Is there a method by which you could make your own ink for refilling inkjet cartridges?
InkJet ink is made to very high tolerances because it needs to have precise density and drying characteristics in order for the printer to work properly. The ink itself is pretty uniform accross cartridge designs, though. You can buy big bottles of ink and a little syringe-like device to refill cartridges if you don’t want to buy new ones.
Here is an example of what I mean.
I’m sure it would be possible, but would probably involve setting up some kind of small-scale industrial process.
The best inkjet ink are pigment based - made of small insoluble coloured particles, as opposed to the cheaper ones that are dye based - made from soluble, coloured chemicals. The problem with pigments is that they tend to cake and drop out of suspension over time. Quality control would also be an issue; your printer drivers are configured to expect the inks in the printer to be quite precise shades - if you got the colour wrong, it would be difficult to adjust to compensate (perhaps impossible - I suppose it would not be at all difficult to end up with a set of ‘wrong’ primaries, from which certain colours simply couldn’t be mixed in combination)
It probably just isn’t worth it - the cost of equipment and materials to make a serviceable product would probably far outweigh the saving for even the heaviest user.
Are you hoping to save money, or are you after non-standard colours, such as gold?