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Old 11-15-2017, 03:17 PM
contumacious contumacious is offline
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Single Pigment Colors That Cannot Be Mixed

Is there a list somewhere of the single pigment colors that cannot be precisely mixed from a combination of other single pigments?
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Old 11-15-2017, 07:14 PM
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Re: Single Pigment Colors That Cannot Be Mixed

I am not aware of one.
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Old 11-15-2017, 07:34 PM
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Re: Single Pigment Colors That Cannot Be Mixed

"Precisely" is, alas, imprecise.

Do you refer only to masstone? Transparency? Breadth of spectral peak? Secondary spectral peaks, and their breadths?

As a rough guide, I would find a resource that lists pigments in terms of hue, chroma, and value. It is my understanding that the chroma of a blend is less than the highest chroma of the components, and that the value is less than the highest value of the components.

There are some high-chroma pigments (especially in orange and yellow-orange) that are surrounded in hue by lower-chroma pigments. Thus, I would expect those pigments could not be emulated by a blend. I believe that some of the Hansa Yellows are in this category.
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Old 11-16-2017, 03:52 AM
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Re: Single Pigment Colors That Cannot Be Mixed

I'm not aware of such a list. But just playing with the various pigments available in the art world, you'll find there are many colors which cannot be mixed - either as a unitary (single area of) color, or their idiosyncratic real-world nature (the duo-tone of transparent colors, granulation of some pigments in watercolor, bronzing effect of Phthalos, opacity, tinting strength etc.).

If you look at a good color wheel in which the pigment placements were done by a spectrophotometer, a lot of the colors on the periphery will be unmixable. Some colors that aren't near the periphery on a 2-dimensional color wheel/plot will also be unmixable because they might not be high chroma, but are of high saturation. A few of the non-primary colors which cannot be matched (close enough for practical purposes maybe, but not a match in chroma) :

-Ultramarine Blue
-Dioxazine Purple
-Phthalo Green YS and BS
-Pyrrole Red
-Pyrrole Orange
-Cobalt Teal?
-Isoindolinone Yellow
-Nickel Azo Yellow
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Old 11-16-2017, 04:04 AM
Mythrill Mythrill is offline
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Re: Single Pigment Colors That Cannot Be Mixed

Patrick, you're probably referring to PG 50 when mentioning Cobalt Teal (also sold as Cobalt Turquoise Light), right? Because there are two variations that can also be sold as Cobalt Teal: PG 36 and PB 28.

But wait, isn't PB 28 Cobalt Blue?

There are more recent variations of Cobalt Blue that actually have a light blue-green color. They're similar to the bluer variations of Cobalt Teal/Cobalt Turquoise Light, but are an even brighter blue.

Here's a Blick swatch of the lighter version of PB 28:



Also, it's important to remember there's no color that matches any white in any way (except for the whites themselves, naturally).
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Old 11-16-2017, 04:21 AM
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Re: Single Pigment Colors That Cannot Be Mixed

Mythrill - yes I mean PG50 - the one Golden used to have but afaik has now been replaced with a mix. It looks very close but I don't have either to try a side-by-side comparison, hence the question mark.

Another example of an unmixable (or at least unique) color is Chromuim Oxide Green which has extremely high opacity, lightfastness, and a peculiar bump of reflectance in the deep red/infrared region (which has some practical applications). Even though it's easy to make a visual match of it.
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Old 11-16-2017, 05:50 AM
Mythrill Mythrill is offline
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Re: Single Pigment Colors That Cannot Be Mixed

There's also Green Gold (PY 129), which is green in masstone but yellow in undertone. The chroma is not only very hard to match, but the duochromic yellow-green characteristic makes it even harder to copy. Not only that, it's the only green pigment I'm aware of that mixes with Quinacridone Magenta (PR 122) or Pyrrole Red Light (PR 255) and makes yellow, which is otherwise a primary.

In effect, Green Gold is the only pigment I know that allows you to have an RGB (Red-Green-Blue) palette to mix a yellow (albeit a dull one), with:

Titanium White (PW 6)
Ultramarine Blue (PB 29)
Quinacridone Magenta (PR 122) or Pyrrole Red Light (PR 255)
Green Gold (PY 129)

You can manipulate the perception of people to a glowing yellow even further by adding white to the mix and tinting.
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Old 11-16-2017, 02:34 PM
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Re: Single Pigment Colors That Cannot Be Mixed

That which comes to my mind immediately regarding single pigment colors that cannot be mixed, are the primary colors, Cyan, Magenta, and Yellow.

Cyan: PB15
Magenta: PV19
Yellow: PY128

Each of these is a transparent color.

There certainly are other colors, represented by many of the secondaries, (Red, Green, and Blue) whose purity, or chroma cannot be matched by any mixtures of any other two colors. One that comes to mind immediately is Cadmium Orange. Although a rather decent "Orange" can be created by mixing Magenta, and Yellow together, with White,it falls short of having the high degree of chroma that a single-pigment, Cad Orange does.
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Old 11-28-2017, 07:58 PM
contumacious contumacious is offline
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Re: Single Pigment Colors That Cannot Be Mixed

I forgot about this post......setting the "close enough" concept aside, I am still interested in "finding" more single pigment colors that cannot be mixed from a combination of other pigments than what are listed below.

I never did find a published list of all or even some of the single pigments that cannot be duplicated by mixing other pigments, I am going to add them here as I find them, though this might be it. I may put together a combined list quite some time down the road at the bottom, if more of them surface. It appears that there aren't very many out there.

Here are some that I found specifically named on the Gamblin web site as not mixable from other pigments. Perhaps there are others. Feel free to add them as you find them with references if you can.
  • Permanent Orange: (PO 62) A modern high key color with a pure hue and the same masstone (but more transparent) than Cadmium Orange, and it remains brighter in its tint when mixed with white. Painters cannot mix a secondary with the same purity of this pure hue Orange.Pigment: Monoacetolone (PO 62) Vehicle: Alkali refined linseed oil, Lightfastness I, Series 3, SEMI-TRANSPARENT, SDS
  • Cobalt Violet: (PV 14) Deep violet that is cool in its masstone (and less red than Manganese Violet), Cobalt Violet is a pure hue that cannot be mixed from other colors. Although very muted in its tint, it is a marvel as a top coat color. Cobalt Violet greys down considerably when mixed with white.
    Pigment: Cobalt phosphate (PV 14)
    Vehicle: Alkali refined linseed oil
    Lightfastness I, Series 6, SEMI-TRANSPARENT, SDS
  • Cobalt Blue: (PB 28) “True blue,” first manufactured in 1804. This color is well worth the price because of its working properties and unique color, which cannot be mixed. Pigment: Oxides of cobalt & aluminum (PB 28)
    Vehicle: Alkali refined linseed oil
    Lightfastness I, Series 5, SEMI-TRANSPARENT, SDS
And from Patrick1 and Mythrill - somewhat different than my original question, but still applicable - single pigment colors with unique characteristics that cannot be duplicated by mixing other pigments.
  • Green Gold (PY 129)
  • Ultramarine Blue
  • Dioxazine Purple
  • Phthalo Green YS and BS
  • Pyrrole Red
  • Pyrrole Orange
  • Cobalt Teal? (PB28 variation?)
  • Isoindolinone Yellow
  • Nickel Azo Yellow
-----------------------------------------------------------------------

Quote:
Originally Posted by Mythrill
There's also Green Gold (PY 129), which is green in masstone but yellow in undertone. The chroma is not only very hard to match, but the duochromic yellow-green characteristic makes it even harder to copy. Not only that, it's the only green pigment I'm aware of that mixes with Quinacridone Magenta (PR 122) or Pyrrole Red Light (PR 255) and makes yellow, which is otherwise a primary.



Quote:
Originally Posted by Patrick1
I'm not aware of such a list. But just playing with the various pigments available in the art world, you'll find there are many colors which cannot be mixed - either as a unitary (single area of) color, or their idiosyncratic real-world nature (the duo-tone of transparent colors, granulation of some pigments in watercolor, bronzing effect of Phthalos, opacity, tinting strength etc.).

If you look at a good color wheel in which the pigment placements were done by a spectrophotometer, a lot of the colors on the periphery will be unmixable. Some colors that aren't near the periphery on a 2-dimensional color wheel/plot will also be unmixable because they might not be high chroma, but are of high saturation. A few of the non-primary colors which cannot be matched (close enough for practical purposes maybe, but not a match in chroma) :

-Ultramarine Blue
-Dioxazine Purple
-Phthalo Green YS and BS
-Pyrrole Red
-Pyrrole Orange
-Cobalt Teal?
-Isoindolinone Yellow
-Nickel Azo Yellow
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Old 12-05-2017, 06:46 PM
ragtopcircus ragtopcircus is offline
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Re: Single Pigment Colors That Cannot Be Mixed

PO73 Pyrrole Orange, PO62 Benzimidazlone Orange, PY150 Nickel Azo Yellow, and PY129 Green Gold are all to difficult to mix, and not offered in WMO as single pigments.

PO49 Quinacridone Gold is difficult to mix, and no longer available. PO48+PY150 is a common substitute now, but it does not replicate PO49. As a somewhat neutralized color, it's not hard to match the masstone OR undertone, but matching the duochrome characteristics with any one mix is difficult.

Last edited by ragtopcircus : 12-05-2017 at 06:54 PM.
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