The two rubbers diverged today. Natural rubber closed at ¥18,980/t, down 2.44% on the day; butadiene rubber at ¥15,440/t, off only 0.55%. The spread stretched from the ¥3,200 area last week to ¥3,540/t — natural rubber is once again the expensive leg.

For tire makers this is a formulation problem. When NR is dear and BR is cheap, recipes shift BR up and NR down, and each unit swapped shaves a few fen to a dime of cost. Once the spread clears ¥3,500, that substitution pays, and we see downstream enquiries tilting toward butadiene rubber.

The second thread is financing. Both NR and BR open as bonded digital warrants; once on-chain, a SHA-256 browser-side fingerprint fixes batch title, and pledge lending drops from T+3 to T+0. At ¥18,980, a 5kt natural-rubber warrant releases about ¥94.9m of tied-up capital before haircut; the butadiene sheet about ¥77.2m. A wider spread does not change the pledge logic, but it shifts which warrant traders prefer to pledge — the cheaper butadiene turns faster.

We watch the NR-BR spread next to the warrant pledge ratio. A widening spread says downstream is rebalancing recipes and BR demand is picking up; a moving pledge ratio says merchants are freeing working capital. Together they read rubber activity better than either price alone.