Much of his work is figural, reflecting an interest in the human face and form, and is primarily in steel, which he describes as giving a scale and "whoom-factor" not possible with other media.
[3] During his time as a teacher Kirby's own artistic sense bent towards sculpture, and after sixteen years he quit teaching to focus on his work.
"[5] Kirby's oeuvre is largely figural,[2] reflecting a fascination with the human face and form that has persisted since his time working in stone.
[3] Though he uses an industrial medium in steel, Kirby's pieces are intended to express elegance and grace, and guardianship; a reviewer of one of his exhibitions noted that "they do not dominate their settings, but instead calmly watch over their environment with an air of gentle theatricality.
[10] When unveiling When the Sky's the Limit the Spirits Soar in 2005, Prince Edward remarked that "I don't know quite what the word is.