low SG

Take another reading. That number doesn't make sense.

after secondary fermentation, the wine settled at 0.900 for 2 days, so I stabilised. It stayed at just over 0.900

Look at your hydrometer scale again, I think it says 0.990, not 0.900. Kit instructions often say to stabilized at 0.998 or lower. 0.990 is good for a red kit because it means the wine is fully dry.

Pp

OK OK - I guess it is 0.990, whatever is just above the 1 on the scale. The kit calls for 0.998 - 1.005, so it is still out of the range and tastes very dry.

Should I add sugar and stabilizer just before I bottle??

Regardless of the reading and the kit instructions, if you like it, leave it alone. If it's too dry, sweeten carefully. If you add sugar too quickly, it can cause an eruption like Mount Vesuvius. If you add too much sugar, there's no easy way to make it less sweet. If you do choose to sweeten it, make sure it's stable before you bottle. The best way to do this is to allow it to bulk age for a few months. If there's no sign of life after that, you can safely bottle it.

Greg

The point of checking the SG is to be reasonably certain that fermentation has stopped. If you're below the target SG, and the wine is no longer bubbling, then fermentation is finished, which is good.

At this point (as the instructions should tell you) you should be adding the clarifying agent(s). Most kits also have you add sorbate as a precaution, in case there is any residual sugar. What I don't understand is why you would want to add sugar before you bottle. If this is a dry red kit, why not leave it dry?

If you are going to sweeten it, then you definitely need to add the sorbate, to prevent renewed fermentation. If you are going to leave the wine dry, the sorbate is optional. It shouldn't hurt, but you shouldn't need it, based on your SG readings. In any case, don't be in a rush to bottle it. Particularly if you do sweeten the wine, give it a few days to adjust and settle before bottling.

Doug

What kind of kit are you making? The Anchorage Fishwrapper and Litterbox Liner Press

Michael, I think you are reading your hydrometer wrong to begin with. If this is an inexpensive hydrometer it is graduated in 0.002 S.G. increments. the first line above the 1.000 mark is 1.002, the first below is 0.998 below, meaning toward the bottom or base.

Joe

Michael:

I think youwould benefit the most from visiting your local Home Brew Shop and having somebody explain the hydrometer to you.

Steve