Crepe rubber is made by passing coagulated rubber repeatedly between rollers under running water, so that dirt, serum and colour wash out, then drying the thin lace-like sheet in the air with no smoke. The result is a paler, cleaner rubber than smoked sheet, used where light colour or low contamination matters. Because the rollers must pull a heavy mass through a nip, the rollers need a stop the operator can reach with the free hand.
Part of Rubber Processing
Washing and milling coagulated rubber into pale sheet instead of smoking it.
Washing And Milling Replace Smoking When Colour Matters
The carrier names crepe as the route to lighter-coloured rubber, by washing and sheeting. The corpus holds no schedule, thickness, water volume or drying time for crepe, so this article is qualitative. The method is general rubber-trade practice (recalled, not from the corpus) and the working settings need to be found by trial.
| Route | Treatment | Result |
|---|---|---|
| Smoked sheet | Rolled thin, smoked 5-7 days | Amber to brown, long storage; see Smoke Curing (RSS) |
| Crepe | Washed and milled under water, air-dried | Pale, clean, lace-like sheet |
What You Need
- Coagulum from Acid Coagulation, before any smoke.
- A roller mill with the rollers close enough to pull the mass through; a hand-cranked mill is enough for small batches. See the safety discussion in Compound Mixing.
- A supply of clean running or poured water over the nip.
- A shaded, airy drying rack, out of direct sun, since the carrier warns that raw rubber degrades in sunlight.
Method: Making Crepe
Step 1: Pass the coagulum between the rollers repeatedly, narrowing the gap each time.
Step 2: Keep water running over the sheet so that serum, dirt and bark wash away.
Step 3: Fold and re-pass until the sheet is thin and lace-like and the wash water runs clear.
Step 4: Hang to dry in shade with plenty of air, with sheets not touching.
Step 5: Dust and store dry and cool, with talc or chalk against sticking, as for other raw rubber in Latex Processing.
Common Mistakes
- Drying in direct sun. It degrades the rubber and yellows the sheet.
- Washing too little. Residual serum spoils in storage and shows as dark patches.
- Feeding by hand into the nip. See the danger block.
Safety
The nip pulls in the hand and no one can stop it from the other end
Two rollers pulling a rubber mass draw a hand or sleeve in at once, and wet rollers and wet hands make it worse. The operator’s own reach is the only safety system unless a stop exists: fit a bar across the front of the rollers at hand height, connected to a lever that throws the drive belt off or declutches the drive, and measure how long the rollers take to stop after release. With a hand-cranked mill, take both hands off the crank only after the rollers have stopped. Never feed with fingers; use a wooden paddle.
What’s Next
- Learn next: Compound Mixing — the mill used for compounding
- Combine with: Sulfur Vulcanization — curing the rubber you have made