Some months ago, we ran into a time where we resorted to buying our own ink refills because they were almost never available amongst the stationery supply. At the shop in town I usually visit, there was an entire shelf of them, though looking a little different from those I'm accustomed to using. I checked to make sure they're for whiteboard markers and grabbed a couple without giving any further thoughts to the differently-coloured packaging.
When I started using my newly-purchased refill, I noticed that my marker's ink started fading - and I mean, the more ink I put into it, the more faded the writing appeared! It made no sense at all. Eventually, it was rendered totally useless, for the ink then appeared so light it was ghostly. I called it my Ghost Pen, and stopped using it.
It was then that I took some time to really look at the refill ink I bought. I noticed they were indeed meant for a different range of markers than those we've always used.
So, the difference is the ink being "alcohol-based" whereas my markers were simply... well, regular whiteboard markers, I suppose. I don't know what could be so disagreeable about alcohol-based ink with my markers, but somehow, when used together, they turn translucent. So, I was back to the running-out-of-ink predicament, plus I have bottles of ink I then had no use for.
I went to the shop again, and this time, made sure I got the right kind of ink. I also got a couple of alcohol-based markers, since, I figured, I already have the refill ink for them.
The cashier, scanning the bar codes of the items, gave me an odd look. "These refills are wrong for the pens," she told me, meaning to be helpful, I'm sure. I started saying, yes, I realise, but... and it dawned to me I really didn't want to have to tell her that the current purchase was to right a wrong I made the last time. I didn't think she'd be interested. Actually, I'm not sure you, Reader, are interested either.
And now I wonder what I should do with the one which has already turned into ghost...