The most important breakthrough came in 1429 when corning was first carried out in France. Briefly the process consisted of moistening the mixture, pressing the paste so formed into 'cakes', drying them, then breaking them up into smaller particles called grains. Various moistening agents were tried, including wine, vinegar and urine. Monks' urine was said to be the best, with bishops' the 'creme de la creme'.

This was a typical example of mediaeval thinking. Because the clergy generally enjoyed a higher standard of living than other folk, therefore their urine was thought to be of higher quality. Eventually pure water was found to be the best moistener.

Corning thus formed a much more intimate mixture with the following advantages:

1. Vibration had little effect on it; the ingredients no longer separated out during transport.
2. The grains were less susceptible to the effects of moisture.
3. The gaps between the grains enabled flame to pass more freely, making the rate of burning more consistent.
4. Variations in loading conditions did not affect the rate of burning to the same extent.
5. Corned powder was found to be at least 30% more powerful than serpentine.