Uploaded September 2019 | Updated September 2026, 1 week ago
Homemade kefir - choose your method!
Equipment: 3L milk, kefir starter culture, 3 tsp sour cream, 50 mL store-bought kefir, 1L glass bottles, gauze, rubber band, tile, pot.
Pour 3L milk into a pot and bring to a boil. This eliminates unnecessary bacteria. Let cool to room temperature and divide into three clean 1L glass bottles. Add the components that turn milk into kefir: add store-bought starter culture to the first bottle, 3 tsp sour cream to the second bottle, and 50mL store-bought kefir to the third bottle. Mix thoroughly and cover each bottle with gauze. Leave the bottles in a cool, dark place for 12 hours. Your delicious, homemade kefir is ready!
Kefir is a popular fermented milk product obtained via acidic and alcoholic fermentation. It’s usually made by adding a symbiotic culture of milk bacteria and yeast to milk in order to convert lactose, or milk sugar, into lactic acid and complete the fermentation process. Lactose is a disaccharide found in milk consisting of glucose and galactose fragments. Under the influence of lactic acid bacteria, lactose is mostly oxidized to lactic acid. The latter is partially broken down to propionic acid by propionibacteria, which are also present in the mixture. Many other substances form during fermentation that contribute to the unique taste of kefir, such as pyruvic acid, acetoin, and amino acids. Some ethanol and carbon dioxide form during fermentation as well. The milk’s acidity increases and its proteins coagulate, and the milk turns into kefir! Like milk, kefir contains some calcium Ca, B vitamins, and considerable quantities of select other vitamins. We can consider the homemade kefir we obtained not only a great base for smoothies and salad dressing but a fine source of nutrition as well.
Safety precautions: perform the experiment only under adult supervision.
Homemade kefir - choose your method!
Equipment: 3L milk, kefir starter culture, 3 tsp sour cream, 50 mL store-bought kefir, 1L glass bottles, gauze, rubber band, tile, pot.
Pour 3L milk into a pot and bring to a boil. This eliminates unnecessary bacteria. Let cool to room temperature and divide into three clean 1L glass bottles. Add the components that turn milk into kefir: add store-bought starter culture to the first bottle, 3 tsp sour cream to the second bottle, and 50mL store-bought kefir to the third bottle. Mix thoroughly and cover each bottle with gauze. Leave the bottles in a cool, dark place for 12 hours. Your delicious, homemade kefir is ready!
Kefir is a popular fermented milk product obtained via acidic and alcoholic fermentation. It’s usually made by adding a symbiotic culture of milk bacteria and yeast to milk in order to convert lactose, or milk sugar, into lactic acid and complete the fermentation process. Lactose is a disaccharide found in milk consisting of glucose and galactose fragments. Under the influence of lactic acid bacteria, lactose is mostly oxidized to lactic acid. The latter is partially broken down to propionic acid by propionibacteria, which are also present in the mixture. Many other substances form during fermentation that contribute to the unique taste of kefir, such as pyruvic acid, acetoin, and amino acids. Some ethanol and carbon dioxide form during fermentation as well. The milk’s acidity increases and its proteins coagulate, and the milk turns into kefir! Like milk, kefir contains some calcium Ca, B vitamins, and considerable quantities of select other vitamins. We can consider the homemade kefir we obtained not only a great base for smoothies and salad dressing but a fine source of nutrition as well.
Safety precautions: perform the experiment only under adult supervision.










![Chemical printing in 10 minutes
Chemical printing, or your favorite image on a postcard in 10 minutes
Equipment: sodium carbonate, citric acid, ammonium iron(III) sulfate, potassium hexacyanoferrate(III), beaker, cotton roll, watercolor paper, negative image, hair dryer.
Dissolve sodium carbonate, citric acid, ammonium iron(III) sulfate, and potassium hexacyanoferrate(III) in water to create a light-sensitive mixture. Use a cotton roll to apply this solution to a piece of watercolor paper, then cover the paper with a negative image and set the paper and negative under a lamp. After 10 minutes, remove the negative image and rinse the paper with water, then dry it with a hair dryer – you’ve made a cute winter postcard!
Under the influence of bright light, the iron(III) ions in the photosensitive mixture begin to actively enter an excited state. At the same time, they oxidize citric acid ions, resulting in the formation of a complex mixture of organic substances and iron(II) ions, with which potassium hexacyanoferrate(III) forms an insoluble blue compound:
Fe²⁺ + K₃[Fe(CN)₆] → KFe[Fe(CN)₆]↓ + K⁺
This compound is firmly fixed in the pores of the paper, so when rinsed with water, the blue pattern remains!
A similar experiment is included in the “Cyanotype” set from the MEL Chemistry subscription.
Warning: only under adult supervision. Chemical printing in 10 minutes](https://i.ytimg.com/vi/dcfAKVyYhtY/mqdefault.jpg)