Questions have been asked about ink going stale. I asked Epson about this.
In response to some questions floating around on the internet about whether inkjet ink can go stale, I put the following questions to Epson:
Does Epson’s inkjet ink have a ‘useby date’ before it goes stale, both for unopened cartridges and for opened ones once in the printer? If so, what is the cause? Is it oxidation or some other process? Do the cartridges have printed use by dates on them or advice to use within a certain time of opening? This is for a story I am doing.
Epson’s official response was:
Epson’s inkjet cartridges have an install-by date shown on the packaging and, included on the cartridge management chip is the cartridge production date. Depending on the type of cartridge/ink the install-by date is either two or three years from the production date. Users can check the production date on the chip through the printer status monitor.
When a user installs a cartridge the printer driver checks the chip for the production date and calculates the install-by date, and if the cartridge is beyond its install-by date the printer status monitor provides an on-screen warning. The user can continue to print with that cartridge if they wish.
As per the user guide on the CD supplied with the printer, Epson recommends that all inkjet cartridges should be fully used within six months of being installed in the printer along with Epson genuine paper to guarantee the quality print output expected from an Epson printer.
The reasons for the install-by date and the recommendation to use within six months are: some chemicals in the ink tend to oxidise and evaporate over time, and this changes the viscosity of the ink. As you know, Epson printer drivers expect the ink to be a certain viscosity at a given temperature and a reasonable departure from that may cause the printer to lose some control over the size of the ink droplets. This same problem occurs with third party inks because the viscosity is completely unknown. This may mean some reduction in print resolution and/or the smoothness of tonal gradations.
Obviously once the ink cartridge is installed on the printer after being removed from its vacuum packing this process can occur faster, hence the recommended in-use life of six months