We present a model of He-3 relaxation on the surface of borosilicate glass which accurately predicts observed relaxation rates and their temperature dependence. Above room temperature He-3 dissolves into Pyrex, where interactions with Fe3+ ions result in a relaxation time of approximate to1 ms. Gas exchange across the glass surface of an enclosed vessel leads to T-1(-1) = A/V (3.9+/-1.4) x 10(-2) cm/h at room temperature, where A/V is the surface-to-volume ratio. The activation energy for relaxation is 13.7+/-0.7 kJ/mol and is dominated by the activation energy Of He-3 diffusion in glass. This is the first successful confirmation of predicted He-3 relaxation rates in glass vessels. (C) 2003 Elsevier Science B.V. All rights reserved.