Physics and Chemistry

Electrolysis only becomes intelligible when the word is broken apart. The field uses one insertion craft and three destruction logics. Direct current creates chemistry. High-frequency alternating current creates heat. Running both together creates chemistry on a warm substrate and therefore changes the kinetics of both. Nearly every argument about "which modality is better" is really an argument about which damage regime better fits a given follicle shape, depth, hydration state, and operator skill level. Sources: Wagner et al. 1985, PMID 3989007, Richards & Meharg 1995, PMID 7673501. Confidence: C2.

On the galvanic side, the governing principle is Faraday's law: the amount of electrochemical change is proportional to total charge delivered. The probe acts as a cathode in the follicle while the client completes the circuit through the indifferent electrode. In saline tissue, sodium and chloride are already dissociated, and water is the relevant reducible species at the cathode. The practical cathodic half-reaction is 2H2O + 2e- -> H2 + 2OH-. Sodium does not plate out in aqueous tissue; instead, the newly generated hydroxide ions associate with sodium ions already present in the extracellular fluid, yielding the lye-equivalent the trade describes as sodium hydroxide. That point matters because trade shorthand often writes a global NaCl-plus-water equation and leaves the impression that metallic sodium is somehow being generated inside tissue. It is not. The tissue event that matters is hydroxide accumulation at the negative pole plus hydrogen gas formation. Sources: Wagner et al. 1985, PMID 3989007, AEA curriculum overview. Confidence: C1-C2.

The arithmetic is straightforward once written cleanly. A current of 0.3 mA delivered for 30 s equals 0.0003 A x 30 s = 0.009 C. Dividing by Faraday's constant (96485 C/mol) gives about 9.33e-8 mol of electrons. Because the cathodic half-reaction produces one hydroxide ion per electron, the same treatment yields about 9.33e-8 mol of hydroxide, or 0.093 micromole. Expressed as a sodium-hydroxide equivalent, that is roughly 0.0037 mg. Those numbers look trivial in macroscopic chemistry, but a follicle is not a beaker. The reactive volume is tiny, diffusion is constrained, and the destructive target is microscopic. That is why small milliampere-second products can still matter biologically. The old trade language of "units of lye" is a convenience layer laid on top of the same reality. Dectro's own comparison material still includes a key for calculating U.L., which is the machine-interface remnant of this older electrochemical bookkeeping. Sources: Dectro cross-reference chart. Confidence: C1 for the calculation, C2 for the machine-market interpretation.

Because galvanic injury is chemical, time is not just an inconvenience; it is part of the dose. The hydroxide has to be generated and allowed to diffuse into the vulnerable structures of the lower follicle. If the operator cuts dwell time too aggressively, the treatment may produce a hair that feels loosened but does not receive enough chemical damage at the dermal papilla and bulge to remain dead. This is why practitioners who favor galvanic tend to sound conservative about timing. They are not just clinging to an old method; they are respecting the kinetics of a slow reaction. It is also why galvanic is relatively forgiving of slight angle or depth imprecision compared with flash thermolysis. Hydroxide can diffuse around a little. A thermolysis pulse cannot diffuse backward in time if the probe tip is sitting in the wrong place. Confidence: C3, because this is a mechanistic inference synthesized from electrochemistry and practitioner literature rather than a modern controlled trial.

Thermolysis is different in kind. The relevant device family is the high-frequency needle-type epilator, and the classic public frequency in the field is 13.56 MHz, one of the internationally recognized ISM frequencies. Dectro's more recent Apilus line made a major branding point of moving to 27.12 MHz, another ISM frequency, with the claim that higher frequency allowed more intense and localized energy delivery in shorter pulses. The regulatory and industrial fact here is stable: electrology sits on the same ISM-band logic that broader RF heating technologies use, which is why the field historically borrowed terms like short-wave and diathermy. The tissue fact is that alternating current passing through moist tissue generates heat in a sharply bounded volume around the active part of the probe. Sources: Canadian ISM band summary, 47 CFR Part 18, ISM frequencies, Dectro Apilus page, Dectro xCell page. Confidence: C1.

Practitioners and manufacturers often describe thermolysis as "water molecule oscillation" or "dielectric heating." That description is directionally fine but incomplete. Follicular tissue is conductive, heterogeneous, hydrated tissue, not a pure dielectric block. What matters clinically is resistive RF heating in a small treated volume shaped by probe geometry, local impedance, insulation, and pulse width. The classic histologic description is a pear or teardrop lesion. Kobayashi's insulated-needle paper and Dectro's later 27 MHz histology study both reinforce the same qualitative point: when current is better confined toward the distal active tip, injury localizes more cleanly to the target region and the skin surface is spared. Sources: Kobayashi 1985, PMID 4044984, Dectro 27 MHz histology study PDF. Confidence: C2-C3.

The temperature target in thermolysis is not arbitrary. Protein denaturation does not happen at a single magic threshold, but the field's practical coagulation target sits around the upper-40s Celsius because the probability of irreversible thermal injury rises steeply there when exposure lasts long enough. This is where the thermal-relaxation-time and thermal-damage-time concepts migrate from broader laser science into electrology. A tiny follicular target can be injured by a short high-intensity pulse if the heat is concentrated before it diffuses away, or by a longer lower-intensity pulse if the tissue is held hot for long enough. That is why old manual thermolysis, flash, microflash, picoflash, and multiplex are not merely marketing names for "stronger" or "weaker" settings. They are different ways of solving the same thermal-dose equation. Sources: Anderson/Parrish selective photothermolysis background, summarized in later diode heat-distribution paper, Dectro xCell mode descriptions. Confidence: C2.

Thermal relaxation time matters because a follicle is not a point target. The lower follicle, bulb, and bulge occupy a vertically distributed structure with different hydration, vascularity, and conductive surroundings. Very short pulses tend to create more abrupt focal injury. Longer pulses allow heat to spread more broadly, which can either help with difficult hairs or harm surrounding tissue depending on where the probe is sitting. This is why modern Apilus marketing distinguishes PicoFlash from MeloFlash and MultiPlex. The machine is really offering different injury geometries: a pinpoint ultrafast insult for clean insertions, or a more spread-out warming pattern for deep, strong, or dehydrated follicles. Sources: Dectro xCell page. Confidence: C2-C3.

Blend exploits the fact that chemistry accelerates on a warm substrate. The Arrhenius shorthand often repeated in the trade is that reaction rate roughly doubles for each 10 °C rise over many biologic and chemical processes. That should not be treated as an exact tissue constant, but it is a good conceptual map. Warm the follicle with RF, and the galvanic hydroxide generation-and-diffusion process becomes more effective in a shorter total dwell. Hinkel and St. Pierre's key insight was not simply that two currents could be applied simultaneously, but that the combination changed the kinetics enough to make galvanic-style destruction clinically practical at a speed practitioners could accept. The reason blend remains attractive for coarse, curly, deep, or distorted follicles is therefore physical, not nostalgic. It widens the destructive envelope in a structure where exact geometry is often hard to predict from the surface. Sources: Zap Hair history of blend, Richards & Meharg 1995, PMID 7673501, Instantronics Elite Spectrum feature list, Dectro xCell blend-mode descriptions. Confidence: C2-C3.

This is also where Altshuler's thermal-damage-time concept transfers most usefully into electrology. A follicle does not care whether the clinician arrives at irreversible injury through laser-mediated optical heating or RF-mediated probe heating; it cares about the time-temperature history experienced by its critical structures. The practical consequence is that electrology settings cannot be compared on wattage or intensity alone. A short hot pulse, a slightly longer lower pulse, and a blend pulse with modest galvanic support may all reach destructive territory by different routes. Practitioners who understand this think in patterns of tissue effect rather than in abstract machine numbers. That is why the better machine interfaces try to translate raw output into area, hair size, probe size, and moisture presets. Confidence: C3, because this is an informed transfer from thermal science to electrology rather than a directly proved electrology theorem.

Current density and tissue impedance determine how cleanly any of these theoretical doses land. The same current spread over a larger active area yields lower current density. A thicker probe or a larger exposed tip can therefore reduce peak density and often reduce pain or overtreatment, but only if the follicle can physically accommodate the probe. Tissue impedance varies with hydration, body site, stratum-corneum thickness, inflammation, and operator contact quality. Dectro explicitly markets automatic moisture-based current adjustment in the xCell line, which is a vendor-specific way of acknowledging that fixed numbers behave differently in dry upper lip skin than in a moister beard or axillary follicle. In galvanic work, high impedance can reduce effective current flow and slow hydroxide generation. In thermolysis, impedance and geometry alter where the heating concentrates. Sources: Dectro xCell page, moisture test and automatic adjustment, Instantronics Elite Spectrum page, skin-sensor circuitry. Confidence: C2.

Insulation is therefore not a minor accessory issue but a field-shaping piece of physics. By coating most of the probe shaft and leaving only the distal segment conductive, insulated probes confine current density and RF heating toward the lower follicle. That reduces unintended epidermal and upper-isthmus exposure and is one reason insulated probes became especially influential in thermolysis and advanced blend work. Kobayashi's paper on insulated needles was early clinical support for this idea, and current product literature from Dectro, Sterex, Ballet distributors, and other suppliers still frames insulation as the right choice for flash or high-heat work in sensitive areas. Sources: Kobayashi 1985, PMID 4044984, Dectro probe chart, Sterex insulated probe description, Ballet probe catalog page. Confidence: C2.

Taken together, the chemistry and the heat explain the clinical personality of each modality. Galvanic pain tends to feel dull and cumulative because the dose is slower and chemical. Thermolysis pain tends to feel sharp and fleeting because the dose is rapid and thermal. Blend hurts in the mixed way that its mechanism predicts. Galvanic is slow but chemically forgiving. Thermolysis is fast but geometrically unforgiving. Blend broadens the target envelope at the cost of more parameter juggling. None of those are mystical truths about "old" and "new" methods. They are what the underlying physics would lead one to expect.