Those who grow grapes in their yard often start making homemade wine in the fall. Unfortunately, many face disappointment along the way—the drink’s low alcohol content makes it more like grape juice than wine.

The reason for this mistake is the low sugar content in the grapes, which leads to poor fermentation.

The amount of sugar in the berries affects both the density of the must and the quality of the wine. The longer the grapes stay in the sun, the more sugar they contain. If the berries are devoid of sugar, add regular sugar to the must. Unfortunately, you can’t determine the sugar content in the grapes by eye or by checking the weather forecast. Not everyone has access to specialized tools, but there is a simple way to determine whether you need to add more sweetness or if they must already contain enough sugar.

Once the berries have started fermenting, which takes about a day, it’s time to determine the sugar content. Just add a raw chicken egg to the must.

If the egg rises to about 2 cm above the liquid’s surface or a little more, the alcohol content is around 11-13%, which is ideal for wine. If the egg sinks or barely rises above the surface, try adding some sugar and check again in a day.