Dissolve the citric acid in 50g of water and slowly mix it with the milk. As soon as the acid has mixed in, add the yogurt, stirring slowly. Then bring the milk to 37 degrees and slowly add the 25 drops of rennet. Leave to rest for 45 minutes. Once this is done, make horizontal and vertical cuts forming 5*5 squares. Wait another 15 minutes and whisk the squares into the size of a cherry stone. Leave to rest for another 10 minutes. After 10 minutes the empirical test is done (you try to make it spin). If it spins you can proceed with spinning. Put 30 grams of salt per liter of water and bring to around 90 degrees.