Ribbed Smoked Sheets, or air dried sheets are commonly known as RSS. It can be graded into RSS1 to RSS5, with RSS1 as top grade. It is usually packed in large bales of 111.11kg/bale or 19 metric tons per 20 foot FCL.
The different grades are determined by the percentage of particles in the rubber sheet.
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| Grade | Unacceptable Conditions | Acceptable Conditions |
|---|---|---|
| RSS1 | Oxidized spots, weak heated, under-cured, over-smoked, opaque and burnt sheet are not acceptable. | Slight traces of dry mould on the packaging are acceptable but mould should not penetrate inside the bale. Small scattered pinhead bubbles are permissible. |
| RSS2 | Oxidized spots, weak heated, under-cured, over-smoked, opaque and burnt sheet are not acceptable | Slight traces of rust and dry mould on the packaging and interior sheets are acceptable but it should not be >5% of the bales sampled. Small bubbles and slight specks of bark are permissible. |
| RSS3 | Oxidized spots, weak heated, under-cured, over-smoked, opaque and burnt sheet are not acceptable | Slight traces of rust and dry mould on the packaging and interior sheets are acceptable but it should not be >10% of the bales sampled. Small bubbles, slight specks of bark, slight blemishes in colour are permissible. |
| RSS4 | Oxidized spots, weak heated, under-cured, over-smoked (exceeding the degree shown in samples), opaque and burnt sheet are not acceptable |
Slight traces of rust and dry mould on the packaging and interior sheets are acceptable but it should not be >20% of the bales sampled. Medium sized black particles, bubbles, translucent stains, slightly sticky or over-smoked rubber are permissible. |
| RSS5 | Oxidized spots, weak heated and burnt sheet are not acceptable | Slight traces of rust and dry mould on the packaging and interior sheets are acceptable but it should not be >30% of the bales sampled. Large particles, bubbles or barks, small stains or blisters, slightly sticky, slightly under-cured or over-smoked rubber, blemishes are permissible. |
Air Dried Sheet
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This is a light colored sheet prepared under closely controlled conditions in the same way as Ribbed Smoke Sheet but dried by air usually in a shed or tunnel without smoke or additives other than those generally accepted, such as sodium bisulphate and paranitrophenol.
The rubber must be dry, clean, strong, sound and free from blemishes, resinous matter (rust), blisters and any foreign matter except slight specks as shown in samples. Small pinhead bubbles, if scattered, will not be objected to.