My picture today is of what we call a ‘tow and blow’ machine. One of the many tools used by winemakers to fight frost here in the Loire.
In French we call it a ‘tour anti-gel mobile’. They are efficient for temperatures that drop as low as minus 3°C and are only useful when the frost is radiative. If the wind speed is greater than 8km/h they don’t work.
A radiative frost is when, after the sun goes down, the soil loses heat accumulated during the day. Hot air rises to the sky and the colder more dense air accumulates on the ground. There is generally little wind and clear skies. The percentage of humidity in the air (the dew point) will determine if the frost is a ‘white frost’ where the dew point temperature is greater than 2,2°C and it’s humid or a ‘black frost’ when the dew point temperature is less than 2,2°C and the conditions are dry.
We see these quite a bit around us in the Montlouis sur Loire appellation on the South side of the Loire where they have big problems with frost. This picture was taken in Jacky Blot’s prestigeuse parcel, the Clos de la Bretonnière just up the hill from us here in Noizay.
To install something like this requires an investment of around 30,000€ for 3 hectares of land and they cost around 100€ a hectare to run. It’s a big investment and this is the only one I have seen within the Vouvray appellation (although ironically, the wine from this parcel is sold under the Table Wine category as Jack Blot’s winery is not within the zone for it to be classed as Vouvray appellation).
