A distinct characteristic of Rioja wine is the effect of oak aging. First introduced in the early 18th century by Bordeaux influenced winemakers, the use of oak and the pronounced vanilla flavors in the wines has been a virtual trademark of the region though some modern winemakers are experimenting with making wines less influenced by oak. Originally French oak was used but as the cost of the barrels increased many bodegas began to buy American oak planks and fashion them into barrels at Spanish cooperages in a style more closely resembling the French method. This included hand splitting the wood, rather than sawing, and allowing the planks time to dry and "season" in the outdoors versus drying in the kiln. In recent times, more bodegas have begun using French oak and many will age wines in both American and French oak for blending purposes.