I have a Sheaffer Valiant with a Triumph medium nib and recently started carrying it around in my shirt pocket as my 'go to' pen.

I filled it with Pelikan ink - a mixture of black, blue-black and blue that is a nice dark blue-black. Once the ink starts to flow, the flow is rich, wet and steady but it often fails to start first time but requires a bit of coaxing to begin.

The slit in the nib seems to lose its ink, if you see what I mean.

Restarting has involved wiping the ink along the top of the nib from the breather hole, dipping the nib into ink or even unscrewing the touchdown mechanism and withdrawing the punger a little and putting it back (this is sometimes too effective and leads to blobs on the paper!)

Help! Is it the ink, is it the pen or is it just not suitable for my shirt pocket?
None of my other pens have done this no matter what ink is used.

Chris