Clonal selection and improved cultivation considerably increased the yield of the vineyards in the 1970s.
The yield of must was further increased by the new pressing methods which extracted a higher proportion of the available juice from the grapes.
These factors alone would no doubt have resulted in a lowering of the concentration and consequent alcoholic degree of the musts but there is the further influence of the abandonment of sunning.
The combined result of all these things is that musts got to be about a degree weaker than they used to be, though extensive tasting sessions persuaded wine tasters that the mature wines (which grow in strength as they mature) were as good as ever.
The typical strength of a newly fermented wine such as a Petite Sirah or Grenache would be 11°-12°.
There was one unfortunate consequence, though in that there was a higher rate of failure than before so that more casks of must had to be rejected.
Another factor that played a part in this is that the average age of the vineyards was lower than before owing to expansion and replanting.
In the old days it was hard to find a cask of must poor enough to be used for feeding the bodega's vinegar solera.
That problem eventually diminished but the rejection rate was low enough not to matter, as in most years the producers had, by government decree, to give 7 percent of what they produced for distillation and there were scarcely enough reject butts for this purpose.
The maximum yield allowable per hectare was eighty hectolitres for Jerez Superior and one hundred hectolitres for the rest.
The Consejo Regulador had a representative permanently by each press to check the amount of must made.
In some years of immensely high yield, a grower could apply for his extra yield to be classified and when this happened a decision was made about an individual vineyard, taking into consideration the yield in the area as a whole.
Usually these applications came from small, peasant growers who had cultivated their plots intensively.
If over-production was found, however, the whole output of the vineyard was condemned and could not be used for sherry, Riesling, Muscat [http://www.
wineaccess.
com/wine/grape/Muscat], or any other wine.
When the vintage was over and all was at peace, the wine growers started a new year of work.
The must was stored in the bodegas of the three sherry towns, where the horrible smell of fermentation greeted the visitors wherever they walked.
The must was the life blood of the bodegas; it was continually examined and checked, as everything depended on it.
By the end of September, there was fermenting must in every possible corner of the sherry towns, and you could not walk through the streets for more than a few minutes without coming across the sickly, vegetable smell of fermentation; it was one of the necessary evils.
The casks of slowly fermenting must were not sealed against the atmosphere but were protected against dirt and dust by wooden stoppers that rested on top and fit loosely into the holes.
The fermentation tanks had valves that achieved the same effect, so that air could get in quite easily and carbon dioxide, evolved in the course of the fermentation, could get out.
They were also left on ullage, which meant there was an empty space above the wine.
Fresh air had to be able to circulate freely around the casks to help keep the temperature down, and the carbon dioxide generated by the fermentation needed to be able to escape, so the obvious place to store them was outside in the open, or in a building with open sides like a Dutch barn.
On the other hand, the temperature of fermentation had to be kept low, and this called for the cool atmosphere of a bodega rather than the warm sunshine of an Andalusian autumn.
Both methods were quite satisfactory provided the storage patio was well shaded and the bodega had open windows to encourage a good draught with open doors or holes at floor level to let the carbon dioxide escape.
Particularly for wines that required a cooler atmosphere, like Pinot Noir, Malbec, or Merlot, an area with plenty of fresh air and cool breezes was necessary.
Shippers who suffered from lack of space praised the open air, while those with plenty of buildings used them.
Everyone was unanimous in avoiding exposure to direct sunlight, and more bodegas were built for maturing must as funds and land became available, so it appeared on balance that this was slightly the better alternative, but there was not much in it when casks were used.
The more modern fermentation tanks were of course permanent installations in buildings.
The yield of must was further increased by the new pressing methods which extracted a higher proportion of the available juice from the grapes.
These factors alone would no doubt have resulted in a lowering of the concentration and consequent alcoholic degree of the musts but there is the further influence of the abandonment of sunning.
The combined result of all these things is that musts got to be about a degree weaker than they used to be, though extensive tasting sessions persuaded wine tasters that the mature wines (which grow in strength as they mature) were as good as ever.
The typical strength of a newly fermented wine such as a Petite Sirah or Grenache would be 11°-12°.
There was one unfortunate consequence, though in that there was a higher rate of failure than before so that more casks of must had to be rejected.
Another factor that played a part in this is that the average age of the vineyards was lower than before owing to expansion and replanting.
In the old days it was hard to find a cask of must poor enough to be used for feeding the bodega's vinegar solera.
That problem eventually diminished but the rejection rate was low enough not to matter, as in most years the producers had, by government decree, to give 7 percent of what they produced for distillation and there were scarcely enough reject butts for this purpose.
The maximum yield allowable per hectare was eighty hectolitres for Jerez Superior and one hundred hectolitres for the rest.
The Consejo Regulador had a representative permanently by each press to check the amount of must made.
In some years of immensely high yield, a grower could apply for his extra yield to be classified and when this happened a decision was made about an individual vineyard, taking into consideration the yield in the area as a whole.
Usually these applications came from small, peasant growers who had cultivated their plots intensively.
If over-production was found, however, the whole output of the vineyard was condemned and could not be used for sherry, Riesling, Muscat [http://www.
wineaccess.
com/wine/grape/Muscat], or any other wine.
When the vintage was over and all was at peace, the wine growers started a new year of work.
The must was stored in the bodegas of the three sherry towns, where the horrible smell of fermentation greeted the visitors wherever they walked.
The must was the life blood of the bodegas; it was continually examined and checked, as everything depended on it.
By the end of September, there was fermenting must in every possible corner of the sherry towns, and you could not walk through the streets for more than a few minutes without coming across the sickly, vegetable smell of fermentation; it was one of the necessary evils.
The casks of slowly fermenting must were not sealed against the atmosphere but were protected against dirt and dust by wooden stoppers that rested on top and fit loosely into the holes.
The fermentation tanks had valves that achieved the same effect, so that air could get in quite easily and carbon dioxide, evolved in the course of the fermentation, could get out.
They were also left on ullage, which meant there was an empty space above the wine.
Fresh air had to be able to circulate freely around the casks to help keep the temperature down, and the carbon dioxide generated by the fermentation needed to be able to escape, so the obvious place to store them was outside in the open, or in a building with open sides like a Dutch barn.
On the other hand, the temperature of fermentation had to be kept low, and this called for the cool atmosphere of a bodega rather than the warm sunshine of an Andalusian autumn.
Both methods were quite satisfactory provided the storage patio was well shaded and the bodega had open windows to encourage a good draught with open doors or holes at floor level to let the carbon dioxide escape.
Particularly for wines that required a cooler atmosphere, like Pinot Noir, Malbec, or Merlot, an area with plenty of fresh air and cool breezes was necessary.
Shippers who suffered from lack of space praised the open air, while those with plenty of buildings used them.
Everyone was unanimous in avoiding exposure to direct sunlight, and more bodegas were built for maturing must as funds and land became available, so it appeared on balance that this was slightly the better alternative, but there was not much in it when casks were used.
The more modern fermentation tanks were of course permanent installations in buildings.
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