I use 4 color catchers in a large load of new fabric. I have never had a problem with colors running. I also remember hearing that you should make sure you don't throw the color catchers in the dryer with the fabric, and that is what I do. Really don't know whether this is important or not, but being as I have never had a problem I continue to do it. I didn't know that you can reuse the catchers if they are not saturated with color. I will be trying this.