Preparing the yeast starter and siphoning
You require a yeast type depending on the type of beer you want to obtain. If you are to use a WYEAST yeast, for a quantity of 20 litres of wort you do not have to make a special starter (with the WYEAST package XL you start up to 40 litres of wort). Follow the instructions for use for this yeast type (it may be the case that you have to start this earlier). If however you use the yeast grain (dry yeast) you must create a starter beforehand. This is because fermentation must start quickly, again to reduce the likelihood of infection. During the first days of fermentation carbon dioxide gas forms, as does alcohol little by little, and it is this abundance of carbon dioxide that can prevent an infection. You can best make the starter the day previous to or on the morning of brewing. To do this boil a sugar solution for 15 minutes (about a smoothed tablespoon of sugar in 250ml water) so it is sterile. When this solution has cooled to 25°C, pour it into a glass or fermentation bottle and add the dry yeast. Make sure that all yeast is dissolved. Cover the glass with some foil, or the fermentation bottle with the cap, and put at room temperature. After several hours the fermentation will normally already start. You can see this by the rising air bubbles in the solution and the formation of foam.
After the wort is cooled by the plate heat exchanger till about 25°C, you can measure the density for the first time : fill the measuring glass with wort. A correct density measurement is carried out at a temperature of 20°C. Carefully place the densimeter (hydrometer and densimeter are synonyms) in the measuring glass and read off the density (for beer this normally lies between approximately 1050 and 1100, but can sometimes differ slightly). Write this figure down together with the date of measuring. This is your initial density.