In the 1830s, Aeneas Coffey refined a design originally created by Robert Stein for a continuous still which produced whisky much more efficiently than the traditional pot stills, but with much less flavour. Quickly, merchants began blending the malt whisky with the grain whisky distilled in the continuous stills, making the first blended Scotch whisky. The blended Scotch proved quite successful, less expensive to produce than malt with more flavour and character than grain. The combination allowed the single malt producers to expand their operations as the blended whisky was more popular on the international market. As of 2004, over 90% of the Single Malt Scotch produced is used to make blended Scotch.