Sheet Surface Finish
Executive summary
Calendered fashion sheet arrives with a face you did not form. Some catalogs list gloss and matte, or a shinier face and a duller back. Powder after storage is often wax bloom: wax that migrated to the surface. It is a temporary ozone shield, not shop dirt.
Use this when you are reading a roll before print or glue, or when stored sheet looks dusty. Storage and aging sit in Aging, Storage and Care.
You buy the face
What does calendered mean?
Calendered latex sheet is pressed to even thickness between heated rollers at the factory. Both faces come out of that mill process. You buy the finish. How the sheet was made is in Calendered Sheet.
Some vendor menus describe a polishable upper and a roughened underside. Treat that as catalog language. Ask which face they mean. A dull side is not automatically the glue side. Run a bond coupon if the join matters.
Bloom after storage
What is wax bloom?
Wax bloom is antidegradant wax moving to the rubber surface. Industrial compounds use microcrystalline wax at 0.5–1.0 phr to build a surface film that protects against static ozone. Flexing and stretching crack that film. The powder can look like chalk or leftover dust. Peer work on NR bloom treats it as a migrating layer, not leftover talc.
What does phr mean?
phr is parts per hundred rubber. 1.0 phr means one part of that ingredient for every 100 parts rubber in the compound.
What is ozone?
Ozone (O₃) is a reactive form of oxygen that cracks rubber. Wax bloom is a temporary surface barrier for film that sits still. It is a poor plan for a piece that will flex in wear.
Wiping the powder off can bring tack back if the bloom was the only ozone shield. A different surface class: some dark compounds use PPD antiozonants, which can stain. That is not bloom.
Tack on bought sheet
Talc is temporary de-tack for handling. It does not permanently change the rubber face.
If tack returns after a wipe, the usual reading on stored film is that you removed bloom.
Reading cues
| What you see | Think first |
|---|---|
| One side glossy, one dull | Vendor finish menu. Test a glue coupon before you pick a “glue side.” |
| Powder after storage | Wax bloom. |
| Tack after a wipe | Bloom came off. |
Deep dives (optional)
Deep dive: Wax bloom timing
Industrial guidance allows bloom time before ozone exposure. One handbook example: weeks at 23°C and 50% relative humidity in kraft wrapping. Dynamic wear defeats the wax barrier. Antiozonant PPD routes are a different class, used on flexed dark goods.