Submerge the other end of the tube in a cup or bottle with a little water to complete the air lock. Plastic tubing is inexpensive at any home center store, in a variety of sizes. The big yellow pickle buckets can also be used. They are cheap and don t require an airlock because the lid doesn t fit tightly. However, there is a small risk of contamination with a loose lid, and fermentation activity can t be easily observed without an airlock.
Warm temperatures are often a problem in southern Japan.
Warm fermentation can cause poor flavor and aroma, and increases the chance of bacterial contamination. If you have this problem, try the wet T-shirt method. Apparenly it can reduce wort temp by up to 10 degrees Fahrenheit if maintained continually. Set the fermenter in a large, shallow tray. Fill the tray with water and put a cotton T-shirt over the fermenter.