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Einion
11-30-2004, 02:57 AM
Patrick (Domer) brought this up in another thread and I think it's interesting enough to discuss on its own. Numerous examples exist of paints, single-pigment colours and mixes, that don't mix quite as one would expect from casually looking at the basic appearance straight from the tube (the masstone or toptone). Most people who have used paint for a while will be familiar with this even if they don't realise it, we've all seen at some point a mixture that looks like another colour yet just doesn't behave the same way when brushed out thinly or mixed with other colours. The most common being mixtures compared to a single-pigment colour that looks the same.

There are a host of reasons for this effect I suspect but I think variations in opacity and undercolour are likely to be the two major factors. Another will be subtle a difference in their reflectance spectra - two colours can appear indistinguishable but actually have quite different reflectances, an effect called metamerism.

To get to specific examples, some of the simplest are tints; if we take a handful of colours and mix them with white we see there are some striking contrasts. Cobalt Blue mixes pretty 'linearly' with white, the tints basically following a straight line (i.e. the hue doesn't alter) as you add more white. Phthalo Blue GS on the other hand has a distinctly cyan undercolour and this shows up in its tints as well, so as you add white the hue shifts noticeably in the direction of cyan. Another difference between these two is that the tints of Cobalt Blue are relatively dull, while those of Phthalo Blue GS are much more vivid, the phthalo colours being members of a rare group of paints where the chroma increases as you add white (up to a certain point) and consequently remains higher for a given value. To pick two colours that look very similar, a common colour used in Cadmium Red Hues is a naphthol red, PR112, and superficially it looks very close to a medium shade of Cad Red. But if you check the undercolours you can see that Cadmium Red's looks much like its masstone (sometimes shows a small move to orange), while PR112 shifts in the direction of magenta; when you add white the difference is more obvious, Cadmium Red's tints keeping to about the same hue, PR112's markedly more magenta. As with the previous example the tints of the first colour are relatively dull, while those of the latter are noticeably higher in chroma. See note*.

Another one I'd like to mention here is something Bill (WFMartin) has mentioned a couple of times, the unusual tint he observed in his Grumbacher Cadmium Orange, which were noticeably pink (instead of the roughly salmon-through-to-peach colours one would expect). At the time he mentioned this first I had one Cadmium Orange - a middle orange in comparison to the more red-orange of the Grumbacher colour - and it didn't share this characteristic, which just goes to show how variable a given colour can be on more than one level. I have a Perinone Orange in acrylics now and when I was testing it I found its tints are very evidently pinker and pinker as you add more white, so the effect is not isolated to just Cad Orange either.

Any of us can examine this sort of thing by just picking a tube colour that one could mix from others - e.g. Cobalt Blue, Cerulean Blue, the siennas, Chromium Oxide Green. When you have a good match compare the imitation with the real thing in tints and mixtures with other colours - add yellows to the blues to compare their mixed greens for instance. Bill mentioned this in relation to testing his mixed imitation with Cadmium Orange itself and their completely different tints.

As Patrick mentioned in the other thread the most common class of mixtures that don't follow a straight line between the two starting colours are greens - if you plot the positions of the yellow and blue accurately on a colour wheel and draw a line between them it's instantly obvious that what you actually get is very different. Another type of colour pairing that doesn't follow a straight line when plotted in this way are certain complementary pairs; there are many colours that mix good neutrals with another that is not even remotely opposite in hue. Probably the earliest example of this I learned (with no idea of the significance) is very simple and clear illustrates the principle - the very different earths that mix adequate neutrals with a number of different blues.

It should be evident that all of the points above prove conclusively that any notion of the predictability of paints and how they mix based purely on their colour is simplistic and doesn't reflect their true nature, so be wary of any system that claims otherwise ;)

Einion

*In case it escaped notice, the examples in this paragraph are clear illustrations of the fallacy that adding white always cools - while it's very obvious that tints of the naphthol red mentioned are 'cooler', you can see that at best it's an oversimplification by just comparing the tints of a very similar starting colour. But a complete disproof is also right there - cyan is 'warmer' than blue, hence the tints of Phthalo Blue GS are warmer than the starting colour! So it's actually a little more accurate to say that white cools warms colours and warms cool colours as a general rule of thumb, but there are exceptions, as there are to most 'rules' in colour mixing.

Richard Saylor
11-30-2004, 07:59 PM
It should be evident that all of the points above prove conclusively that any notion of the predictability of paints and how they mix based purely on their colour is simplistic and doesn't reflect their true nature, so be wary of any system that claims otherwise ;)
It is unfortunate that such an obvious truth can become a hot potato at WC.

Einion
11-30-2004, 08:43 PM
So true.

Einion

Brian Firth
12-01-2004, 01:18 AM
One of the craziest unpredictable colors I have used is Green Gold Azomethine (PY129). It appears green in masstone but when you mix it with reds you get some nice oranges. Then if you mix it with a cool yellow you get a nice light lime green. It's a great mixing color that gives all kinds of unique hues.

WFMartin
12-02-2004, 01:23 AM
Einion,

You make some excellent points here, and I certainly agree with your assessment of this phenomenon, that occurs when mixing colors, or white with colors.

From purely an academic standpoint, I'd sometime like to find explanations for some of those overtone phenomena, for no other reason than to satisfy my own curiosity regarding just why that happens.

Perhaps, then, the results could be made to be a little more predictable, and therefore a bit more "teachable" with it comes to explaining just what to expect, and why, to beginners. For now, all I can ever explain to others is that it happens, and is quite unpredictable regarding in what direction the hue will swing when mixed with white.

Always, the "teacher" in me, coming to the fore. :D

Bill

Einion
12-02-2004, 10:37 PM
From purely an academic standpoint, I'd sometime like to find explanations for some of those overtone phenomena, for no other reason than to satisfy my own curiosity regarding just why that happens.
Me too. The physical traits that affect it - pigment particle size(s), transparency and undercolour/masstone differences I think are almost certainly the factors of note - and these can be so variable, along with any differences that might pertain to diff. media, I suspect we'll never get to an absolutely concrete understanding except with specific paints from a specific maker. Thank goodness the bulk of paint mixes are a little more consistent eh?

Perhaps, then, the results could be made to be a little more predictable, and therefore a bit more "teachable" with it comes to explaining just what to expect, and why, to beginners. For now, all I can ever explain to others is that it happens, and is quite unpredictable regarding in what direction the hue will swing when mixed with white.
Yep, know just what you mean :) For now at least we can use the tried-and-trusted approach of passing on the oddballs we know from practical experience and from reading but the variability of the same colour from one paint to another makes this one of those things I suspect will have to remain in the "this may happen..." category!

Einion

WFMartin
12-03-2004, 11:50 AM
Einion,

How right you are!!

Bill

Patrick1
12-04-2004, 03:51 AM
Cerulean blue has a sharp peak at the far red end. Does this mean that it is surprisingly good (considering it's somewhat dull colour) at mixing violets with magenta or rose?

Also, anyone know which of Golden's cerulean blues is the 'common' cerulean blue...the cerulean blue that is implied whenever some says 'cerulean blue':

'Cerulean Blue Chromium' PB36:1 or
'Cerulean Blue Deep' PB36

They don't have PB35...maybe it's the 'regular' cerulean blue.

Richard Saylor
12-04-2004, 07:44 PM
Cerulean blue has a sharp peak at the far red end. Does this mean that it is surprisingly good (considering it's somewhat dull colour) at mixing violets with magenta or rose?
I don't know about cerulean, but cobalt blue also has a peak at the red end, and it makes gorgeous violets with quinacridone rose. In fact, I'm almost certain it makes higher chroma violets than ultramarine blue. I suppose this is sort of paradoxical, since ultramarine is closer to rose on the color wheel.

Patrick1
12-11-2004, 08:48 AM
Somewhat related theory question...something I've been wondering about for a long time. Say you wanted a single violet pigment with the highest chroma possible. Would that be...

1) one with maximum reflectance at the far violet end and nowhere else?

2) as above, but with reflectance extending further into the blues and also some reflectance in the far red regions?...it would be the same hue but lighter

The first would be more spectrally pure but very dark. The second would be less spectrally pure but lighter...probably easier to see its violet colour. Which one would be higher chroma?

FriendCarol
12-11-2004, 09:57 AM
Somewhat related theory question...something I've been wondering about for a long time. Say you wanted a single violet pigment with the highest chroma possible...
I'm not sure about the answer in the abstract (and perhaps it depends somewhat on what you plan to do with your single pigment), but since I had various violets in my initial eBay purchase, I read Handprint.com carefully on this specific hue before giving away my "extras": Dioxazine (Winsor violet) was a more definite, brighter, purer color than the ultramarines and others.

Dioxazine has a chroma curve very much like the thalo's -- add very little water for maximum chroma (with watercolor binder, obviously!). Disclaimer, while I'm at it: I do NOT think a good approach to painting is to attempt to obtain maximum chroma for every pigment or mixture used. (I say this because that's what McEvoy seems to be suggesting! Any novices here, don't be misled.) :)

Mikey
12-14-2004, 08:43 AM
Cerulean blue has a sharp peak at the far red end. Does this mean that it is surprisingly good (considering it's somewhat dull colour) at mixing violets with magenta or rose?

Also, anyone know which of Golden's cerulean blues is the 'common' cerulean blue...the cerulean blue that is implied whenever some says 'cerulean blue':

'Cerulean Blue Chromium' PB36:1 or
'Cerulean Blue Deep' PB36

They don't have PB35...maybe it's the 'regular' cerulean blue.

I have Golden Cerulean Blue deep, which I think is darker than the normal pigment. I also have the Michael Harding Cerulean Blue, which is PB35 and this is lighter. I prefer the lighter pigment as it seems preferable not to have to mix with white, or at least keep that to a minimum.

Mikey

Mikey
12-14-2004, 08:56 AM
Einion, I'm not sure where to post this, but thought here rather than resurrect an old thread. I took your advice and bought the Trans red Oxide. It is a nice clean mixer as would be expected, good for grounds, and the surprise it makes a very deep, solid black with Ultramarine. Although we might expect the black, I guess the strength of the pigment gives it extra measure.

I've also bought Magneta and Unbleached Titanium Oxide. An experiment with the Magenta and Yellow Ochre proved the usefulness of that combination for flesh tones. I was always pleased with Unbleached Titanium using Golden Acrylics, especially for flesh tones. Genuine Naples Yellow Light is an unexpected pleasure straight from the tube being so light, it also makes very intense light colours without any white.

I have Michael Harding oils, except for the Cobalt Blue and Napthol Red, which are Old Holland.

Mikey

Patrick1
12-18-2004, 03:27 PM
Einion, I'm not sure where to post this, but thought here rather than resurrect an old thread. I took your advice and bought the Trans red Oxide. It is a nice clean mixer as would be expected, good for grounds, and the surprise it makes a very deep, solid black with Ultramarine.
That must be a delicious black / near-black...probably much like the kitty in your signature.

Mikey
12-18-2004, 04:18 PM
That must be a delicious black / near-black...probably much like the kitty in your signature.

It is delicious and with a small amount of turps like black acrylic ink. What did surprise me was the opacity and covering power from two transparent pigments.

Mikey

FriendCarol
12-21-2004, 08:01 AM
It is delicious and with a small amount of turps like black acrylic ink. What did surprise me was the opacity and covering power from two transparent pigments.
Yes, as I noted in an earlier Watercolor forum thread, combining granular (or flocculating) pigments cuts down considerably on the transparency of mixtures made from them. Ultramarine and your oxide (I assume that's what some manufacturers use to make some earth colors -- granular ones) would therefore, both being granular, produce quite an opaque mix even though individually they are seen as transparent.

This makes sense to me intuitively, sort of like mixing screens of different sizes (meshes?): I think of the dried solution of the pigments as being like a screen -- you can certainly see through a screen, but put two or three together and they're a lot harder to see past, particularly if the screens are offset or in different sizes. :)

Mikey
12-21-2004, 08:13 AM
Yes, as I noted in an earlier Watercolor forum thread, combining granular (or flocculating) pigments cuts down considerably on the transparency of mixtures made from them. Ultramarine and your oxide (I assume that's what some manufacturers use to make some earth colors -- granular ones) would therefore, both being granular, produce quite an opaque mix even though individually they are seen as transparent.

This makes sense to me intuitively, sort of like mixing screens of different sizes (meshes?): I think of the dried solution of the pigments as being like a screen -- you can certainly see through a screen, but put two or three together and they're a lot harder to see past, particularly if the screens are offset or in different sizes. :)

Yes, that would seem to make sense, although I think you'd find that opaque Red Oxide makes for a rather less black. I could try that with acrylics. However, the Trans Red Oxide very often makes a mix which is too black for practical use. BTW I'm using high pigment loaded paints, both oil and acrylics.

Mikey

creative soul
01-01-2005, 02:24 PM
i've noticed that two bright colors, pthalo green and dioxazine purple, when mixed together give a lovely dull blackish-blue.

Mikey
01-01-2005, 02:36 PM
i've noticed that two bright colors, pthalo green and dioxazine purple, when mixed together give a lovely dull blackish-blue.

I've never tried it, but a nice and useful colour I bet. Who's ever tried mixing Chrome Green Oxide with Violet? Yuk!!!

Mikey

A Few Pigments
01-04-2005, 02:58 AM
I just stick to single pigments…but they come off with a little turps.

Patrick1
01-04-2005, 09:39 AM
Who's ever tried mixing Chrome Green Oxide with Violet? Yuk!!!

I've never had chromium oxide green, but when I need a greyish blue, my favorite method is to mix a violet with a green. (I much prefer this to taking a blue and greying it down with it's complement). Adding white to the mix reveals the beautiful smokey blue.

killerkatt
01-04-2005, 10:12 AM
I sometimes think of the colors I use as opaque vs transparent.
Opaques seem to almost always mix in a linear way, whereas the more transparent a colors have different shifting undertones.

killerkatt
01-04-2005, 10:16 AM
i've noticed that two bright colors, pthalo green and dioxazine purple, when mixed together give a lovely dull blackish-blue.
I bought a half pint once of Payne's gray from a certain manufacturer, and it seemed to me not to be a true Payne's, but was just a mix of dioxazine and pthalo green.

Bill Foehringer
01-12-2005, 04:22 PM
Are spectra available from paint manufacturers? Not that spectra alone will precisely predict how a substance will appear to shed photons when mixed with other substances. Each substance would reflect certain wavelengths from the other pigments with different efficiencies depending on several variables. What is the relative amount of each isomer of each pigment molecule that is produced by different production methods? Too many other variables. Long ago I was a chem. major. I'm not writing from any experience with pigments themselves. Even a physical science like chemistry has a component of art and it shows up in the formulations of artist's colors. Besides, trial and error is fun even for chemists. BillF

Einion
01-13-2005, 09:24 PM
Are spectra available from paint manufacturers?
Hi Bill, basically no. I can only remember seeing a couple over the years and one of those was for a neutral grey to show the flat reflectance profile so it wasn't very exciting to look at! :D

I'm sure that most of the big ones will have them as part and parcel of their internal testing procedures, at least a couple certainly do, but they are not routinely included in their publications and on their websites. Part of this may be because it is perceived that they would be of limited, if any, use to their customers and part could be due to protection of what they see as proprietary info. You can understand the reasoning in the second case, it wouldn't do to have it made obvious how similar certain colours are from one maker to another, even in what amounts to a superficial way.

Not that spectra alone will precisely predict how a substance will appear to shed photons when mixed with other substances.
That's correct. We've talked about this a few times over the past years and most of the regulars here agree that this is the case and there are some clear examples to support the idea if anyone were in doubt - the simplest being colours with uniform reflectance interacting with others in a way that doesn't appear to make sense.

Basically it comes down to paints being frequently unpredictable and they can be idiosyncratic in how they react in mixes with others, appear when brush out thinly/glazed etc.

Einion

sarahbellum
02-06-2005, 06:54 PM
About the fact that cerulean and phthalo blues make better purples than ultramarine does even though ultramarine is theoretically closer to crimson on the color wheel: if you take cyan and magenta and yellow as your primaries, rather than red, blue, and yellow, you'll realize why. Ultramarine is not a primary in an additive scheme, but phthalo is (or at least closer to one)--thus phthalo gives a cleaner, less neutralized mix.

Richard Saylor
02-06-2005, 09:19 PM
About the fact that cerulean and phthalo blues make better purples than ultramarine does even though ultramarine is theoretically closer to crimson on the color wheel: if you take cyan and magenta and yellow as your primaries, rather than red, blue, and yellow, you'll realize why. Ultramarine is not a primary in an additive scheme, but phthalo is (or at least closer to one)--thus phthalo gives a cleaner, less neutralized mix.

The usual additive primaries are red, green, and blue. Cyan, magenta, and yellow are subtractive primaries.

Pthalo blue green shade is closer to a primary cyan than pthalo blue red shade. Therefore, according to your argument, pthalo blue gs should make better purples than pthalo blue rs. It doesn't work that way. It would also follow from your reasoning that magenta and yellow should give better oranges than, say, naphthol red and yellow, since magenta is a primary, not naphthol. I really think you are mistaken.

drollere
03-13-2005, 03:19 AM
Einion,

You make some excellent points here, and I certainly agree with your assessment of this phenomenon, that occurs when mixing colors, or white with colors.

From purely an academic standpoint, I'd sometime like to find explanations for some of those overtone phenomena, for no other reason than to satisfy my own curiosity regarding just why that happens.

i think einion made a good overview of some of the phenomena. i posted an explanation in part under cunparis' thread on tints of orange, won't repeat it here.

in schema the problem comes down to this.

students need to start with the understanding that what they mix are substances, usually paints. "colors" are sensations in the mind that can be induced by paints viewed in normal situations, as by many other things in life. so by titling the thread "colours that give unexpected mixing results," einion has perpetuated rather than confronted the basic problem.

but he gets right back on track by pointing to some material qualities of the substances, and of these, particle size and particle size distribution, refractive index, tinting strength, lightfastness in vehicle on support, reflectance profile (color appearance and mixing behavior) are most important. (others are media specific, such as specific gravity for watercolor painters, or oil index for oil painters.)

to martin's point about teaching: teach it. show them the difference in tinting strength between phthalo blue and ultramarine, then show them the difference in tinting strength across different brands of paint. same for oil index, etc. show them the difference between a tint produced by a white mixture and a tint produced by glazing over a white ground. explain all these things to them. show them the physical qualities of the materials they build with.

artists have somehow gotten snookered by the "color theory" lobby into teaching completely fatuous, bogus, meretricious, useless "color facts" to students who then flail around with material substances as if they were born blind, because they look only at the single quality of the substances that is least dependent on them: the interior skull buzzing we call "color."

they then erect arbitrary, ritualistic geometric icons as "ways to help students think about color," driving them ever farther into their interior skull buzzing and ever farther away from looking at what happens to paint.

anyway, back to the thread: what is "unexpected" about *paint* mixtures is that they don't conform to an expectation, and the best way to dispel the expectation is to get in there and mix. so the final piece here is just teaching students to mix and paint, mix and paint, and let the experience take care of the misconceptions.

what is unexpected about *color* mixtures is that anyone would believe you could draw a circle, make a triangle inside it, and with this dumbed down color icon explain the multidimensional, multicontextual, vibrant, complex and substance dependent process of mixing paints.

drollere
03-13-2005, 03:28 AM
Pthalo blue green shade is closer to a primary cyan than pthalo blue red shade. Therefore, according to your argument, pthalo blue gs should make better purples than pthalo blue rs. It doesn't work that way. It would also follow from your reasoning that magenta and yellow should give better oranges than, say, naphthol red and yellow, since magenta is a primary, not naphthol. I really think you are mistaken.

it's amazing how a completely useless "primary" color dogma has usurped a completely simple color wheel rule: all else equal, the farther apart two paints are on the color wheel, the duller their mixture will be.

it doesn't matter which two paints, or where they are on the color wheel.

forget primary colors. just forget them. they don't exist, and never did. they are completely useless ideas.

just read the color wheel like a clock face, and count the numbers between cyan and magenta. ok, now count the numbers between ultramarine and magenta. which two paints are closer together?

ok, well, mix the two pairs of paints and compare the results. what do you see?

if students were taught in this way for one week, they would have one opinion about color theory: "why bother"?

Einion
03-13-2005, 04:18 AM
Hey Bruce, good to see your posts.

artists have somehow gotten snookered by the "color theory" lobby into teaching completely fatuous, bogus, meretricious, useless "color facts" to students who then flail around with material substances as if they were born blind, because they look only at the single quality of the substances that is least dependent on them: the interior skull buzzing we call "color."
http://www.wetcanvas.com/Community/images/20-Aug-2003/3842-thumbsup.gif

what is unexpected about *color* mixtures is that anyone would believe you could draw a circle, make a triangle inside it, and with this dumbed down color icon explain the multidimensional, multicontextual, vibrant, complex and substance dependent process of mixing paints.
What is astounding to me is that one could have weeks-long debates and fail to get across the fact that colour can't be accurately described with a two-dimensional model, much less one that is perfectly circular, and then try to arrange paints equidistant around it :D

it's amazing how a completely useless "primary" color dogma has usurped a completely simple color wheel rule: all else equal, the farther apart two paints are on the color wheel, the duller their mixture will be.
While this is true I do think there's a place for primary colour as a basic idea for painters. I know it's all to easy to get drawn down a path that leads to nothing very useful but from discussing colour ideas and mixing over the years here and elsewhere I can see the benefit to many people in having them as cornerstones in a working palette. As well as this the different gamuts of various choices are interesting and can make for some good work from those who can handle the mixing chore.

if students were taught in this way for one week, they would have one opinion about color theory: "why bother"?
LOL

Einion

Richard Saylor
03-13-2005, 02:36 PM
.....I do think there's a place for primary colour as a basic idea for painters.
Even Bruce uses the "p" word a lot at the Handprint site ;) , but he has a tendency to enclose it in parentheses, which I suppose serves to distinguish his usage of the term from the common misconceptions.

FriendCarol
03-13-2005, 03:37 PM
I should be painting right now, but a few more minutes won't hurt...

It seems to me that color theory has been quite useful to me -- but I've learned to add in dimensions other than hue as my 'theory' becomes more sophisticated. I say this because my 'complete' palette consists of about 21 colors/pigment mixtures (things in tubes) at this point -- without any theory to guide me, experiencing what's possible could take up all the time I have available!

So, as a w/c painter, I understand hue (chroma, value, etc.), but also learn the characteristics of my pigments (transparency, granulation, tinting strength). From these characteristics, I am able to predict quite well what will happen if I mix certain colors. Then, if I'm planning a palette I haven't used previously (which, btw, usually consists of about 4 colors, but varies between 2 and 7), I do usually make color squares first -- but only for any combinations that happen to be 'new' to me.

If I only had experience to guide me, I hate to think how 'at sea' I would be in trying to put together a palette to achieve certain effects!

So, if someone were teaching me about color (if I went to art school or had a tutor), I would want to be shown a decent 3-dimensional model, just to get the basics (not more than an hour on that!), then I would want to be told which characteristics of pigments were also relevant (another hour or two) with how these affect mixing. Finally, maybe give out a list of pigments with varying characteristics and have me experience for myself how it all works.

That's basically what I did (with Bruce MacEvoy's site) teaching myself, anyway. Actually, the later books (and videos, I assume) by Zoltan Szabo emphasize this approach, too -- he explained characteristics of tube colors, then said how he's going to use them in a painting, then demo'd the painting. Very, very useful approach. :)

But don't give me no theory at all! :( As a tech writer, I learned that 'narrative structure' helps even for the driest material -- it seems to give humans a hook-structure from which to hang facts. Cognitive theorists would phrase it differently, to do with chunking and other memory strategies, I think.

gnu
03-15-2005, 01:24 AM
If you mix burnt umber with Pthalo blue, you get the most gorgeous inky green/blue (indigo), it's very very nice..
I get brown or very deep neutral when mixing with ultramarine, so i didn't expect this lovely reSULT!