I liked Allen's math, but I think it's a little complex:
If you want C oz. of high gluten flour, you know
> X + Y = C
> 0.14 = (0.125*X + Y)/(X + Y)
>
> We have two equations and two unknowns so we can solve for X and Y to get
>
> X = C * 0.86/0.875
> Y = C - X
If you assume that the amount of gluten to be added won't be significant
compared to the amount of flour, then:
X + Y = X (close enough)
Y = X * (0.14 - 0.125)
Y = 0.015X
Using volume measures, a Cup is 250ml and a tbsp is 15ml. There are 16.666
tbsp in a cup. Then you need to add 1/4 tbsp of gluten for each cup of
flour. The fact that it is so small, bears out my original assumption.
Dave Barrett