I rarely print on mat (matte) papers. But now and then I must, usually because a client job requires it. I had just such a job yesterday. I made 36 small prints on Epson Ultra Premium Presentation Paper, known long ago as Enhanced Matte. I keep this paper in my inventory of sheet and roll stock primarily to service three clients who, for their own reasons, insist upon it.
The MK in my printer is the only remaining ink cartridge that came with the printer, a 90 ml "starter" cartridge. It's well past its expiration date. Until yesterday, the last time I did a PK to MK swap was 23 March, 2014. I swapped back to PK on 4 April.
Yesterday I initiated the swap, and then performed a nozzle check. The 7900 does not automatically clean after this swap; it DOES auto-clean after swapping from MK to PK. The nozzle check showed about 50% of the MK pattern missing. I performed a standard cleaning of the MK/LK pair, followed by a nozzle check that showed a tiny nit missing from the MK channel. I ran the print job, finding no problems with any of the prints.
When finished, MK showed 4% remaining. Obviously I need to order an MK cartridge, which will be the standard 130 ml, which will likely last as long as I own the printer. Heck, the current 4% cartridge could very well serve for many more months, although at that low a level the printer will refuse to do any cleaning that includes the MK channel, hence the need to buy an MK.
As long as MK is loaded, I'll make a few prints of my own work, These are pieces that sell reasonably well, look best on mat paper (I'll use Epson's Hot Press Natural), and which I print several of on those rare occasions when I've got MK loaded. I'll swap back to PK with the next print job that needs it.
--Jay