Cotton is one of the most common fabrics and requires at least 400 degrees Fahrenheit. Meanwhile silk and polyester require less heat at 300 F. The dots on a fabric label or an iron indicate the heat level. One dot is low heat, two is medium heat, and three is high heat. Steam is the highest heat level and can make ironing faster, requiring less effort when passing the iron over the fabric. When using steam or spraying water on the material, the water helps transfer the heat evenly on the surface. While all irons differ slightly in heat output, use the following basic guidelines for the proper temperatures to iron different fabric types. The settings use a scale of 1 to 7; 1 is the coolest and lowest, usually called the nylon setting, while 7 is the hottest and highest, commonly called the linen setting. 

If your iron uses a different scale or you want to know more exact temperatures for ironing different types of fabric, follow these guidelines for degrees Celsius and Fahrenheit: If you must switch back to a lower iron temperature, give your iron at least five minutes to cool down before you use it again. When in doubt about what temperature to use, start low and iron on the wrong side of the fabric with a pressing cloth. You can always move the temperature up gradually to remove tougher wrinkles and still prevent scorching. Scorch marks can be difficult to remove but not always impossible if caught early and treated while they are light in color.