Why Silk Grade Is the First Thing You Should Look For
When you invest in silk sheets or silk bedding, you're making a purchase that goes far beyond aesthetics. You're choosing a fiber with a centuries-long history of luxury , one that is softer, smoother, and more temperature-regulating than virtually any other natural material available. But not all silk is created equal. And the difference between a truly exceptional silk sheet set and a mediocre one often comes down to a grading system that most consumers have never heard of. Mulberry silk is widely recognized as the finest silk on earth. It comes from the cocoons of Bombyx mori silkworms, a specific species raised in carefully controlled environments and fed exclusively on the leaves of the mulberry tree. That controlled diet and environment produce silk filaments that are finer, smoother, and more consistently colored than any other variety. In fact, mulberry silk fibers are so remarkably strong that, strand for strand at the same diameter, they are stronger than steel. But even within the world of mulberry silk, quality varies. That's where the grading system comes in.
Understanding the International Silk Grading System
Silk grading is not arbitrary or brand-specific. It conforms to a recognized international standard developed in the years following World War II by the International Silk Association (ISA). As one of the most authoritative textile references on the subject explains:
“Raw silk is classified according to an international system drawn up by the International Silk Association (ISA) in the years following the Second World War. Representatives of the main producer and consumer countries formed a ‘Classification Committee’ and agreed on the international system, which is the worldwide standard, although some minor differences may exist in certain national classification systems. There are 11 grades in the international classification system, ranging from 6A (the top) through 5A, 4A, down through F.”
— Franck, Robert R. (Ed.), Silk, Mohair, and Other Luxury Fibres, The Textiles Institute, Woodhead Publishing Limited, Cambridge, England, p.25
This matters enormously for anyone shopping for real silk bedding. The grading system provides a universal, objective language for silk quality, one that every reputable manufacturer, textile scientist, and industry professional recognizes. When a silk bed linen brand uses this system correctly and transparently, you can trust what you're buying. When a brand deviates from it — or invents grades that don't exist within the international standard — that's a signal to proceed with caution.
Breaking Down the Silk Grade Scale: Letters and Numbers
Silk is graded first by letter and then by number. Together, those two designations tell you nearly everything you need to know about the quality of the fiber inside your silk sheets or mulberry silk pillowcase.
The Letter Grades: A, B, and C
The letter grade is the foundation of the system and reflects the fundamental character of the silk fiber itself: length, purity, and national color. Grade A is the highest letter classification. It refers to silk produced from the outermost filaments of the cocoon, where the worm's spinning is at its most refined. These are the longest, least interrupted strands, the ones that can be unwound to remarkable lengths without breaking. Grade A silk is notably pure, meaning it contains minimal debris or short-fiber contamination, and it presents in a clean, luminous ivory-white that is the hallmark of top-tier raw silk. When you run your hand across a Grade A silk sheet set, that gliding, frictionless feel is a direct result of what this letter grade represents. It's also why Grade A silk is particularly well-suited for people with sensitive skin ; the purity and smoothness of the fiber mean less friction and fewer irritants against delicate complexions.
Grade B sits in the middle of the scale. The filaments here are shorter and less uniform, which means the finished fabric carries more joins — places where shorter strands connect — which translates to subtle texture inconsistencies and a less lustrous surface. Grade B silk isn't without its uses, but it falls noticeably short of the smoothness and durability that luxury silk bedding demands. Grade B silk is best suited for things like upholstery, crafts, some apparel, and home decor.
Grade C represents the lowest tier of commercial silk. Produced from the innermost strands of the cocoon, Grade C fibers are the shortest, weakest, and most impure. The characteristic yellowish tone associated with lower-grade silk comes from these inner filaments, which carry higher concentrations of sericin and other impurities that can't be fully processed out. If you've ever touched a piece of silk that felt rough, looked dull, or pilled after minimal use, Grade C fiber is very likely the culprit. Grade C silk can be found in low-quality budget bedding and fast fashion.
The Number Grade: From 2A to 6A
Within Grade A — where all premium bed sheets, silk pillowcases, and silk bedding should originate — quality is further refined by number. The scale runs from 2A at the lower end up through 3A, 4A, 5A, and finally 6A at the very top. Grade 6A is the pinnacle of the international grading system. It represents the longest, strongest, and purest silk filaments available anywhere in the market. The fibers are pearly white, uniform, and capable of being processed into the kind of smooth, durable, luminous fabric you find in the finest silk bedding. A silk sheet set or fitted sheet made from Grade 6A mulberry silk will feel noticeably different from anything below it; softer against the skin, more even in its sheen and luster. The same holds true for a Grade 6A silk duvet cover or a 100% mulberry silk pillowcase — the grade elevates every product it goes into. All Mulberry Park Silks bedding and accessories are made from Grade 6A silk. Grades 5A and 4A are generally very good materials. For most applications, they would be considered high quality. But compared side by side with 6A, there are measurable differences in the uniformity of the filament, the consistency of the color, and the overall luster of the finished fabric. These differences may be subtle to the casual observer, but they become apparent in the long-term performance and feel of your silk bedding. As you move down the numerical scale, each step represents shorter filaments, slightly more variation in fiber quality, and incrementally less of that signature silk luminosity. That difference in quality is why Mulberry Park Silks won’t ever compromise on our silk grade; our clients deserve only the best.
Why This Matters for Your Silk Bedding Purchase
Understanding the grading system changes the way you shop. Rather than relying on vague descriptors like "luxury" or "premium" — words that carry no standardized meaning — you can ask a straightforward question: what grade is this silk? Keep the following in mind:
- The finest silk fabric in the world is produced in China from mulberry silk fiber, valued for its superior strength, durability, and lustrous hand feel.
- When that fiber is graded 6A and woven into bedding at an appropriate momme weight, the result is a product that delivers on every promise silk has ever made: temperature regulation, moisture management, a gentle surface to protect skin and hair (especially in comparison to cotton ), and a beauty that lasts.
- Whether you're shopping for bed sheets, a pure silk pillowcase, or a complete silk duvet cover, the grade is what determines whether that promise is kept.
At Mulberry Park Silks, we use only 100% pure mulberry silk, Grade 6A. From our silk sheets (sets, or a la carte fitted sheets, and flat sheets) to our best-selling mulberry silk pillowcases and duvet covers to our lounge robes and sleep masks, silk scrunchies, glam bands, headbands, and sleep bonnets. Whether you're building out your bed linen collection piece by piece or taking advantage of our bedding bundles, Grade 6A is not reserved for any one category; it is the standard we hold across everything that carries the Mulberry Park Silks name.
A Note on Silk Grades That Don't Exist
No discussion of silk grading would be complete without addressing a growing source of consumer confusion: so-called "Grade 7A silk." No such grade exists within the international silk grading standard. The ISA classification system tops out at 6A. There is no 7A, and any brand using that designation is operating outside the bounds of the recognized global standard. When shopping for silk bedding or silk accessories, if you encounter a "7A" claim, treat it as a red flag rather than a selling point. "When our customers understand silk grading, they shop with real confidence," said Kendra Cosenza, Senior Brand Manager at Mulberry Park Silks. "Grade 6A isn't a marketing term — it's an internationally recognized standard, and it's the only grade we use across every silk product we make. We believe you deserve to know exactly what you're investing in, and Grade 6A is simply the best there is."
Other Things to Keep in Mind When Purchasing Quality Silk Sheets, Pillowcases, and Bedding
When grade and fiber quality are your foundation, a few additional factors help ensure you're getting the very best value for your silk bedding dollar:
- Momme weight matters. The weight of silk fabric — measured in momme — tells you how dense and durable the weave is. Look for a momme weight clearly disclosed in the product listing. At Mulberry Park Silks, our sheets are available in 19, 22, and 30 momme, with each weight clearly labeled so you always know exactly what you're purchasing.
- Certification means safety. Silk is naturally hypoallergenic and resistant to dust mites , mold, and fungus, making it an exceptional choice for sensitive skin. At Mulberry Park Silks, we've taken that extra step to ensure every product is OEKO-TEX® Standard 100 certified, independently tested, and guaranteed safe from more than 1,000 harmful substances, toxins, and irritants. Additionally,our silk has been proven by science to create less friction than cotton.
- Design details make a difference. Closure type, seam construction, and fitted sheet pocket depth all affect how your bedding feels and performs over time. Mulberry Park Silks pillowcases feature French seams and your choice of zipper or envelope closure. Our flat sheets feature a cuff, and our fitted sheets are generously sized to fit deeper mattresses.
- Transparency is non-negotiable. If a product listing doesn't clearly state the silk grade, momme weight, and fiber content, don't buy it. At Mulberry Park Silks, every one of those details is front and center in every product listing, every time. Mulberry Park Silks is a US-based company with headquarters, warehouse, and customer service proudly located in Branford, CT. We provide real-time, personal customer service from a team of silk professionals (as opposed to the offshore operations of most silk companies).
Mulberry Park Silks is Here to Help
Choosing the right silk bedding is an investment, and the Mulberry Park Silks team is available to answer your questions. Whether you're comparing momme weights, exploring our bedding bundles, shopping for a pure silk pillowcase or silk duvet cover, or simply want to know more before you buy. Reach us at (800) 860-1924 Mon-Fri 9:30-5:30 EST or send us a Live Chat at MPSILKS.com.