Direct answer
BSF.T fibre — a PBT (polybutylene terephthalate) specification — is what FanLash produces with, and it is the fibre most professional eyelash extension manufacturers use for volume fans, classic trays and premade fan styles. It holds a curl through steam and daily wear better than earlier fibre types, keeps a consistent diameter across the tray, and stays light enough for high-density volume work. When you approve a wholesale sample, what you are really checking is the BSF.T grade, the curl-set process and the fan base integrity control — not the marketing name on the box.
What BSF.T actually means for a lash buyer
Most sellers describe lashes as “mink”, “silk” or “cashmere”. These are finish and feel descriptions, not fibre chemistry. The underlying raw material for nearly all professional volume lashes is BSF.T. Understanding that distinction helps you ask better questions during sample approval and avoid paying a premium for a label instead of a material difference.
| Term you see | What it really describes | What to verify in a sample |
|---|---|---|
| BSF.T | The base polymer fibre | Curl retention after steam, diameter consistency across rows |
| Mink | A finish and softness description | Whether the finish is matte or glossy, and how it behaves under salon light |
| Silk | Usually a lighter, softer matte feel | Weight, density at 0.05 and 0.07, whether fans hold shape |
| Cashmere | A premium soft-matte positioning | Colour depth, softness, and whether it is a genuine different fibre or a renamed grade |
Four checks that separate good BSF.T from average BSF.T
Two trays can both claim BSF.T and still perform very differently. These four checks are what actually differ.
01 Curl retention after steam
Hold a fan over a kettle or use a steamer for a few seconds and see whether the curl returns to its original shape. Well-set BSF.T recovers; lower-grade fibre opens or relaxes and stays that way. This single test predicts how the lash behaves for a client after a hot shower.
02 Diameter consistency across the tray
Take lashes from the first row, the middle and the last row and compare them side by side under good light. Production tolerance problems show up as visible variation in thickness, which changes how fans bloom and how heavy the completed set feels.
03 Root fan base integrity control
Look at the base of a premade fan. A controlled glue dot is small, even and sits at the base without climbing the fibres. Excessive glue feels bulky on the natural lash and causes the fan to splay during pickup.
04 Fan opening and pickup
Ask an artist to pick ten fans off the strip. They should release cleanly without collapse, twisting or base damage. If pickup requires re-shaping, that is a handling cost your salon pays on every set.
How to write a BSF.T specification you can reorder against
The most common cause of quality drift between orders is not a change of factory — it is an incomplete written specification. When you approve a sample, record these fields and keep the approved tray as a physical reference:
- Fibre type and finish — BSF.T grade, matte or glossy
- Curl — letter designation plus the curl-set method if the factory can state it
- Diameter — exact mm values used across the range
- Length mix — the specific rows in the tray
- Fan dimension — D count for volume and premade products
- Tray format — single tray or mixed tray, row count
- Packaging version — label artwork, box type, SKU naming
With that record, a reorder can be checked against something concrete rather than a memory of “the soft ones from last time”.
Common mistakes when sourcing BSF.T lashes
Judging quality from one row. The top row of a tray is often the most carefully placed. Always sample from the middle and the end.
Comparing trays without controlling variables. If you change curl, length and diameter at the same time, you cannot tell which change caused the difference. Approve one specification at a time.
Paying for a label instead of a material. “Mink” and “cashmere” are useful positioning words, but they are not a fibre specification. Ask what the base fibre is and test curl retention yourself.
FAQ
Is BSF.T safe for eyelash extensions?
BSF.T is the conventional fibre used across the professional lash industry. Product suitability depends on correct application, patch testing and aftercare by the lash artist. Buyers should check local regulatory requirements for cosmetics in their market before making claims on packaging.
Is BSF.T better than synthetic “mink” lashes?
Most “mink” lashes are also BSF.T with a particular finish and marketing name. The meaningful comparison is curl retention, diameter consistency and fan base integrity control — all of which you can test in a sample.
How many times should I test a sample before a bulk order?
Test with at least two artists and several sets if you can, and compare the middle and end rows of the tray rather than only the samples on top.
Can I private label BSF.T lashes?
Yes. Tray labels, boxes, insert cards and SKU naming can all carry your brand. Approve packaging artwork together with the product specification so both are locked before production.
Related pages
- Premade Fans Wholesale (4D–12D) — compare densities, stems and tray formats
- Lash Specification Guide — curl, length and thickness explained
- Sample Kits — test quality before bulk production
- Our Factory & QC — how production and inspection work
Test BSF.T quality before you commit to a bulk order
Request a sample kit and compare curl retention, diameter consistency and fan base integrity control yourself.