You can easily calculate the strength of your wash, if you know your
starting & final specific gravities (SG) - measure these with a hydrometer.
The % alcohol is (Starting - Final) x 129. eg: if your sugar/water mix of
SG=1.120 drops to 0.980, then you have a wash with (1.120-0.980)x129=18.1%.
Some winemakers use the Ebulliometer degree table for their wines - it estimates the difference between the boiling point of their wine & distilled water (eg if your distilled water boils at 100C, and the wine boils at 93C, then it has 8.8% alcohol). I've created the following calc based on data from Churchward (ACI Jnrl & Proc, Jan 1940), supplied by Duncan. Note that some correction may required if there is still residual sugar present. This calc is only good for % alcohol less than 25%.