I think you've misinterpreted what a "mixed ink" is.  It is there so in Indesign you can specify a swatch that is made up of 2 colours combining to make a third colour.  Even with a mixed swatch of standard Pantone colours there is no way to soft proof it reliably, it even depends on what colour goes down on the page first, let alone stocks and precise ink weights and densities.

You could go and talk to your ink supplier but I'm  sure they're not official Pantone colours.  And trying to soft proof it is an exercise in futility.  The reason for the "Extra Strength" is usually for greater lightfastness but might be used by your supplier to mean something else.  As for driers they are normally transparent, what type of drier is it, Grapho?  I've never heard anyone trying to mimic what they look like before!

What you need to do is create a swatch that is named something like Special mix, is a spot colour, and is a CMYK representation of what you are trying to get.  Then you get a draw down of the actual ink mix and show that to the customer along with your proof, making it clear that in the actual job the colour in question will be printed like the draw down.  It's not easy, but there is no other way to proof custom spot colours.

Well if you know what mixed inks are you are using them wrong!

Say you have a mixed ink swatch in Indesign with  50% Rubine and 50% yellow.  Indesign will then output a PDF that calls for both Rubine and yellow plates.  What you want is one plate with your spot on it.  Whereas if you did it the way you're describing it you'd even have a plate for the drier!

You will be mixing that ink you have with scales and an ink knife, not inside Indesign.

Again, I say you will need to create a spot colour in Indesign to represent that colour you're making.  Call it "Shell Corporate Red" or whatever you want but it is not a mixed ink swatch.  This stuff is bread and butter to me, I've physically mixed inks, printed, made Indesign files, supplied files to many different prepress houses etc etc.

OK, that is a much better question.  I'm not missing your gist but mixed inks isn't the answer.  Unfortunately there's no easy answer to it.  What the ink formula will create on the press is something like a custom pantone colour, as I said in my first post there is no easy solution, what is typically done is a "dummy" swatch that looks similar is created.  I stress again that there is no accurate way to create it but this is what I would do:

First of all load your Pantones into Indesign, ignore the Hi Strength, it's all you can do and in my experience they don't change the actual colour that much anyway, particularly if they both are.  Then create a mixed ink swatch (I know I told you not to.... just hang on).  But don't make the percentages the same as your formula, you need to use math and make the ink that has the highest percentage 100%, ignore the driers, they don't alter the colour.  So if I had a formula of 71.4% Rubine and 28.6% Yellow I'd go 28.6 divided by 71.4 multiplied by 100.  The 71.4 becomes 100.  See below, if you supply me your formula (use other colours if you want, but supply the percentages you have) I'll work it out for you.

Then make a box using that colour as a 100% fill.  Go into the ink manager and tick "All Spots to Process".  Export to PDF.  Open that PDF in Acrobat and open the Output Preview panel (Advanced > Print Production > Output Preview).  Put your cursor over the colour and write down the values shown, see below:

Then go back to Indesign, delete the other swatches, turn off all inks to process and make a new one like this:

Done!  Export to PDF and open the Output preview again and you will see a single spot colour.  Again, I will stress that this is not an accurate way to do it, that would be mixing the ink, printing it on the press, and choosing a close CMYK mix off that.  Others might be able to suggest better ways for doing it purely in software.

Neither was I!  Go 44.74 / 52.26 * 100 = 85.6% for the Rubine and use 100% yellow.

You do realise this is seat of your pants stuff?  At the very least I'd give the formula to my pressman to mix, get him to do a draw down (scraping the ink very thinly on card with a metal ink knife) then compare that with what you're seeing.

Usually for corporate colours a style guide is created which takes care of all this type of stuff...

Hello, this may be slightly unrelated, but please let me know if you can help:

I have created a mixed ink swatch (3 pantone neons colours: 2 used at 100%, 1 at 30%).

I have done a wet proof and it works well, but I also want to use tints of this swatch in my document, and InDesign wont allow this (i.e. when I go to 'New Tint Swatch' it is greyed out.)

I thought I could create a new mixed ink swatch with the same colours used at 50% and 15% but in essence, that would be creating a new swatch, no?

Any advice on this is greatly appreciated.

Thanks, but I left out that I am using this 'mixed ink swatch' within a blend, and in that case the opacity slider isn't an option.

Alternatively, I could use create a new 'mixed ink swatch' with different readings (i.e. 50%, 50%, 15%) but isn't that in fact creating another spot colour?

As I understand it, a "mixed ink swatch" is a bespoke spot colour, mixed by myself, right?

So if I change the percentage of each component colour, am I not creating a new swatch?

Sorry if I have got this wrong, it just occurred to me that I may have misunderstood it.

I see, but in this instance I don't want to use the existing base inks to create a colour, but rather want to create a new base ink by mixing 3 Pantone neons. So, in order for the printer to do this, I created a "mixed ink swatch", but it sounds like I may have gone about this the wrong way? I thought I was essentially creating a new, 'bespoke' spot colour. Thank you for your help.

I see. So, if I want the printer to mix one custom colour, should I simply pick a spot colour that looks right on screen and then tell the printer to mix the custom colour and replace it before going to press?

Well, I want a strong neon red, and nothing else comes close as far as I can see.

But it's not a problem as I've done tests and the resulting colour is good, just not sure about the best way of creating a bespoke 'spot' colour within InDesign (and doing tints and blends, and all that). But reading what you say, I think it's safest to do a normal Warm Red, and then tell the printer to replace it with the special neon red on press. I am in UK time, so leaving work now, but thank you for your help!