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What is Wet Polishing?

As I write this, the London robusta futures market is seeing record highs. The reasons behind this are mainly linked to reduced supply in Vietnam. This was driven by the contracting of coffee as prices continuously rose in 2023 until supply failed to meet the demand.  Farmers withheld crops in anticipation of higher prices, which they got and then sold thinking that was the top. The demand continued, with contracts made on the assumption there was always something available. This year has also seen around a 10% reduction in production, furthering the squeeze. Demand’s high, and the previously thought of bottomless supply has found a boundary.

The growth of speciality robusta continues, and combined with the headlines from the commercial side,  we have more attention on robusta than previously seen. This has meant a lot of people have been introduced to a peculiarity of Vietnam robusta (not exclusively, but still) and that is Wet Polishing. But what exactly is polishing?

Green beans as we know will have silverskin attached as part of the make up of the bean. For most people, this is removed as chaff in the roasting process and generally has little impact on the actual roasting process. For buyers of Robusta though, the removal of this through polishing is a thing that some very much demand and will pay a premium for.

A small step in the process, coffee is picked dried and hulled as usual, graded through size graders, gravity separators and colour sorters as required, and then added to a chamber where a small amount of steam or hot water is introduced. Not enough to significantly dampen the beans, but enough to make the silverskin attached moist and ‘sticky’. The beans are agitated during this and the silverskin, through friction, is rubbed off the beans, leaving them cleaner, and slightly shiny. The heat is no more than the bean would experience when drying via a mechanical drier, and the moisture is so minimal that any increase is evaporated off in that heat generated through friction.

Robusta Processing, Vietnam