Hi, I wanted to know at what point in the process it should be used, whether it should be added to the colour and in what percentage?

The Quasar Modatex Ink should be diluted with water to achieve the right viscosity; then the ink is removed from the frame and the cleaning is carried out, so that the frame can be archived correctly.
Retarder should be added in the amount of 1% to 3%. Excessive doses impair final drying and the printed ink will remain water-soluble for a long time even after baking.

Therefore, the advice is to add water until the correct consistency is reached and add the retarder percentage at the end.

As there is no precise dosage for adding water, one must adjust the amount a little at a time and use experience.
The correct procedure is as follows

get an empty can and pour into it the amount of ink you consider necessary for the printing session;

add water a little at a time, stirring, until you get the consistency of Nutella or mayonnaise;

the ink is now ready to be used;

nothing forbids, during printing, to still make small corrections directly in the frame: it all depends on whether the ink passes easily through the canvas, or struggles to pass and requires excessive squeegee pressure.

it is convenient, at the end of the job, to recover both the ink left on the frame and the diluted ink left in the jar and pour it over the canvas.

If the ink is too diluted the print is likely to be smudged, if the ink is too thick you will struggle to get it through the frame when printing.
We usually recommend using a 55-thread frame, as water-based inks dry quickly on the frame, clogging the mesh and making it unusable once the ink dries.
This is why using a slightly wider spinning allows the ink to dry less quickly on the frame.