For those who have bought too much ginger root.
Friendly warning: does not taste good to everyone!
Scrape ginger root into a large baking bowl, pour in lime slices, tartaric acid and sugar.
Heat a mug of water and pour over the yeast.
Bring the rest of the water to a boil and pour over the ginger mixture. When this has become lukewarm, whip the yeast into a paste and stir it in.
Cover and let stand for 2 days. Strain and bottle.
The ginger beer will keep in the refrigerator for up to a week.