Octopus Write and Draw pigment inks

[Karmachanic]

@JulieParadise mentioned these in a post, so I went looking.  Here's what I found.  Available in 10 and 50ml bottles

 

[dipper]

That's interesting. And I see Octopus have lots of products, beyond pigment inks.

 

Inks for refilling inkjet printer cartridges are one type of Octopus product. Colours there are Cyan Yellow Magenta and Black ("CYMK"), the subtractive colour primaries.

 

So it makes sense that Octopus also make the same four CMYK colours in a fountain pen ink formulation, as a kit for mixing your own fountain pen ink colours.

https://www.octopus-office.de/shop/en/2525/rimik-rainbow-ink-mixing-kit-for-fountain-pens

From the photo above these inks appear to be transparent, dye-based inks. (The safer and lower maintenance option for fountain pen use.)

Price seems reasonable. 32.95 Euro for a total of 200ml of ink in the kit equates to 8.24 Euro per 50ml bottle of mixed ink.

 

There is also a fascinating colour mixing chart. My first thought was to doubt the accuracy of any such chart. But, on further reflection, combining exact measured proportions of CMYK ink dots to give predictable colours is how inkjet colour printers work their magic. So Octopus are well placed to transfer their expertise in colour printing inks over into fountain pen inks.

 

Decoding the chart, I hope this is correct:

 

Nine reference points around the edge of the colour wheel ("saturated" colours, or high "chroma" colours) are

1 Yellow, 2 Orange, 3 Red, 4 Magenta, 5 Purple, 6 Blue, 7 Cyan, 8 Teal?, 9 Green.

 

The table shows how to mix those colours. "Colour 6 Blue", is 5 parts cyan mixed with 1 part magenta. "Colour 5 Purple", is 2 parts cyan with 5 parts magenta.

Given those reference points we could aim for our personal unique saturated purple-leaning blue ... perhaps 2 parts cyan with 3 parts magenta.

 

Any saturated colour mix can be "dulled", moving towards the centre of the colour wheel.

In budget printers that can be done using combinations of all three CMY colors. Improved colour gamut (ie more colors) can include black (K) in the mix.

 

In the ink mixing chart the yellow bar, fading to dull khaki, shows the result of mixing black (K) with pure yellow. The same sequence is repeated as a radial line on the colour wheel.

 

The black (K) mixing ink here is clearly nowhere near the concentration of a typical black fountain pen ink. It must be designed for this specific mixing purpose.