When you request a quote for flock fiber, suppliers send back a spec sheet — a short list of numbers like "3.0D × 1.0mm, color fastness 4". If you don't know how to read it, you're buying blind. This guide explains the three most important parameters — denier, cut length, and color fastness — plus a few others you should check before you place an order.
Flock Fiber Spec Sheet at a Glance
| Parameter | What It Measures | Typical Range | Why It Matters |
|---|---|---|---|
| Denier (D) | Fiber thickness | 0.5D – 30D | Determines softness and density of the finish |
| Cut Length (mm) | Fiber length | 0.3mm – 5.0mm | Determines the "pile height" and texture |
| Color Fastness | Resistance to fading/rubbing | 1 – 5 grade | Determines how long the color lasts |
| Fiber Type | Material (nylon/rayon/polyester) | PA / Viscose / PET | Affects durability, feel, and cost |
| Moisture Content | Water absorbed by the fiber | 0.5% – 4% | Affects electrostatic performance and storage |
Denier: How Thick Is the Fiber?
Denier (D) measures fiber thickness. Technically, 1 denier means 9,000 meters of the fiber weighs 1 gram — so a lower denier number means a thinner, finer fiber. This single number has a big effect on how your finished product feels.
Some suppliers (especially European ones) quote thickness in dtex instead of denier — 1 denier ≈ 1.11 dtex. Flock fibers span from ultra-fine 0.5D up to coarse 30D and beyond for specialized uses.
| Denier Range | Feel / Finish | Typical Applications |
|---|---|---|
| 0.5D – 3D (fine) | Very soft, dense, velvety | Apparel, home textiles, jewelry boxes |
| 3D – 6D (medium) | Balanced softness and texture | General flocking, packaging, display |
| 6D – 30D (coarse) | Rough, textured, hard-wearing | Automotive interiors, carpets, industrial seals |
- Rule of thumb: finer denier = softer, denser, more premium feel; coarser denier = more durable and textured.
- Cost note: finer fibers are generally more expensive because they take longer to produce and are harder to flock uniformly.
- Watch out: fibers that are too fine (below ~1.5D) can clump in humid conditions, so anti-static treatment is recommended.
Cut Length: How Long Are the Fibers?
Cut length is the length of each individual fiber after it's been cut from the filament. It controls the "pile height" of your flocked surface — how much the fibers stand up. Standard flocking uses 0.3–3.0mm; longer fibers up to 5.0mm (or more for specialty applications) create a plush, fur-like finish.
| Cut Length | Resulting Texture | Best For |
|---|---|---|
| 0.3 – 0.7mm | Fine, powder-like, subtle | Detailed logos, thin lines, fine printing |
| 0.7 – 1.5mm | Standard velour feel | Most general flocking work |
| 1.5 – 3.0mm+ | Long, plush, fuzzy | Decorative items, toys, soft-touch panels |
- Key principle: fiber length should always be greater than fiber diameter, or the fibers can't stand upright during electrostatic flocking.
- Match to your adhesive: longer fibers need a thicker adhesive film to anchor them securely.
Color Fastness: How Long Will the Color Last?
Color fastness rates how well the dye resists fading, rubbing off, or running. Rubbing (crocking) and washing fastness are graded 1–5 under AATCC/ISO test methods, while light fastness uses the Blue Wool Scale of 1–8. In every case, a higher grade means better color retention.
| Test | What It Checks | Why Buyers Care |
|---|---|---|
| Rubbing / Crocking | Color transfers under friction | Critical for upholstery and apparel |
| Washing | Color bleeds in water | Important for washable textiles |
| Light — Blue Wool Scale (1–8) | Fading under sunlight/UV | Key for outdoor or window-exposed items |
| Sublimation | Dye evaporates under heat | Relevant for automotive (high heat) |
- By material: polyester generally has the best color fastness, nylon is good, and viscose rayon is the most sensitive to water and light.
- What to ask for: the ASTM performance spec for flocked upholstery requires at least grade 4 dry / grade 3 wet crocking. For heavy-use products, aim for grade 4 or higher on both.
Other Parameters Worth Checking
- Fiber type: nylon (PA), viscose rayon, polyester (PET), or modified polyester — this is the biggest driver of feel, durability, and price.
- Anti-static treatment: essential for fine fibers, which otherwise clump during electrostatic flocking.
- Moisture content: affects storage life and electrostatic performance; look for 0.5%–4% depending on material.
- Cross-section shape: round fibers are standard; special shapes (e.g. trilobal) create unique optical effects.
Still Confused by a Spec Sheet?
Send us the spec sheet from your current supplier — or just tell us your application and desired feel — and we'll decode it for you, then recommend the right fiber with samples to match. Contact us here.
Frequently Asked Questions
- What denier is best for a soft, premium feel?
- For a velvety, luxurious touch, choose a fine denier in the 1.5D–3D range. Viscose rayon in fine deniers is the softest option for textiles.
- Does cut length affect how dense the flocking looks?
- Not directly — density is mostly determined by denier and flocking technique. Cut length controls pile height (how long the fibers stand up), not how tightly packed they are.
- What color fastness grade should I require?
- For products that face regular use or washing, require grade 4 or higher on rubbing and washing tests. For outdoor use, also check the light-fastness rating.
- Why does polyester have better color fastness than viscose rayon?
- Polyester fibers are dyed at high temperature during production, which bonds the dye strongly. Viscose rayon is a regenerated cellulose fiber that absorbs moisture and releases dye more easily.