I shake my bottles just enough so that everything is evened out, then I let it sit for a minute or two to let any bubbles that have formed settle down. I don’t shake rigorously, I just sort of turn the bottle over several times sometimes changing directions. You can tell when you’ve gotten everything well-mixed.
You will see some people claim that you should NEVER shake a bottle of ink. This is simply not true. There are occasions when you should shake your inks and where you should not:
- You should not shake bottles which you suspect may be suffering from “something/slime/sludge/sh*t in the bottle (SITB)”. SITB is caused by contamination or chemical changes in the ink. You can easily distinguish this. Often the consistency of your ink will change to slim or you will have slimy threads floating in your ink. In cases, of mold contamination, the ink may take on a strong ammonia smell. Shaking will not solve these problems and can result in a clogged pen. If your bottle is suffering from SITB you should throw it out and replace it. Any pen you’ve filled from that bottle should be thoroughly disassembled and disinfected with a solution of ammonia and water.
- You should shake your inks if it seems that the color has separated a bit. In particular, you should shake any Noodler’s Bulletproof inks. The chemical make up of Noodler’s bulletproof ink is such that it needs to be shaken if you want it to remain the same color and have the same characteristics. The maker of Noodler’s inks suggests that you shake the bulletproof inks. Additionally, there are some specialty or limited edition inks that require a shake. Noodler’s Dragon’s Napalm and J. Herbin 1670 ink, for instance, contain a sort of metallic dust that goes out of suspension if the bottles sit for a while. You have to shake them to get the particles back into suspension.
If folks want to disregard manufacturer’s suggestions and ink characteristics then that is their business, but they certainly should not complain when they get inconsistent results.
Often opponents to shaking ink argue that if it can separate in the bottle it can separate in the pen. Well, yes, of course it can. However, you should never experience this so long as you actually use your pens on a regular basis. It should be painfully obvious that the mere action of picking up your pens and writing with them results in the ink being sloshed back and forth thus keeping everything well-integrated.
Now, if you fill the pen and let it go unused and unmoved for weeks or months on end then who knows what you’ll end up with.
I’ve only ever had one ink precipitate out while in the pen. It was an iron gall ink, and I hadn’t used the pen in a couple of weeks. I simply agitated my pen and the particles went back into solution. I had no clogs, and wrote the pen dry with no problems at all.
FPN member SamCapote made a post entitled Normal Sediment in Fountain Pen Ink (with Photos) . This is a good reference point if you are trying to distinguish between sedimentation and SITB.