Unseen Barbara Hepworth letters reveal ‘recipes’ for sculptures – and her high standards

A cache of notes that will be auctioned this week include the artist's instructions to her bronze foundry and show how deeply involved she was with the casting process

Barbara Hepworth's stone and bronze sculptures are recognised around the world for their distinct, curved forms. The oval alabasters and gleaming bronzes, punctured with holes and lozenge-like gaps, were all made in contrasting tones and surfaces, creating a new aesthetic.

Now, Hepworth's unseen letters to the London foundry owner who made many of her bronze pieces offer a revelatory new guide to her work. The bundle of letters and draft sketches, which cover a decade of work and will be sold for the first time this week, also reveal the exacting standards of this pioneering woman, hailed as one of Britain's most important artists.