Electrolysis is essentially electrolysis of an NaCl aqueous solution with the needle acting as the cathode and surrounding tissue as the anode.
1. 2 H2O + 2e- —> 2 OH- + H2 (reduction)
2. 2 Cl- —> Cl2 + 2e- (oxidation)
Na+ appears to be a spectator ion in these reactions.
3. 2 H2O + 2 Cl- —> 2 OH- + H2 gas and Cl2 gas
4. 2 H2O —> 4H+ + 4e- +O2 (a competeting oxidation reaction)
So, how does this correspond to the physical set-up that we see in the office of an electrologist?
For the galvanic electrolysis case, the needle is negatively charged; that is where reduction occurs (also called the cathode in electrolysis). The probe (usually placed in the clients’ hand) is positively charged; this is where oxidation occurs. The clients body acts as a “salt bridge” allowing charge to balance between the two electrodes. Oxidation and reduction occur at the conductors junction with the human body (a rather poor conductor) when current flows through the circuit. When current is flowing through the circuit, we essentially have a cathode in a salt solution (the needle in the pore of the skin being treated) and an anode in a salt solution (the metal “probe” in the hand of the client). At the needle surface, hydrogen gas will be formed along with lye. The lye is what disables the hair growth. At the metal probe in the hand of the client, chlorine gas is formed (probably along with some oxygen gas–it actually has a lower standard electrode potential for forming than chlorine, but concentration effects keep it from dominating the reaction.) In the reference below, it is claimed that HCl forms at the positive electrode. Although this appears to contradict the balanced equation (3) above, it is possible for small amounts of HCl to form there, as shown in equation 4. This is due to the fact that concentration polarization occurs in this type of physical set-up.
Thermolysis utilizes high frequency radiation to essentially heat the tissue around the needle. Very little or no electrolysis occurs when hf is applied to the pore of the skin. Since none of the current being used for hf is going towards chemical electrolysis, it is entirely used for resistive heating. The shape of the needle, intensity and frequency of hf radiation, conduction profile of the skin, and needle penetration depth are some of the factors which affect the heating profile of the radiation. It turns out that the heating profile is concentrated below the epidermis, a desireable outcome. If the needle was heated by conduction, the heating profile would be concentrated at the skin surface, being the least effective at destroying the cells at the root of the hair follicle.
Blend is just a combination of both galvanc and thermolysis, taking the best of both methods for ending hair growth.
A book that I read about this has some useful information about electrolysis. I do not agree with all of the statements about chemistry that I came across in this book. Nonetheless, it has plenty to offer about hair growth stages and all the physiological aspects of hair growth and removal.
Hinkel, A. R. and Lind, R. W., Electolysis, Thermolysis and the blend: The Principals and Practices of Permanent Hair Removal , California, Arroway Pub., 1968.
It is a little old, but the basics have not changed.