humans have different biases towards what they think is neutral and often what they see as neutral. the only method to discovering what any one particular human sees as neutral would be to have them dial in red, green and blue light until the do not perceive any more red than green than blue… And then at that point. comparing them against other humans you can map out color blindness (just in case they have some) and we arrive at what is neutral for you in regards to white light. This could be done also at 50% gray.
When we made Piezography Neutral inks - we used the ICC concept of “neutral” (which is along that line above which I wrote) and we decided to make what is perceived by the “standard human” (one without any color blindness) as “neutral” on a standard grade of paper (we chose Hahnemuhle Photo Rag).
Will you see Neutral inks on Photo Rag as “neutral” - I do not know… You may not and it can be because of bias (personal) or bias (color blindness) or a combination of both.
But, I do know that you should not see Selenium inks on any paper as neutral. If you do - it definitely confirms a large personal bias or some color blindness. So you should stop trying!!!
I just looked at all your test prints again and I noticed that you have printed on a lot of warm papers that you sent us and what I see is warm paper under very light amounts of Selenium inks - and the ink can not make the paper warm white appear “neutral” nor even less warm - until about 50% coverage - maybe somewhat less - and then the ink is still influenced by the warmth of the papers you are selecting or the warmth of the paper combined with the coating.
i understand why you like warm papers - but I do not know how you can make the papers less warm other than by printing with color inks and using ICC color management to have the color inks counteract the warmth of the paper. Of course it will not be able to do that to the highlights and near highlights.
I suggest instead - that you use near white papers and stop using warm papers. the warmth can not be eliminated from your images if you print on warm papers. I suggest you switch to Piezography Neutral inks.
Dana’s suggestion is a very inexpensive way for you to determine if Neutral inks on more standard whites is “neutral” to you. If it is not - and its too cool - then you can move the inks to warmer papers such as you like. If you see the neutral as too warm - then you can shift it to brighter white papers.
We can serve you up achromatic neutral - but in the end you have to arrive at something you consider to be neutral and a neutral you are happy with. That will necessarily demand that you select a paper - not because you like it it - but because you like the color of the neutral inks on it. in a way - its just like darkroom printing in that regard. hope that makes sense!