Things You'll Need
Iron-on transfers allow you to customize an item inexpensively, armed only with standard household supplies and equipment. Though T-shirts are the standard fabric for iron-on transfers, you can apply them to virtually any heat-safe cloth surface, including baseball caps. Caps may seem impossible because of their rounded shape, especially if you want to cover the entire hat. However, with a little creativity and patience, that end is undoubtedly attainable.
Set out the ironing board and iron.Turn on the iron so it can preheat.
Acquire or produce enough transfer material to cover the entire hat. Two fully printed 8-by-10 sheets should be enough.
Measure each section of the hat with a tape measure. The hat is a series of triangles sewn together in a dome shape, in addition to the bill. Hold the tape measure flat along each seam of the hat to get an accurate measurement. Note each measurement.
Mark the dimensions of each section on the reverse side of the transfer paper. Connect the points of each triangle to form the entire perimeter of each section.
Repeat the process for the brim of the cap, which is a broad, slightly arched shape. Measure around the outer edge of the brim, first. Hold the tape measure against the fitted portion of the cap. Measure up the side, across the front, and back down the other side. Note the total measurement in addition to the points where the bill angles or turns.
Hold the tape measure perpendicular to the bill, flat against the cap, to measure the fourth side of the bill. It will be difficult to get an accurate measurement if you hold the tape measure down flat on top of the bill because the tape measure is straight, but the line you are measuring is curved. If you orient against the cap instead, you can curve the tape measure with the curve of the cap and bill. Mark the fourth bill measurement to form the complete bill shape on the transfer paper.
Cut each section out of the transfer paper.
Lay the hat as flats as possible to facilitate ironing. You will work one section at a time, so you only have to worry about keeping one section totally flat at any given time. Working at the edge of the ironing board may make that easier.
Line-up a piece of transfer material with its corresponding section on the hat. Hold the hot iron to the back side of the transfer to begin the transferring process. Run the iron over the entire surface of the transfer. Pay particular attention to the edges.
Follow the manufacturer's instructions to determine how long to iron each section. Since you are working on a textured, non-flat surface, you may want to exceed the recommended time to ensure that you have thoroughly transferred the design to the hat. As long as the transfer paper is not burning, you can continue to iron.
Remove the iron from the hat. Allow the transfer a moment to cool. Peel back the transfer paper.
Repeat this process on each section, until you have covered the entire hat.