Abstract: The inventive method comprises compressing roughly half a bun of polyimide foam at a rate of no more than 12 feet per minute from its initial height of approximately 15″, until it reaches a compressed height of no more than 2″. The compression is maintained on the bun for no more than one minute, and then released. The half-bun is then permitted to expand, and it will rebound to approximately 90-95% of its initial height. This conditioned foam may then be cut or otherwise formed into acoustical panels of varying heights and/or configurations, without worry about the ultimate shrinkage after treatment. In addition the treated half-bun may be cut into irregular shapes of more varying dimensions, up to the maximum dimension of the treated half-bun.