Reducing masters: 3 to 2 masters migration

Hi there!
I made Alegreya Sans in Glyphs 1 using 3 masters: 100, 400, 900
Now I am starting to expand the character set and I am wondering how can I reduce it to two masters and add brace layers only in the glyphs that actually have changes in its outlines.

Do you have any idea of what kind of approach is a good strategy? or how can I automate the process? I thought this:

  1. Generate instance of the regular weight: the original master (A)

  2. Delete the regular master

  3. Generate instance of the regular weight: the interpolated master (B)

  4. Make a new glyph file with two masters: A and B

  5. Generate an instance © extrapolating those masters, in order to amplify its differences

  6. Compare C and A using @guidoferreyra Show Next Font plugin

  7. Find which glyphs have different contours and add brace layers in the original file.


I did a simple DrawBot script a while back to help me spot inconsistencies in masters. It takes a list of fonts and draws a grid of glyphs with all fonts ontop of each other.

You could use that to compare two fonts, one interpolated and one created from the middle master. It’s pretty much the process you just suggested but maybe this would get you a better overview.

You don’t have to create different Glyphs files. You can use the Disable Masters parameter.

And I used to overlay two textboxes in InDesign with two bright but complimentary, semi-transparent, multiplying colours (like bright blue und orange). So that where they overlapped, they would become pretty dark and the non-overlapping parts would have a flashy color:

I added a new script: Master to brace layer to our repo:


1 Like