Short brewing a red wine kit

[Bill W]

With the festive season looming, and having no reds in stock, I'm about to kick off a cheapo Rioja style red wine kit. It is the Chateau Vadeau one from Amazon. I'm finding it hard to believe that a tiny 1.3kg container of grape concentrate could make 21 litres (30 bottles) of red wine with acceptable levels of flavour and body, so I'm considering brewing it short to, say, 17.5 litres (25 bottles), which is 5/6ths or 83.3% of its intended volume.
I'm working on the assumption that I will need to reduce the added sugar accordingly, to get the correct O.G. for the revised volume of liquid. As there will be the same amount of sugar in the concentrate, the added sugar will need to be reduced by a little more than 1/6th. I will take an O.G. to check. The kit doesn't quote an O.G. or F.G. so I'll have to do a bit of research on that, unless anyone here can advise.
There are some sachets of finings in the kit. I don't imagine the reduced volume will make any difference when adding finings so I'll just use them as directed.

 

[johncrobinson]

If your kit states what the expected final ABV is for the 21ltrs you could bactrack that way.
But I think the way you intend to do it will be fine also
Its not very critical,Even a 500gram error would not cause any real problems.
Also using all of the finings will be just fine,

Your right, That grape juice must be AWFULLY highly concentrated.

 

[Bill W]

Thanks John, you've confirmed my suppositions and I can press ahead. I'm not expecting a top-notch "keeper", just something fit for purpose.
I'll go for 17.5 litres and reduce the sugar from 4 kilos to 3.5. The ABV will be marginally higher at that but not enough to affect the extra body.
Time to break out the sanitiser and bang the kettle on!