View Full Version : dioxazine purple

07-14-2001, 01:28 PM
I use dioxazine purple in my pallette a lot, but have noticed over the years that any painting which uses diox on the last layer wears very badly, suffering loss of pigment and scratches. Also, acrylics are usually waterproof when dry, but if I run a damp cloth over the diox area, it comes off on the cloth, and leaves a scar!

I just bought a new brand,(I was using Liquitex Basic), but as this is a problem that only shows up after time I was wondering if any of you had experienced the same thing ... Especially if this is a characteristic of diox and not just of the basics ...

Also, in regards to purple, I find it nearly impossible to satisfactorily mix from the primaries in acrylic. I buy diox and deep purple to fill that section of my pallette ... do you mix your purples? if so, what brands and colors ?

Wally's Mom
07-14-2001, 02:44 PM
I remember reading somewhere (here on another thread, or somewhere else, I don't know) that diox purple (regardless of the brand) is the one acrylic that is not waterproof when dry. The diox purple I have is also Basics, so I have no experience with other brands to tell you about.

07-14-2001, 03:18 PM
Jheinrich, which primary colors are you using?
Try using a more magenta-ish red. This will give you far cleaner purples. And you will still be able to mix pretty good reds and oranges with it.
Quinacridone magenta (PR 122) is often considered the true primary color (instead of red). If it's too blue-ish, and you want to mix cleaner reds and oranges, you'll probably want something a bit closer to red. But if you want a really clean purple, nothing will match diox. purple straight from the tube...from a quality brand like Golden.


07-14-2001, 04:56 PM
Hi Jeanette, I only read about the problem of Dioxazine Purple not being waterproof recently and it's the first time I have ever heard of this problem with acrylics; I have an old tube of this colour that I rarely use and it is perfectly waterproof when dry so it may only be a problem with the brand you were using, who made it? It's just a guess but it might mean the colour is underbound, i.e. with too little acrylic medium, which would imply it has more pigment than you would typically find which is a good thing :)

When you say "suffering loss of pigment" is that just from abrasion or is the pigment fading in areas?

I favour subdued colours on the whole and I almost always mix my secondaries but you can mix clean, intense violets quite easily given a careful choice of the red and blue - remember both should be violet-biased. Ultramarine Blue is the most common blue recommended as a starting point for mixing clean violets but Cobalt Blue Deep is also superb, although it is much more expensive. For the red, any of the following will yield good results, depending on the specific hue and value you are aiming for (these are in approximate order from least to most violet):
Pyrrole Red, PR254;
Naphthol Carbamide (commonly called Naphthol Crimson) PR170;
Anthraquinoid Red, PR177;
Quinacridone Carmine, PR N/A;
Quinacridone Red/Violet, PV19;
Quinacridone Magenta, PR122.

If you want to stick to single-pigment violets, you might also like to take a look at Ultramarine Violet, PV15. This is probably the best of the blue-violet pigments available today and Winsor & Newton's may be the most useful as it is lighter in value and the most saturated. There are a number of less-saturated single-pigment violets available too but I would prefer to just mix these hues.

There are any number of subdued violets you can mix from common palette colours, if you want any suggestions just give me a shout.

Hope this helps,

07-14-2001, 06:43 PM
Hey Einion, which blues are better for mixing violets/purples: ultramarine blue, cobalt blue deep, or phthalo blue red shade? The reason I ask is because in many places, inculding Golden's website, I read that you'll get cleaner mixes using transparent synthetic colors (all else being equal). Now phthalo blue RS is not as violet as cobalt or ultramarine, but is is synthetic, so it makes me wonder if, it would make better violets than cobalt or ultramarine. I had a tube of Winsor & Newton Griffin alkyd paint in "magenta" color and it was a mixture of PV 19, plus phthalo blue (I believe it was RS). Now if they chose phthalo blue RS rather than ultramarine,
you'd wonder if it's because it gives cleaner violets. But I would still think that ultramarine, despite not being synthetic, would mix cleaner violets and purples.

Another question: why are two diferent colors (quinacridone red and quin. violet) both made with PV 19 pigemnt? Is it variations of the same pigment? (Just like you get ultramarine blue and ultramarine blue deep from the same PB 29 pigment?) The 'quinacridone violet' version of PV 19 looks even more violet than PR 122 (magenta).

As to ultramarine violet, it's a color I want to try, but looking at my Golden hand-painted color chart, ultra. violet seems less clean and intense than diox. purple...it looks more greyish.
I know its supposed to be a lighter value, but it seems noticably less intense and clean. What gives?


07-15-2001, 01:48 PM
If you're having trouble with dioxazine resolubility, you might try isolating it by spot-varnishing your purple with some matte medium pefore proceeding to other colors.

Incidentally, I find I get some incredibly intense reds and oranges by mixing quinacridone violet and yellow medium hansa. This mix looks really good airbrushed.

07-15-2001, 11:47 PM
Hi Patrick, I would think that as a general rule Ultramarine Blue would mix better violets than either Cobalt Blue Deep or Phthalocyanine Blue RS because it is usually the most violet-biased blue. However my research has shown that the specific hue of a given colour can vary quite a bit from various manufacturers so without specific samples it's impossible to be definite (of the three I only use Ultramarine). The Phthalocyanine Blue RS from Winsor & Newton is supposed to be the most violet-biased of any manufacturer's (making the pairing of the RS and GS from them most useful on the palette) but I think it still falls short of the violet reflectance of a typical Ultramarine.

I've read that about transparent synthetics mixing cleaner violets but this might be an interpretation based on the transparency of the resulting violet and not necessarily the specific hue but I'm willing to be proved wrong. From a chromatic point of view the most violet-biased blue should mix the cleanest violet but it also depends on the how 'clean' the colour is; all colours reflect other spectra in addition to their basic hue position and put simply the one that predominates gives the colour its bias. The transparent synthetics pigments could be inherently cleaner as a class but I don't know if this is correct.

With regard to the Griffin alkyd you mention, I wouldn't like to second-guess the colourmen in Winsor & Newton because despite my affection for their acrylics they have made some very odd decisions for their ranges. The best example of this is Permanent Alizarin Crimson with different pigments used for their oil, acrylic and watercolour ranges: in oils it's Anthraquinoid Red and why they didn't just offer this apparently superb single pigment for the other two instead of mixes is beyond me.

As for Quinacridone Red and Violet both having the same number, it's probably because they are the same chemically, but two slightly different forms of the molecule. I would think something like the system used now for the various phthalocyanines (PB15:1, 3, 6 etc.) would be a good idea to distinguish them but there may be a reason for it as with PBr7 being used for so many earth colours.

Hand-painted charts are obviously a great idea, and in the case of Golden's if the Ultramarine Violet looks duller than Dioxazine Purple then from them it must be: other manufacturers' versions are not exactly the same. By reputation it probably doesn't look as intense as Dioxazine Purple but it from what I've read it shouldn't look "greyish" by any means. Apart from that offered by W & N, the Daniel Smith and Rembrandt versions might be worth a look, theirs are apparently slightly darker and redder in hue.


07-17-2001, 06:21 PM

Hi, and welcome to WC!!

Have you tried mixing Cobalt Blue with Alizarin Crimson? Makes a beautiful violet.

Diox. is very deep and rich, and depending on the brands/pigments creating a mixed equivalent is difficult.

Have fun experimenting!


07-18-2001, 10:46 AM
wow. I'm learning so much, here, thank you all for your thoughtful replies.

I have about a million questions :)

mostly to Einion- I don't understand what the numbers you were referring to mean-- PB15: 1, 3, 6 etc ... I see them on my tubes, but would you explain a bit about what they stand for?

when I said 'suffering loss of pigment' I meant abrasion ... getting scuffed up from being stored next to other paintings, the only two it's ever happened to were both primarily diox.

I figured out why my violets weren't mixing well, I was using a yellowish light opaque red. By the time I expanded my pallette into other reds, I had given up mixing violets ... I'm back at it now. Red based transparent blues and blue based transparent reds- I'm there :D Aquamarine Violet, I'll check it out.

I'm experimenting with another diox at the moment, also, I'll let you know if it's waterproof.

artistry: it's me, jnet11, I changed my handle so that I was using my real name. :D hi again.

07-18-2001, 11:33 PM
Alizarin Crimson Artistry? "Unlightfast, unlightfast!" he cries! ;)

First off Jeanette, that abrasion problem with your Dioxazine Purple certainly sounds like the paint has too little binder. Even apart from this problem I would strongly advise varnishing your paintings to protect them from humidity and dust. There are a number of varnishes intended for acrylics that are completely removable without disturbing the paint underneath.

The numbers I used and that you have noticed on your tubes are the Colour Index Numbers that refer to the specific pigment used in the paint - think of them as codes so you can look for them instead of relying on the name on the tube. PB stands for Pigment Blue, PR for Pigment Red and so on - Y for yellow, Br for brown, Bk for black, V for violet, G for green and O for orange. This numbering system, and the names that go along with them, are part of ASTM (American Society of Testing and Materials) industry guidelines for paint to help you know what you're paying for, up to a point. It's not too hard to learn the dozen to two-dozen numbers that you use in your chosen palette and keep these in mind if you are trying a new brand.

I am careful to quote them when I want to be specific about pigments, as there are so many proprietary and traditional names in use for paints - you will often see a name on the tube that should refer to a pigment, not just a 'colour', when in fact there is something completely different in the tube. Naples Yellow is a good example of this: today this is almost never the real single-pigment colour except in oils, but instead a proprietary mix (usually of white, yellow and a red earth). Of course any decent manufacturer that offers a mix for this will list the colours on the label so you can see what they used and mix it yourself if you want! I have mentioned this often to my oil-painting friends with regard to other colours like Sepia, Paynes Grey, Indigo, Hooker's Green, Antwerp Blue etc. all of which are simple mixes these days.

You can use knowledge of these numbers to your advantage in other ways: for example I was looking for the darkest pigment black for my work, which I knew by reputation to be Carbon Black, PBk7 (Pigment Black 7) and I was very pleased to see this number on a tube of Maimeri Brera acrylic under the name Ivory Black. These days true Ivory Black is not made any more of course, and is usually Bone Black, PBk9, masquerading under the older, more romantic name (Bone Black doesn't have quite the same ring does it?!) Anyway, PBk7 is as intense and staining as I had heard and makes a good pair with my Liquitex PBk9 which is warmer, much weaker in tinting strength and therefore more versatile in mixes. Incidentally you will often see the name Lamp Black (which is actually PBk6) these days when in fact it is Carbon Black in the tube, possibly because Lamp Black can be slightly oily so it is not easily made into a water-based paint.

The ASTM perform lightfastness tests on pigments in different mediums and they publish these tests which give you a good idea of which pigments are reliable in your chosen medium, obviously a good thing. One reason this is important is that quite a number of pigments are more reliable in one medium than in another - linseed oil appears to offer the best protection to pigment particles on the whole, so oils often have a higher lightfastness rating than the same colour in acrylics (this is even more evident when compared to watercolours). These ratings are often quoted on labels and although they are not perfect they are a good starting point; sometimes you can trust the manufacturer's rating when it says it is higher than you might have read for a given colour.

Hope this isn't too wordy to be helpful :D


07-18-2001, 11:35 PM
I did some research over the weekend and Ultramarine Violet, despite appearances, should be far higher in chroma than Dioxazine Purple (2.5 v. only 0.5!) and is a great deal more lightfast. Given that and the latter's highly staining nature it makes Ultramarine Violet sound even more attractive!

Also, I mentioned about Anthraquinoid Red above and I found that Permanent Madder in the Rembrandt Acrylic range is actually this colour - one would never know this is they didn't list the pigments on their very nice website. This is a prime example of why I say if a manufacturer does not print these numbers on their paints (like Rowney Cryla) don't touch them.


07-19-2001, 01:45 AM
I have a color wheel which shows that diox. purple and ultra. violet are very close in relative hue, but ultra violet is closer to the outer edge of the circle, meaning higher chroma.

But as I said before, the ultra. violet does indeed look clearly less saturated, less intense, kinda greyish compared to diox. I doubt that Goldn's ultra. violet formulation is flawed...I'd expect it to be at least above-average. But I will check out this color in some other brands when I have time.

I was thinking: can it be that darker colors, even if they are very intense (like diox. purple) recieve a 'penalty' in their chroma value due to the fact that their masstone appears almost black? This is the only way I can think of that explains this. Example:

In my Liquitex color guide booklet, it lists diox. purple as having a chroma of 1. Yet it also lists raw umber and burnt umber as also having a choma of 1! We all know that diox. purple is a far purer hue than any brown.

So I think that due to its darkness it recieved the low chroma value, even though it's a pure, intense color. What do you think?

07-19-2001, 04:50 PM
According to the source I found the chroma information on, <A HREF=http://www.goldenpaints.com/dioxpulp.htm>DP</A> and <A HREF=http://www.goldenpaints.com/ultvio.htm>UV</A> should have the precisely the same hue angle. Click on the links, you might be surprised at the source of this information! FWIW Handprint's data supports this although it is obviously not for these specific examples.

I think your problem might be in confusing saturation and chroma, they are not precisely the same thing. Example: Cobalt Blue has a higher chroma (approx. 11) than Phthalocyanine Blue (approx. 4), which would you consider more saturated? Here's one definition I found that might help: <i>Often confused with saturation, chroma has more to do with the sharp brightness of a color rather than the general fullness of it.</i>

There is no penalty, per se, with regard to value when considering chroma. Example: Cerulean Blue, value about 4, has a chroma of approx. 8 while Cobalt Blue has a value of around 3 and a chroma of 11. These determinations aren't done subjectively for obvious reasons, they use something like reflectance spectrometers to measure these values.

With regard to "purity" of violet v. browns, while the Liquitex Munsell chroma numbers are rounded up/down to whole figures it is essentially correct, Dioxazine Purple is a low-chroma pigment. Also according to Golden, Burnt Umber's chroma is 1.0 and Raw Umber's is 1.3 so in fact they are both higher in chroma that DP!


07-20-2001, 01:20 AM
Einion, thanks for that info regarding chroma and saturation. I always heard about saturation and thought it was another word for chroma. So let me get this straight:

chroma is the sharp brightness or cleanliness or purity of a color (as I always thought)

saturation is the richness or fullness or "heaviness"

So I would think phthalo blue is more suturated than cobalt blue( even though it's lower chroma), and likewise diox purple more saturated than ultra violet (even though it's lower chroma).

That Handprint site sas TONS of color theory info. I printed much of the color theory info, and that excellent color wheel long ago. It cost me nothing, and it's far more comlplete (in terms of the amount of colors on it) than the Quiller color wheel which I paid $12 for.

07-20-2001, 06:41 PM
Yeah the Handprint site is simply amazing. I still can't get over the fact that it's all free (and no banner ads!!) I reckon it would take a couple of months to go through the whole thing and extract all the gems. What is perhaps even more impressive is that it appears to be the work of only one person.

It has made me consider trying watercolours again more than once just to take better advantage of it!


07-22-2001, 10:18 AM
diox purple is a light, fluffy pigment which is very hard to control. my guess is that the substandard vehicle in the liquitex basic paint did an inadequate job of binding the pigment, which caused it to rub off. some student-grade pthalos have the same problem.

ultramarine violet is my personal purple choice, but not because it is more reliable, but simply beacuse it is subtler. i've had little success mixing other colors with dioxazine purple since it has such radical staining power. i use ultramarine violet as my "black" when painting in acrylics since black acrylics tend to look so dead.

08-01-2001, 05:44 PM
Dioxazine Purple is a very tiny pigment. Therefore it can be loaded up in paints readily, and why most of the time it's really very dark. It's also one of the factors which makes it more susceptable to lifting when rubbed. Certain varieties of this pigment have problems with bleeding (put a swatch of Titanium WHite over the full strength color and see a halo emerge though the white).

As was mentioned up above, weak binding is a big part of the problem, and adding some gel or medium (I suggest gloss to keep the color cleaner and brighter), or apply a gloss medium over the artwork when complete.

The issue of chroma and ratings of it are based on thick, masstone readings. This skews the results and it therefore reads as almost a black. However, add some medium or make a wash, and you'll discover how intense this pigment is.

It is at best a lightfastness II color, and you can make a good subsitute with Phthalo Blue Red Shade and Quinacridone Magenta.

08-01-2001, 08:22 PM
Originally posted by Einion
What is perhaps even more impressive is that it appears to be the work of only one person.

Yes, it is. Once upon a time I emailed him that he should finish up the techniques section and put everything into a book, because I think it would be the must-have reference book for every watercolor painter (although painters in every medium can benefit from his color information). He's not doing it for money, though, but just for the love of the medium.


08-01-2001, 10:49 PM
Originally posted by VictoriaS
...he should finish up the techniques section and put everything into a book, because I think it would be the must-have reference book for every watercolor painter...
Thanks for the info Victoria, that would be a must-have - I'd buy one!