Thermage was based upon the observation by a surgeon that when skin was cut using heat (a process called diathermy) the skin retracted significantly. From this observation, experiments showed that if skin could be heated in a controlled fashion, the protein called collagen would contract causing a tightening effect without damaging the cells and causing burns.

The Thermage machine uses radio frequency electric current to produce this effect. A large pad is placed on the small of the back, the buttock or the thigh. This is called the return electrode and is where the radio frequency current exits the body.

The Thermage hand piece has a very complex tip. The basic tip is 1.5 cm by 1.5 cm. When the machine is on, the tip can be placed against the skin. Radio frequency current passes from the tip to the return pad and back again. Due to the different sizes of the tip and the pad, heat is generated in the tissue directly under the tip. This heat causes collagen to contract and a tightening of the skin to occur.

However, to allow more heat to be generated in the skin, the tip undergoes cooling almost immediately. Therefore by holding the tip against the skin for the whole treatment cycle, the skin and tissue beneath it is heated, causing the required contraction and tightening - and then cooling straight away reduces any pain in the skin due to the heat.

Therefore in one cycle, one square of skin measuring 1.5 cm by 1.5 cm is treated. To get the required effect over a large area of skin, such as the face, neck or abdomen, it is essential that the whole skin area is treated. In order to do this precisely, a transfer is placed upon the skin with a grid of squares all 1.5 cm by 1.5 cm. In this way, the Thermage operator is able to make sure each square is treated satisfactorily and then each overlapping area is also treated.

By following a set routine, a skilled Thermage operator is able to get adequate contraction or tightening of the whole of the treated area and then, by choosing certain areas to treat again, extra support can be given to get a better result.