Has anyone got any recommendations on how to clean up old materials?

I’m building an application where by meshes are loaded dynamically based on a users selection.

Materials are built and applied within the application using a bunch of ColorMaterials and Environmentmaps.

when i load another mesh, materials are loaded again and go into the Material Library.

This ends up blowing out the size of the material library fairly quickly, and i get an error after a while about resources running out.

I’ve tried a few things to try and remove old materials, but it seems to break things when i do.

not sure if theres anything i’m missing?