We use a Japanese brand glue on our patches. This glue is applied over the plastic backing of your patch. It's an invisible layer, but it's there.
This particular glue activates at 260-280 degrees Fahrenheit. You should aim to heat up your iron to 270 degrees.
You won't find an actual temperature setting on household irons. They'll have a silk setting or a cotton setting.
You should use a frying pan thermometer to find the correct setting of your iron.
Place your iron on your ironing board with your frying pan thermometers probe sandwiched between the iron and the board. Turn your iron on to it's lowest setting and see where the temperature goes to on your thermometer. You don't want to be exceeding 280 degrees Fahrenheit! Lift up your iron and let it cool before resuming the test if the temperature goes over 280 degrees! You'll notice it's a pain in the neck to find the correct setting that will hold a 270 degrees temperature for 30 seconds. But after fiddling around you'll find that you can maintain the required temperature for a short period of time. It takes a lot of practice to iron on a patch properly with a household iron. The hardest part is finding the right temperature setting of your iron. The annoying part is the temperature fluctuations of household irons.
Final words - Don't iron on a patch to leather or nylon material. Heat will damage your material. The patch will stick, but your leather will scorch from the heat!
