I will try to explain this in this post.
Traditional printing always relied on the 4 colours mainly Cyan, Magenta, Yellow and Black. More often referred to as CMYK. There is actually a fifth colour that is in place that most people do not realise and that the colour White. When we talk about CMYK printing, we are assuming that it is being printed on white paper.
Why is this important?
Well mainly because CMYK can be combined to form a lot of colours but it can never form white. But that is just one part of the story. The other reason is that we need the white from the paper to create many of the colours that we see.
Let me give an example. Suppose you want a light shade of yellow.
How do we achieve this? The yellow toner/ink that is in the printer is already a pre-determined shade of yellow. Usually something like this shade
To create a lighter colour what the printer does is that it will actually space out the yellow toner/ink when it is printing. This means that more white is seen and less yellow giving the illusion that it is a lighter shade of yellow.
So now you must be thinking .. “If I am not printing a light shade of yellow but I am printing a deeper shade of yellow then the base colour does not matter right? I do not need white in this case!!”
Wrong!! And that’s my next point.
Toner/ink is not opaque
The second point to note is that toner/ink is not opaque and will mix with the colour of the media. Think of it like using a yellow highlighter pen. When you highlight on white paper, the yellow highlighter really stands out. When you highlight on maybe pink paper, it does not stand out as much. And when you try to highlight onto black paper, you see nothing at all.
We need white to see the correct colour when we print onto a dark t-shirt So when the T-Shirt is white, we can print directly onto the T-Shirt because the surface that we are printing on is white. So all colours will be seen. This is how our TTC transfer media works!!
However, we cannot do the same thing with a black T-Shirt as the surface that we want to print onto is now black. In order to accomplish this, we need to have a layer of white from the media. Our OBM Transfer media is exactly that!!