Synthetic wigs are constructed of plastic or plastic-like fibers. When you apply extreme heat to synthetic fibers, they melt or burn. Therefore, you cannot use a flat iron, curling iron, or clothes iron to straighten a curly synthetic wig. In addition, chemical treatments used on curly human hair wigs will damage the synthetic fibers. However, by warming the fibers with hot water and allowing gravity to straighten the synthetic wig for you, you can control the amount of straightening and prevent damage to your wig.
Pin the curly synthetic wig to the Styrofoam wig form. Use pushpins to secure the wig at the front-center, temples and base of the skull. For longer wigs with greater weight, you may want to place more pins throughout the wig.
Comb out the synthetic wig using a wide-toothed comb to remove any tangles.
Place the wig form on a stand that allows the hair to flow unhindered to its full length. For shoulder-length or shorter hairstyles, a 2-liter bottle filled with water is sufficient. For longer styles, use a camera tripod.
Place the wig and stand in the bathtub.
Boil a large pot of water. Use a meat thermometer and hold the water at between 180 to 185 degrees Fahrenheit. Do not boil the water any hotter as it will melt the synthetic fibers.
Pour the water carefully over the wig, starting at the crown. Allow the water to flow down the length of the wig. If the wig is extremely curly, you may have to pour several pots of water to achieve a completely straight wig.
Spray the wig with a detangler made for synthetic hair. Use a wide-toothed comb and carefully work through the wig to lay the hair completely flat.
Allow the wig to air-dry. Depending on the length and thickness of the wig this could take several hours. Do not blow-dry the wig.
Comb the wig again once dry. If the wig is not straightened to your satisfaction, repeat Steps 5 through 8 again.
The more hot water used in Step 6, the straighter the wig will become.
Do not be tempted to pour hotter water for a faster process. Water hotter than 185 degrees Fahrenheit will melt the synthetic fibers. Once straightened, a synthetic wig will not return to its curly state like natural curly hair does.