Hi: I have made a font with two masters, and a Bold Instances. But the Bold is too thin in the horizontal stems. The vertical are correct. How can I change the weight specific in the horizontal part? Thank you.
The instance is a mathematical interpolation (or extrapolation) of the positions of nodes in your masters. I don’t think you can just adjust one dimension via interpolation settings (and with most or all designs it wouldn’t work well anyway).
This would be easier to advise on if you showed what your masters and instances look like.
RMX Scaler is probably best for what you want to do. If it is just a tiny bit too thin, you may also be able to get away with Filter > Offset Curve and only apply vertical offset. No matter how you do it, I expect that you will have to step through the results anyway and nudge a point here and there.
Do you mean that the Bold is an interpolation between a light and a Black? Then you can try the
InterpolationWeightY parameter. But that tends to disturb the diagonals.
If it is only a problem in a few glyphs, then correct them with brace layers. If it is a global problem, you might need to add another master and correct it with the tools Rainer described above.