Homemade wine needs to be filtered after primary fermentation.

Filtering is to prevent the wine from over-fermentation, which produces fruit vinegar. If you don't filter, you can't make wine and it is more likely to spoil. Also, the lighter color of the wine may be related to the grape variety and has little to do with filtration.

The primary fermentation is followed by a secondary fermentation.

The second fermentation lasts 1-3 days and takes place at the same temperature as the primary fermentation, but it is necessary to fill the container to the top and to wrap the bottle with plastic wrap and pierce the wrap with a needle.

The secondary fermentation is a step that improves the quality of the wine and further settles the pomace, and can be omitted if conditions are not favorable.

Extended information:

Primary Fermentation Stage

The main fermentation stage begins 24 to 48 hours after tanking, after which a large number of bubbles rise to the surface and the pomace also rises to form a hard pomace cap. Because the fermentation process also needs a small amount of oxygen and produces more carbon dioxide gas, so do not seal, to leave ventilation holes, in order not to fall into the dust and small insects as the standard can be.

Temperature - during the main fermentation barrel temperature control between 15-30 degrees, barrel temperature to the bottom of the pomace cap temperature shall prevail; low temperature fermentation time is extended, out of the color of the wine is lighter, but the taste and quality of better. Higher temperatures shorten the time, the color of the wine is better, but the taste and quality is not as good as low-temperature fermentation.

Frequency of cap pressing - cap pressing, i.e., a thick layer of hard cap formed by the floating pomace is pressed into the wine, which can prevent the pomace from breeding bacteria, and enhance the infiltration of the fruit skin, generally 2-4 times a day;

Fermentation time - the main fermentation generally lasts 7-4 times a day. -The main fermentation generally lasts 7-10 days, the specific time is determined by the grape variety, the amount of sugar added and fermentation temperature. To determine the separation time. Separation and filtration criteria are: after a fermentation period (a large number of bubbles produced) after the amount of bubbles greatly reduced or disappeared, can smell a very strong wine flavor and taste the sweetness disappeared when it can be filtered. It is best not to leave the wine unfiltered for a long period of time, because too much time will increase the tannins and other substances in the skins that affect the taste and make the wine more astringent.

Separation of the wine - after the main fermentation, it is necessary to separate the wine by filtration. It is best to stop stirring or pressing the cap for 12 hours before separation, so that the wine is not so cloudy, and it is best to separate the wine by siphoning with a siphon tube, which prevents the wine from becoming cloudy and coming into contact with the air, resulting in oxidation or acetic acid bacterial infections. This prevents the wine from becoming cloudy and from being exposed to too much air, which may cause oxidation or acetic acid bacterial infection. After the separation of the liquor, the dregs can be filtered through 3-5 layers of gauze or nylon socks, gently squeezed by hand, and the pressed wine can be poured into the siphoned liquor for secondary fermentation.

Baidu Encyclopedia - Homebrewing Wine