Is there a way so the blend consists of various hues of the Pantone colors, rather than CMYK values?
I guess, if it's possible to change the blend into a simple gradient going from spot color 1 to spot color 2 it solves the issue in a simple way, but what if that isn't possible? What if you blend from 2 different shapes? Because that is one of the things I would use the blend tool for. Otherwise I'll apply a gradient instead. Here is what I tried out:
Create style effect on both ends
Create a style effect on both ends of the blend, using 2 fills on top of each other via the Appearance palette. For one end of the blend you use spot color 1 as a first fill with an opacity of 0%. On top of that you create a second fill using spot color 2 with 100% opacity. Then for the other end of the blend you use spot color 1 for the first fill with 100% opacity, and on top of that you have a second fill of spot color 2 with 0% opacity. Then you blend both ends. You might need to enter specific steps for the blend…
When I thought of this idea, I was thinking "Aha! This is probably it!", but when I tried it out, I ended up with this moiré effect. You get to see the in between steps of the blend. Adjusting the blend, using a higher amount of steps didn't seem to help either. It even took a few seconds until the result was rendered. Something that usually doesn't happen when I use the blend tool. It didn't feel and look right.
And so I tried something else…
2 blends on top of each other
I was thinking of trying 2 blends on top of each other, each using the same spot color in the blend but going from 100% opacity to 0% and vice versa. So here is what you need to do:
Create a blend using spot color 1 going from 100% opacity to 0% opacity. Duplicate this blend on a new layer on top of this one, and make the blend with spot color 2 going from 0% opacity to 100% opacity. This way you always make the blend with the same spot color, only you lay both on top of each other.
I haven't tried this out in real life (meaning taking what I created to the printer), but I presume this will render things the way it should using only spot color values and not CMYK values instead. If anyone has a better, smarter way of doing this, please don't hesitate to share.