Screen Printers Open - A Forum for Screen Printing and Embroidery

the RGB mixture that you mentioned is close to Pantone PMS 721 which, using standard litho inks calls for
5.3 grams of Pantone Orange (021)
1 gram Pantone Black
93.7 grams of Transparent White.

in the proprietary Union Mixopake System it calls for
93.1 grams of their Super White
5.8 grams of Yellow (red shade)
.9 grams  of Red (yellow shade)
.2 grams of Black

Are you noticing a trend towards white that was absent in your formula?

The Wikipedia entry on RGB starts with this

The RGB color model is an additive color model in which red, green, and blue light are added together in various ways to reproduce a broad array of colors.

and continues talking about electronic input and output devices associated with this color model.

So, no, I don't believe that other than using an RGB color in a graphics program, and then finding a CYMK or Pantone cousin, it is of any use.
If I were you, I'd ignore pantone matches, but mix by eye starting in the ballpark of the two examples I gave you.

Document all weights of component colors if possible to aid repeatability.

Thanks alot. 

Will give it an eyeball and try my best.  Also will expect the ink to darken up some when dried, of course.
Frog, yes there is a lack of white which is expected in the RBG.

Killer, thanks for the doc.  It is very helpful.  So basically, taking a random example of

PANTONE 165 PC
C:0 M:68 Y:98 K:0

TO acheive this color you can mix by weights according to the CMYK numbers as weight ratios.
Also since this must be done with process inks, the final ink may  be very transparent.

I know that most on here print on textile, but all i do is flatstock, but the science is still the same.

Also not familiar with Pantone, but am learning about.  Just trying to find mixing formulas that could
be applied to Speedball or some other similar waterbased acrylics. 


Guess it will be a time of trial and error for a time here to get everything dialed in.

Thanks for the direction once again.

James, you can't mix RGB inks. Yes, RGB is additive, it's also about light, not ink. When you combine RGB full values, the result is white light. Red, Green and Blue are the primary colors of white light. If you mix Red, Green and Blue inks, you will get a bucket of mud. CMYK is the subtractive process, because, White light with the Red subtracted out leave the Green and Blue, which is called Cyan. White light with the Green subtracted out leaves the Red and Blue, which is Magenta, and White light with the Blue subtracted out leaves Red and Green, which becomes the Yellow, which sounds weird I know, but accept it as fact. Now, in theory, if you put 100% Cyan, 100% Yellow, and 100% Magenta on top of each other, you will get Black. But that doesn't happen, mainly because the Cyan, Magenta and Yellow inks are not 100% pure, causing the breakdown in theory/practice. Thus, Black (K) was added to the mix, and only prints in the deepest of shadows.

Steve

We love Matsui, it's so easy to use.  I haven't used speedball in about 6 years but when we first started incorporating Matsui products into our shop I remember being blown away that I would walk away from the job mid-print and take a phone call without the screen clogging up like crazy.

I wonder if it would be possible to mix in some Speedball black with the Matsui 301.
The Speedball black dries very chalky and scuffs so would like to use it up if possible.

Nope, unless you want to ruin your nice Matsui ink.

Save the Speedball for what it's good for - occasional printing of light colored shirts or paper when you run out of any other ink.
 


For the Matsui Pantone matching, I find that the darker colors and pigments seems to be much stronger than the formulas recommend. Mix in your light colors first, then add the darker colors a little at a time up to the recommended percentages.

Also, the formulas assume the inks are being printed to a white substrate, so you won't know the exact tone until you print it. Looking at the ink in the container it will usually look much darker/denser than it really is.

Go slow, use a good scale and mix in small batches.