No hair dryer

Sometimes parents want a freshly applied cast to dry faster. And they reach for a hair dryer. This is not a good idea… Why?

A BIT ABOUT PLASTER CAST…

The plaster used in the Ponseti method is so-called plaster of Paris—the English name for calcium sulfate hemihydrate (CaSO₄ · ½H₂O). It sets and hardens very quickly, which significantly shortens the casting process. This type of plaster is produced by partially dehydrating natural gypsum (calcium sulfate dihydrate, CaSO₄ · 2H₂O) at a temperature of about 120–180°C.

FUN FACT

Did you know that plaster of Paris is simply… decorative (modeling) plaster? Since the Middle Ages, gypsum (calcium sulfate) was mined beneath Montmartre. After being calcined and ground, it produced a very pure, fine powder that became a standard material in construction, sculpture, and later in medicine (plaster casts).

When plaster of Paris is mixed with water, a hydration reaction occurs, during which the material hardens—but heat is also released in the process. This means the reaction is exothermic. The more water used and the faster the reaction proceeds, the higher the temperature can become.

That is why a cast must not be additionally “warmed up” with a hair dryer (even on a lower airflow or cooler setting), because plaster itself already generates heat.

Plaster of Paris + water = chemical reaction + heat + hardening,
so this is not simple drying, but a chemical process that must not be accelerated with heat.

WHY DOES THIS MATTER IN CASTING INFANTS?

• An infant’s skin is thin and extremely sensitive—it is easily irritated and prone to overheating and burns.
• Excess heat = a real risk of chemical–thermal burns.
• Too rapid setting = poorer cast quality and a higher risk of errors in correction.

THEREFORE…

The risk of burns is real
Even lukewarm air from a hair dryer can reach temperatures under the cast that may lead to:

• burns
• blisters
• skin necrosis (especially in infants).

Weakening of the cast structure
Overly rapid and uneven drying can cause:

• microcracks
• reduced strength
• poorer maintenance of foot correction.

Uneven drying
A hair dryer heats only the outer layer. Inside, the cast may remain damp, which promotes:

• skin chafing and rashes
• skin maceration
• unpleasant odor.

Particular risk in the Ponseti method
In the treatment of clubfoot, precision is crucial. Any:

• weakening of the cast
• even minimal shifting
  can affect the effectiveness of correction.

HOW TO DRY A CAST PROPERLY?

• Allow the cast to dry naturally at room temperature—deeper layers will dry gradually, releasing moisture outward.
• Protect the cast from moisture for the first 24 hours.

This is one of those “small rules” that have a huge impact on safety and treatment outcomes.