I presume you are referring to an old fashioned fountain pen that you fill from a bottle of ink. There is a small flexible rubber sac inside the barrel of the pen which can be compressed by a lever. When the lever is released a partial vacuum is created in the sac that sucks up the ink. I haven't used one in years but remember having received one as a gift from my grandmother when I graduated from high school. There is a very nice article in Wikipedia about these types of pens:
dettol works
an ink filler a hand pump a medicinal dropper
The way invisible ink works depends on the method used to make it.
ink jet printer
Lemon juice
Yes, mixing tattoo ink is done every day in the tattoo studio. It works pretty much just the same as mixing any other kinds of ink.
you press the end with ink against paper
An ink thermometer works by measuring the temperature of the ink inside a container or within a printing press. It typically consists of a temperature sensor that detects the ink temperature and displays it on a dial or digital readout. This information helps ensure the ink is at the optimal temperature for printing and prevents issues such as color variation or smudging.
If it is ball point pen ink, spray the ink with ordinary women's hair spray, and launder the shirt immediately. This works like magic. If it is liquid "fountain pen" ink, it may be permanent, I'm afraid.
Semen usually works. References: Personal experience.
This works for ours:Porelon NR-42-2 Replacement Ink Rollers, Pack Of 2 Item # 848564 at Office DepotClosest it says is el 1801V, but it still works.
Any HP photo ink will work well, owing to its sunlight protection and anti-fade inks.