A modification of the fine grain TL dating technique for measuring the natural dose is presented. In this technique (foil technique) we tried to make very thin samples and with the necessary plasticity, in order to achieve the best heating contact between sample and heater plate. Because the so prepared samples have not the same amount of powder a suitable new normalization technique is also proposed. The advantages of the proposed foil technique are such that make it quite suitable for samples with low levels of natural TL and also for authenticity testing. This technique was tested using artificially irradiated samples with known doses and applied to the dating of a mortar containing ceramic grains.