You will find that the concentrated juice provided with your kit seems to mix easily with the water that you add but in actuality, the juice will settle to the bottom of the fermenter because it is heavier than the water you add.
This will have the affect of giving you a false initial hydrometer reading. Since wine ingredient kits are pretty much on target with where the hydrometer reading should be, the fact that you get a reading which is out of the suggested range should be a clue to you that something is not right. Stirring the fermenter vigorously will disburse the water and juice concentrate evenly.
Another problem may be when you sprinkle the wine yeast onto the top of the fermenter. There will be a lesser supply of sugar at the top of the fermenter and your yeast may not get off to a quick and healthy start. If the yeast does settle through the thinner layer at the top it may still not be able to ferment properly in the high sugar environment of the unmixed juice concentrate.
Another benefit to aggressive stirring at this early stage is the oxygenation of the wine must. We preach, preach, preach about keeping air away from your wine must to prevent the oxygenation of your wine. That is true when you have wine. But at this moment you have juice, not wine. Yeast loves oxygen. By aggressively stirring the wine must you will provide a good source of oxygen for the yeast and help it get off to a robust start.
Whether you are looking to make your wine from a WinExpert ingredient kit or from a Cellar Craft ingredient kit, from fresh fruit or from one of the BlueStem fruit wine ingredient kits listed on our website at http://www.bluestemwine.com/ we can help you get off to a great start. BlueStem Winery, in addition to carrying a complete line of winemaking supplies, also carries homebrewing equipment, supplies and ingredients for the home brew enthusiast. We offer prompt, courteous and knowledgeable service.