This home-brew remains a favourite party drink in a Welsh household for both adults and children. You will need eight pint bottles or four quart bottles. They should be of a strong material and have firm caps with metal springs to imprison the effervescent liquid it's more explosive than champagne. Makes 1 gallon. Roughly crush the ginger root. Wash and slice the lemons into thick rings. Put the ginger, lemon, cream of tartar and sugar in a large bowl. Pour the boiling water over. Stir and leave to cool to blood temperature. Stir in the yeast. Leave to ferment for 24 hours. Skim off the yeast. Strain and bottle the liquid. Leave for three days before broaching it.