skin); an infant silk quilt falls under Category A.
| Parameter | Category A (infant) | Category B (direct contact) | Category C (non-contact) |
|---|---|---|---|
| Formaldehyde | ≤ 20 mg/kg | ≤ 75 mg/kg | ≤ 300 mg/kg |
| pH value | 4.0 – 7.5 | 4.0 – 8.5 | 4.0 – 9.0 |
| Decomposable carcinogenic aromatic amines | ≤ 20 mg/kg (24 banned azo dyes) | same | same |
| Odour | none allowed | none allowed | none allowed |
GB/T 24252-2019 also narrows the pH requirement for the silk fill itself to 4 – 8, tighter than the GB 18401 Category B band, because silk protein fibre is sensitive to alkaline hydrolysis — a fill that drifts alkaline will yellow and embrittle over time. This is one of the changes introduced in the 2019 revision: the pH limit applies to the silk wadding, not just the outer cover.
The no broken needles rule is a separate safety requirement: the quilt must contain no sewing needles, broken needles, or any other metal pieces that could cause injury. This is verified by a metal-detection step in delivery inspection, and a positive finding is an automatic fail regardless of every other result.
How Is the Silk Fill Itself Evaluated?
The internal-quality block is where GB/T 24252-2019 concentrated its 2019 revisions. The fill (蚕丝绵, silk floss) is graded into 优等品 (premium), 一等品 (first grade), 合格品 (qualified) tiers, and the thresholds that separate them are quantified:
Oil content (含油率): the residual sericin-processing oil in the silk floss. Premium and first-grade quilts must stay ≤ 1.5 %; qualified grade ≤ 1.8 %. High oil content is the tell-tale of an under-processed or over-softened fill — it leaves a greasy hand feel, accelerates oxidation, and is the most common reason a premium-claimed quilt tests down to qualified.
Residual gum content (残胶率): a new item introduced in the 2019 revision. Premium grade requires ≤ 5.0 %. Too much residual sericin makes the floss stiff and prone to caking; too little means the fibre has been over-degummed and loses strength. The 5 % ceiling is the premium-tier discriminator.
Fluorescent whitening agents (荧光增白剂): non-detectable in the fill. This is the item that catches manufacturers who bleach and brighten inferior or recycled silk to mimic the pearl lustre of high-grade mulberry silk. The test uses UV inspection — any fluorescence in the fill fails, because genuine silk floss is naturally milky white with no optical brightener.
Moisture regain (回潮率): the equilibrium moisture of the silk, which affects weight and feel. GB/T 24252 sets a controlled range; a fill weighed at artificially high moisture is one of the weight-inflation frauds the standard was revised to catch.
Mass deviation rate (质量偏差率): the measured fill weight against the labelled weight. The 2019 revision tightened this — a quilt labelled "1.5 kg silk" cannot come in materially under, and the standard explicitly bans any weight-adding process (增重处理) on the silk wadding. This single clause kills the older fraud of treating silk with hygroscopic salts to inflate weigh-in readings.
Compressibility and recovery (压缩回弹性): measured per Annex B of the 2019 standard — the fill is compressed under a defined load, then released, and its thickness recovery is recorded. Good recovery is what keeps the quilt lofty and warm after years of use; a fill that collapses under load and stays flat is short-staple or mechanically damaged silk.
How Is Fibre Content Verified and Why Does It Matter?
Fibre content is the single most litigated result in a silk quilt report, because it is where fraud actually happens. GB/T 24252 requires the wadding cover and the fill to be tested separately, and the result must be reported against the label per GB/T 29862 Textiles — Designation of Fibre Content.
The fraud patterns the test must catch:
- Short silk passed off as long silk. Long-staple mulberry silk (a single floss that can be hand-pulled to 10+ metres without breaking) is the premium fill; short silk (碎绵, chopped or reclaimed) is cheaper, pills, and cakes. The 2019 revision added a silk floss length (丝绵长度) requirement precisely to grade this, and deleted the old "long / medium-long / short" terminology in favour of a measured length value.
- Tussah passed off as mulberry. Tussah (柞蚕) silk is naturally greyish-brown and is acid-bleached to mimic mulberry's milky white; the price gap is roughly 3–4×. Microscopic fibre identification (longitudinal scale structure) and the burn test separate them.
- Cotton, polyester, or kapok blend passed off as pure silk. The qualitative test is the 84-disinfectant (sodium hypochlorite) dissolution method — silk dissolves in domestic bleach within minutes; cotton and polyester do not. This is the consumer-grade version; the laboratory-grade version uses the GB/T 2910 quantitative chemical analysis family.
- Weight inflated with wet treatment or added chemicals. Caught by the mass-deviation-rate and no-weight-adding clauses.
A fibre-content report that only states "100 % silk" without specifying the test method (microscopy + chemical dissolution) is not defensible. The complete report gives the measured composition by mass, the method standard, and the deviation from label.
What Are the Colorfastness and Dimensional Stability Requirements?
The wadding cover (胎套) is tested for colourfastness because it is the layer the consumer's skin touches and the layer that is washed. GB/T 24252 requires:
- Colourfastness to washing (with soap, or soap and soda)
- Colourfastness to perspiration (acid and alkaline)
- Colourfastness to water
- Colourfastness to dry rubbing
Premium and first grades demand ≥ 3–4 grade; qualified grade ≥ 3 grade. A cover that bleeds dye into the silk fill on the first wash ruins the quilt — the colourfastness test is what prevents that.
Dimensional change after washing (水洗尺寸变化率): the cover's shrinkage. The 2019 revision revised the test method; a cover that shrinks more than the allowed percentage will pucker and pull the silk fill out of position, creating cold spots. This is measured on the cover fabric before quilting and on the finished quilt after a defined wash cycle.
How Do You Detect Counterfeit Silk — Laboratory Methods vs. Burn Test?
The consumer-facing burn test (silk burns to crushable ash with a hair-burning smell; polyester melts to a hard bead with a plastic smell) is a useful screen, but it has a hard limit: it cannot distinguish mulberry from tussah, and it cannot quantify a blend. A quilt labelled "100 % mulberry silk" that is actually 60 % tussah + 40 % polyester will pass a burn test — all three are fibres that burn — but will fail a laboratory fibre-content analysis.
The laboratory-grade test stack for a fraud-confirmation report:
- Microscopic examination (FZ/T 01057.3) — longitudinal and cross-section morphology. Mulberry and tussah have different scale patterns; cotton, polyester, and kapok are unmistakable.
- Chemical quantitative analysis (GB/T 2910 series) — selective dissolution. Silk dissolves in sodium hypochlorite or formic acid/zinc chloride; the residue is weighed to give the non-silk percentage.
- Burn test (FZ/T 01057.2) — confirms protein fibre vs. synthetic, used as a cross-check, not the primary method.
- UV inspection for fluorescent whitening agents — catches bleached-and-brightened inferior silk.
- Residual gum and oil content — a fill with high residual gum and high oil is almost always under-processed reclaimed silk, not first-run mulberry.
The pattern: a consumer can screen with burn + bleach + touch, but a report that holds up in a contract dispute or a market-supervision review needs the chemical and microscopic methods. The burn test alone is not evidence.
Our Testing Capabilities
Beijing ZKGX Research provides silk quilt testing against the GB/T 24252-2019 product standard and the GB 18401 / GB 31701 safety framework.
Safety performance (GB 18401 / GB 31701):
- Formaldehyde (Category A/B/C thresholds)
- pH value (4–8 for silk fill; GB 18401 band for cover)
- Decomposable carcinogenic aromatic amines (24 banned azo dyes)
- Colourfastness to washing, perspiration, water, rubbing
- Odour, broken-needle metal detection
Internal quality of silk fill (GB/T 24252-2019):
- Fibre content by chemical dissolution + microscopy (GB/T 2910, FZ/T 01057)
- Oil content (premium/first ≤ 1.5 %; qualified ≤ 1.8 %)
- Residual gum content (premium ≤ 5.0 %)
- Fluorescent whitening agents (non-detectable, UV inspection)
- Silk floss length, moisture regain, mass deviation rate
- Compressibility and recovery (Annex B)
Finished-quilt quality: cover colourfastness, dimensional change after washing, appearance and process quality, label vs. measured fibre content (per GB/T 29862).
If you need a GB/T 24252 silk quilt report — for e-commerce platform entry, market-supervision response, or a supplier quality dispute where the burn test is not enough — contact our laboratory with the quilt's labelled fibre content, labelled fill weight, and target grade, and we will scope the test plan.
FAQ
What is the difference between a silk quilt and a pure silk quilt?
Under GB/T 24252, a quilt may be labelled "silk quilt" (蚕丝被) if its fill is ≥ 50 % silk. Only a quilt with 100 % silk fill may be labelled "pure silk quilt" (纯蚕丝被). A quilt between 50 % and 100 % is a "blended silk quilt" (混合蚕丝被). The fibre-content test determines which label is legal — and a quilt labelled "pure silk" that tests at 70 % is mislabelled, regardless of how it feels or burns.
Why does GB/T 24252 cap oil content at 1.5 %?
The oil is residual processing oil left on the silk floss after degumming and opening. Above 1.5 %, the floss feels greasy, oxidises faster (yellowing and embrittlement), and attracts dust. The 1.5 % / 1.8 % split between premium and qualified grades is the discriminator that forces manufacturers who claim premium to actually finish their silk properly, not just label it premium.
Can the burn test prove a silk quilt is genuine mulberry silk?
No. The burn test confirms a fibre is protein-based (silk, wool, hair) vs. synthetic (polyester, nylon) — it cannot tell mulberry from tussah, and it cannot quantify a blend. A quilt that is 60 % tussah + 40 % polyester will burn like silk on the 60 % and like plastic on the 40 %, and a consumer doing a single burn will often read it as "silk." For a defensible result you need microscopic identification plus chemical dissolution (GB/T 2910).
What does "no weight-adding process" mean in the 2019 revision?
The 2019 revision explicitly bans treating the silk fill with hygroscopic chemicals (salts, sugars) or excessive wet processing to inflate its weigh-in mass. The fraud worked like this: a quilt labelled 1.5 kg might contain 1.3 kg of silk treated to absorb 200 g of moisture or salt at the weigh-in, then lose it in use. The mass-deviation-rate clause plus the no-weight-adding clause together close this loophole — the fill is weighed at standard atmosphere, and any chemical weight gain is detectable in the oil-content and residue tests.
Do infant silk quilts have stricter requirements?
Yes. An infant silk quilt must meet GB 31701 in addition to GB/T 24252 and GB 18401, which routes it through Category A thresholds: formaldehyde ≤ 20 mg/kg, pH 4.0–7.5, colourfastness to saliva, and no odour. The fill's pH is already tighter (4–8) under GB/T 24252 for all silk quilts, so the infant-specific lift is mainly in the cover's safety category and the saliva-fastness requirement.