Tee designs on Spindle require artwork to be supplied according to the following specifications:

• A maximum of 400mm x 450mm dimensions
• A PNG file at 300dpi (either CMYK or RGB is fine)
• Your artwork file should not exceed 20MB
• Ensure that all 'transparent' areas of the artwork are actually transparent, rather than a background colour. More clarity on that below.
  

What do you mean by transparent areas?

If your design is placed on a background colour you have to be sure that there are no unintended areas of colour that match the background colour - thus seeming transparent.

This design, for example, is on a white background.

If we change the background colour of the artwork, however, we can see that there are unintended areas of white that have been used to create the illusion of transparency.

Gee dang. That's not what we want! We have to make sure that this design will look as expected on any t-shirt colour, so we have to remove it. Then, when removing the background colour altogether, there should be no unintended ink printed in places we don't want. Like this:

Nice! Now, this design can be applied to any colour of tee and it will look how we want.