If you are putting the designs on any color shirt besides white - and you are using light transfers - then all white areas of the design will be clear or the color of the shirt.
With dark transfers, all white areas of the design will be white. I personally use dark transfers for everything - including white, but that's just a personal preference. I like that the dark transfers have a matte finish (not shiny), that I do not need to flip/rotate the design first and that the colors are more vibrant with a dark transfer.
If you are on a hunt for dark transfer paper - see my webpage (link below)
thanks for the info-i am going to check it out.
