6.2 Thermal Styling: Curling Irons, Pressing Combs & Finger Waving

Key Takeaways

  • Thermal Hairstyling, Curling Iron Techniques, Styling Hair using Pressing Combs, and Finger Waving Techniques are four separate named sub-topics of the 15% Hair Cutting and Hair Styling category.
  • Marcel irons are non-electric or electric irons manipulated by a rotating handle; the barber tests iron temperature on a piece of white tissue paper before it touches hair.
  • Hair pressing is a temporary straightening that breaks hydrogen bonds with heat and pressure and reverts completely with moisture, unlike chemical relaxing which permanently rearranges disulfide bonds.
  • A soft press removes about 50 to 60 percent of the curl in one pass, a medium press about 60 to 75 percent with slightly more pressure, and a hard or double press removes up to 100 percent by passing the comb twice on each side.
  • Finger waving is a wet-set technique that shapes hydrogen bonds using waving lotion, the comb and the fingers, forming ridges and hollows in alternating directions.
Last updated: August 2026

Thermal Styling: Curling Irons, Pressing Combs & Finger Waving

Blueprint anchor: Hair Cutting & Hair Styling (15%) → Curling Iron Techniques; Thermal Hairstyling; Styling Hair using Pressing Combs; Finger Waving Techniques. Four of the twelve sub-topics in the category are gathered here. They share one physical principle: they all manipulate hydrogen bonds, so every result in this section is temporary.


1. Thermal Irons: Construction and Control

PartFunction
Barrel (rod)The heated cylinder the hair wraps around; barrel diameter sets curl size
Groove (shell/clamp)The hinged half that presses the hair against the barrel
HandlesGrip; the barber's thumb rotates the moving handle
SwivelPrevents the cord from twisting during rotation
Guard / restKeeps the hot barrel off the counter

Conventional (marcel) irons are manipulated by rotating the handle so the barrel turns inside the hand. Classically these were non-electric irons heated in a stove; the modern version is electric with the same handle geometry. Electric spring irons hold the clamp closed with a spring and are the common modern styling iron. Flat irons press hair between two heated plates for straightening rather than curling.

The tissue-paper temperature test

Before an iron touches a client's hair, clamp it on a strip of white tissue paper for about five seconds:

Tissue resultMeaning
UnchangedSafe to use
Scorched, browned, or smokingToo hot — cool the iron before proceeding

This test is a fixture of barbering examinations because it is a procedure with an unambiguous answer. Fine, light, lightened, or chemically treated hair requires a lower temperature than coarse, dark, virgin hair.

Iron work rules

  • Insert a hard rubber or heat-resistant comb between the iron and the scalp to shield the skin.
  • Keep the iron moving; a stationary hot barrel scorches.
  • Never use a thermal iron on hair treated with a hydroxide relaxer or on chemically damaged hair without reducing heat — the cortex is already compromised.
  • Never use an iron on wet hair unless it is a tool specifically engineered for wet-to-dry use.
  • Clean carbon and product build-up off the barrel; residue transfers to the next client's hair and to the next client's scalp.

2. Hair Pressing with a Pressing Comb

Hair pressing temporarily straightens overly curly hair with a heated pressing comb (a metal-toothed comb, traditionally brass or stainless steel, heated in a stove or electrically). It is thermal, therefore temporary, and it reverts completely on contact with moisture.

The three degrees of press

PressCurl removedMethod
Soft pressAbout 50–60%One pass of the pressing comb on each side of the section
Medium pressAbout 60–75%One pass on each side with slightly more pressure
Hard press / double pressUp to 100%Two passes of the comb on each side of the section

Exam Key: the discriminator between a soft and a medium press is pressure, not an extra pass. The discriminator for a hard press is the second pass — which is why it is also called a double press.

Procedure

  1. Shampoo and dry thoroughly. Pressing must be done on dry hair.
  2. Analyse scalp and hair: an abraded scalp, contagious disorder, or severely damaged hair contraindicates the service.
  3. Apply pressing oil or cream — it conditions, adds sheen, prevents scorching, and protects against breakage.
  4. Section the head into four quadrants and work in small subsections.
  5. Test the comb's temperature on a piece of white paper or a light cloth before it touches hair.
  6. Press the back of the comb — not the teeth — against the hair while the teeth carry the section. The heat and pressure of the comb's back does the work.
  7. Work from scalp to ends, keeping the comb off the scalp.
  8. Style once fully cooled.

Pressing vs. chemical relaxing

Hair pressingChemical relaxing
Bonds affectedHydrogen (temporary)Disulfide — permanently rearranged (lanthionization with a hydroxide relaxer)
DurationUntil the hair is wetted or exposed to humidityPermanent on the treated hair; new growth requires a retouch
Reverts with water?Yes, completelyNo
Restricted barber may perform?Yes — thermal styling is not a chemical serviceNo — strictly prohibited
Damage modeHeat: dryness, breakage, burnt hairChemical: over-processing, scalp burns, breakage

Scope point for Florida: because pressing is thermal rather than chemical, it sits inside the Restricted Barber scope. A relaxer does not.

Burnt hair, and why it cannot be fixed

Excessive heat on a pressing comb or iron destroys the keratin protein in the cortex. Burnt hair has a distinctive sulfurous odour, turns dull and reddish, and becomes brittle and straight in a way that will not curl again. There is no treatment: burnt hair must be cut off. A client with lightened or previously chemically treated hair carries the highest risk and requires a substantially reduced temperature.


3. Finger Waving

Finger waving is a wet-set technique that shapes hair into alternating ridges and hollows using waving lotion, a comb, and the fingers. It is the classic foundation of thermal and wet-set styling and is on the Florida outline in its own right.

Terms

  • Ridge: the raised wall of hair where two directional movements meet.
  • Hollow (wave trough): the recessed valley between two ridges.
  • Shaping: the directional area in which the wave pattern is formed.
  • Waving lotion: a gel-type liquid that holds the hair in place while it dries. Applied to damp hair, it should be used sparingly — too much causes flaking.

Procedure for a horizontal finger wave

  1. Shampoo, towel-dry to damp, and apply waving lotion evenly through one side at a time so it does not dry before the wave is formed.
  2. Find the natural part and natural growth direction — a finger wave fights a cowlick and loses.
  3. Beginning at the front hairline on the heavy side, place the index finger of the left hand on the head above the intended ridge.
  4. Draw the comb forward about an inch along the finger, then turn the comb teeth downward and direct the hair upward against the finger to form the ridge.
  5. Flatten the comb against the head and comb the hair in the opposite direction to form the hollow below the ridge.
  6. Move down and repeat, forming the next ridge in the opposite direction to the one above it — this alternation is what makes it a wave rather than a series of parallel lines.
  7. Do not force the ridge with the comb teeth; pinching the ridge between two fingers creates a sharp, unnatural crimp instead of a rounded wave.
  8. Dry completely under a hood dryer, then comb through lightly.
        RIDGE ──────╮        ╭────── RIDGE
                     ╲      ╱
        HOLLOW        ╲____╱        HOLLOW

   Each ridge is formed by combing in the OPPOSITE
   direction to the ridge above it. Same direction
   throughout = parallel lines, not a wave.

Exam Key — finger waving is a temporary wet set. Like blow drying and pressing, it works on hydrogen bonds and is undone by water. Nothing in this section alters a disulfide bond, which is precisely why none of it is a chemical service under Florida law.

Test Your Knowledge

Before using a heated thermal iron or pressing comb on a client, the barber should test its temperature. What is the standard test and what result indicates the tool is too hot?

A
B
C
D
Test Your Knowledge

A client requests a hard press. What distinguishes a hard press from a soft press?

A
B
C
D
Test Your Knowledge

Which statement correctly distinguishes hair pressing from chemical hair relaxing?

A
B
C
D
Test Your Knowledge

When forming a horizontal finger wave, what must the barber do at each successive ridge for the result to read as a wave?

A
B
C
D