Adding a master

Adding a master is an important step towards a successful interpolation. There are several ways to do this:

  • Drag a UFO from the Finder into the font list pane.
  • Click the toolbar Add Master button and select a UFO with the file dialog.
  • You can rearrange the list items by dragging them.

Removing, disabling a master

  • Select a master in the list, hit delete, confirm. This will remove the master from the designspace. Note: there is no undo.
  • To disable a master, hit command U. It remains in the list and part of the document, but it plays no role in the calculations. This is useful if you want to temporarily disable a font.

Updating a master

Superpolator checks for changes made to the master UFOs. So you can edit a master in RoboFont (for instance), then switch to Superpolator and see your changes take effect.


Control click on the master for its menu. If you want to replace a UFO for another, or if the UFO is missing, use the “Select new UFO for this master”. Open in Editor goes to RoboFont for the time being, but this will be an app pref. I think you can guess what Show in Finder does.

Editing the master’s settings


Double click on the new entry to edit various settings and its designspace location. The popover also offers control over what data is included in the interpolation calculations. For instance, this allows a master to contribute glyphs, but not kerning.

  • Contributes glyphs: check to include all glyph geometry.
  • Contributes kerning: check to inlclude the kerning of this UFO.
  • Contributes font info: check to include the font info of this UFO

The masters also contain data that can not participate in an interpolation, but is still vital to the proper functioning of the instances. For instance the feature text or the various groups. The following checks let you set this master as the source. Instances will then copy from this master. Only one master can be a source for something: if you select one master as the source for the features, the other masters have this unchecked.

  • Source for font features: copy the features from this master to all instances.
  • Source for font groups: copy the groups from this master to all instances.
  • Source for font lib: copy the contents of this master’s lib to all instances.


This a field for a short note about this master (or instance). Pro-tip: you can sort on the contents of this field.


Click on one of the axes to get a slider. Click on the gear for a small menu for some often used values. Masters can’t be anisotropic. If you don’t have any axes yet, define some in the Axes panel.