The swabs show how close the colors of Infra Red and Poppy Red are.
However, Caran d’Ache Infra Red is more orange and less saturated, and shades more. Diamine Poppy Red is more saturated and is closer to straight red.
Both inks have behaved similarly for me. They both are on the wetter side, and both flow nicely. Perhaps because they are well-lubricated, I have experienced nib creep with both inks. However, that’s been minor, limited small droplets of ink on the top of the nib. I didn’t get ink in the cap.
Evaluating each in a Safari/Al-Star with medium nib, the line width seems the same as well, with both running slightly on the wider side. In this photo, Caran d’Ache Infra Red is on top and Diamine Poppy Red is below.
Both inks have decent water resistance, but neither is waterproof.
I found each ink fairly easy to clean from converter pens, especially for red inks, but each was only in the pen for about a week.
There is a big divergence in price. Diamine Poppy Red really has the advantage there. In the US, Diamine inks are about $15 for an 80 ml bottle or $7 for a 30 ml bottle, whereas Caran d’Ache inks sell for $32 and up for a 50 ml bottle.
Caran d’Ache inks do come in a truly spectacular and useful bottle, and I could see that being a factor. But Diamine’s bottles work, too, and Diamine gives a buyer the option of buying only 30 ml.
Paper towel chromatography reiterates how similar the ink mixtures are. However, just as in the writing samples, the Diamine is more saturated and redder, while the Infra Red shows comparatively more orange and has a softer profile. The photo below shows Caran d’Ache Infra Red on the left and Diamine Poppy Red on the right.
Both are beautiful red inks. Both are friendly and cheerful. Both hold the page very well. I find the shading, the lower saturation and the orange-red color of Caran d’Ache Infra Red almost irresistible. But I am trying to resist, because Diamine Poppy Red is also gorgeous, and is a great value, although more of a straight red color.