(Or, When was the last time you changed the white ink cartridge in your printer?)*
Inkjet transfer paper is used to transfer images or text onto a wide range of suitable fabrics. Often used on t-shirts, it is commonly referred to as t-shirt paper. The product is available for light or dark fabrics and so it is not always clear whether your fabric falls under the dark or light categories and which one will suit your project better.
The Difference Between The Two
(or Is my garment light coloured or dark colour)
Ink relies on a white background to be visible and produce accurate colour reproduction. If you replace the white background with something dark, ink becomes translucent and on black backgrounds, it is totally invisible.
So if you are going to print a white t shirt you clearly require the light transfer paper.
If the colour of the shirt is other than white, but not too dark (pink, yellow, light blue etc) the light transfer paper can still be used with some images. Black text and dark graphics will still work well. If however the image is also light in colour and contains pastel coloured images, the colour of the shirt will start mixing with the colour of the image producing results different than what appears on the paper.
The decision of which paper to use on garments other than white lies in the combination of the colour of the shirt and the colour of the image. In general terms, a dark image works on light coloured shirts but a light image will only work well on white.
When using coloured garments, in order to guarantee the image appearing on the garment exactly in the same colours as appears on the paper, you need to use the dark transfer paper when printing dark garments.
It works by transferring the white background together with the image. When transferring an image printed on the dark transfer paper, the image on the garment will look EXACTLY as it appears on the paper, INCLUDING all the white edges and spaces in between the image. As a result of this, images which are suitable for use with the dark transfer paper on dark garments are limited by design and should be either block images or ones that can be cut around to remove the unnecessary white areas.
You could also design an image with a solid background or try to match the background of the image with the colour of the shirt to solve the limitation of the dark transfer paper.
Both papers can be printed on an ordinary inkjet printer with ordinary inks. They are transferred with the aid of a domestic Iron or heat press and will work on a wide variety of substrates and garments. The packs contain all you need to achieve great results
*And yes, you were right. There is no white ink in the printer, hence the two different transfer papers.