Note: All acid waves have three components: a waving solution, an activator, and a
neutralizer. The activator contains the agent Glyceryl Monothioglycolate (GMTG) and should be considered carefully before deciding to
use an Acid Wave since repeated exposure to GMTG is known to cause allergic sensitivity in both stylists and clients.
An exothermic wave is called thus because of the chemical reactions involved in the waving
process. An exothermic chemical reaction produces heat, and an Exothermic Wave uses exothermic chemical reactions to produce heat as a
way to speed up the processing time of the permanent wave. Exothermic waves have three components (like acid waves): waving solution,
activator and neutralizer. The waving solution contains thio just as in a cold wave and the activator contains an oxidizing agent
(usually hydrogen peroxide). Combining the two creates a rapid release of heat and an increase in the temperature of the solution.
The increased temperature increases the rate of the chemical reactions in the hair and shortens the required time to process the curl.
Exothermic waves are good for coarse, thick and/or resistant hair types, typically process
faster than alkaline waves and create firm, strong curls. However, like an alkaline perm, exothermic waves can damage delicate hair
and often has a strong, unpleasant ammonia odor.
An Endothermic Wave is the counter-point to the Exothermic wave. Where the exothermic wave
generates its own heat using a specific type of chemical reaction, the Endothermic Wave utilizes reactions that absorb the heat from
its surroundings. This means that they are only activated by an outside heat source – typically a conventional hooded hair dryer.
As is obvious, most True-Acid waves are endothermic, but not all endothermic waves are “true” acid waves.
Ammonia-Free waves use an ingredient that does not evaporate as readily as ammonia, so there
is very little odor associated with their use. One common substitute for ammonia is an alkanolamine, such as aminomethylpropanol and
monoethanolamine. These ammonia-free waves generally process the same as standard alkaline waves but since the substitutes for the
ammonia don’t evaporate as readily as ammonia, there is typically very little odor associated with their use.
Ammonia-free waves are generally suited to use on hair that is porous to normal in resistance
level, processes at room temperature, and typically generates medium to fine curls. While these waves may not smell as strongly as
ammonia, they can still be every bit as alkaline and just as damaging. Remember that ammonia-free doesn’t mean damage-free.
Thio-Free Waves use a substitute for Ammonium Thioglycolate (ATG) as the primary reducing
agent in the waving formula. Commonly, the substitutes used are cysteamine or mercaptamine which while not technically being ATG are
still thio compounds. Thio-Free Waves are marketed as being damage-free, but this isn’t necessarily true. In high concentrations these
can be as damaging as thio to the hair.
Thio-Free Waves have the benefits of processing at room temperature, and produce medium to
fine curls. The Thio-Free Wave is suited for use on normal to porous hair types, and can be gentler on the hair depending on the
individual formula used. Since the strength varies from manufacturer to manufacturer be sure to use caution in selecting and using a new formula.
Low-pH waves use an alternative formula for their waving solutions. Instead of Ammonium
Thioglycolate, low-pH waves use sulfates, sulfites and bisulfites as their primary ingredients. These formulations are very gentle
since they work at a low pH, but while they have been in use for years, they are not very popular. The trouble is that the permanent
waves based on sulfites are very weak and do not provide firm curls. Because of this they are often marketed for use in body wave services.
The weak formulation of Low-pH waves make them suited for use with fine and damaged hair or
in cases where a gentle wave is desired as opposed to firm curl. Low-pH waves are endothermic waves and will need the heat of a hair dryer.
So, as you see, there are many options available when you start looking for a permanent wave
formula. Knowing what the different terms mean and how they differ can help you select the right option for your hair, and help you
know whether this is going to be something you can manage on your own. Just remember that if you are unsure, always ask a professional
for guidance, or at the very least try to err on the side of caution.