One of the biggest changes in cognac production in the 19th century was the change of grape from the Folle, or Folle Blanche as we know it today, to the Ugni Blanc after the Phylloxera outbreak in 1872. The Cognaçais were, in effect, forced to try and understand their viniculture on a more sophisticated level. By controlling crop levels, so as to reduce stress on the new roots, controlling disease and the timing of harvesting the grapes, the quality of the wine improved and therefore the cognac.
The clearer thinking on viniculture also rubbed off on the viticulture and the ageing process. The introduction of wine warmers, different still shapes and sizes, time controls on the grapes before pressing to avoid bacteria and the use of lees to add flavour were all part of the rapid learning which added more attractive qualities to the spirit. As skill and knowledge of the distillation process improved, so too did understanding of the ageing process. Cellar masters began learning about the effect of the barrels on the quality of the cognac. Barrels could be made from different oaks, in various sizes and perhaps most importantly, if stored in damp cellars spirit migration could be controlled.