In methods according to the invention, subsurface formations below the surface of the earth are detected by introducing a condensable material in vapor form into the subsurface formation, measuring radiation of the condensable material, increasing the concentration of the condensable material through condensation, measuring radiation of the condensable material of increased concentration, and comparing the radiation of the condensable material of increased concentration to the radiation of the condensable material in vapor form to identity the presence of the condensable material. In a practical example employing methods according to the invention, gamma radiation in the well is logged to define a background radiation response, the well is chilled by pumping cool water into it to cause steam surrounding the well to form condensate, gamma radiation in the well is logged to define a new radiation response, and the new radiation response is compared to the background radiation response to identity vapors where the radiation increased.