RE: archivalness of gum
> If there's no paint > called "indigo" that consists of prussian blue and > quinacridone red, then the statement not only isn't "100% > accurate in all cases" but is categorically false. If it is categorically false, it still does not change a bit of the sense that I was trying to say, contextually speaking. > Hue names are useless for gum printing, because they tell you > nothing about the pigments involved; if you don't know and > understand the pigments you're using, you're losing out on > one of the crucial > control variables of gum printing in my experience. So discussing > colors in terms of hue names just confuses and misleads > people, and I can't see any point in it. But again, we were NOT discussing hue names for gum printing. Judy mentioned about that some names are hue names and not pigment, so I just added something casually. Come on, Judy and I have known each other for more than a decade (I haven't met her in person though), so why can't we talk about this things on the list since it is not totally out of topic? Does everything we say has to be technical details on gum printing? And Judy later mentioned that we ran a thread about this many years ago. I remember that too. I remember saying similar things too, but there are many new people on the list, so maybe my background in painting (and the use of real gamboge, for example) might be interesting to others. But that said, I am not going to say that using hue names is totally pointless. A few years someone on the list mentioned that when he print his gum print in monochrome, he didn't use use a black/gray pigment. Instead, he uses indigo for one layer and a brown (I forgot which one) for another layer. It achieves neutral tone but in a more interesting way. Now in my mind, I can visualize the effect a little and found that interesting/beautiful because I have used other colors that way. I am not going to say that since he said indigo and certain brown, his statement was totally pointless because if I tried to dupicate his effect, my indigo would be different from his indigo, and my brown would be different from his brown, etc. etc. The discussion was not about how to duplicate the same thing. It still makes sense and gives a point. Not everything has to be in a strict technical sense, and the person does not have to use pigment names in order to be considered making a valid point on the list. Now I don't even know if it would be really more useful if he had said that in printing his monochrome works, he use certain PKxx, PBxx, PBxz, PYzz, and since he wasn't the manufacturer, he was not sure about the exact proportion, etc. etc. Not every discussion has to be like that. He made his point, and everybody understood it according to the context. > So discussing > colors in terms of hue names just confuses and misleads > people, and I can't see any point in it. And I do not know how many have been confused by my statement, like they didn't know that they could check the pigment names, that they did not know the content of prussian blue but oh thank goodness, this super-knowledgable fotodave must be the president or at least the head engineer at Winsor & Newton, and now he was revealing the secret composition in prussian blue, and they follow my statement to the extreme and are now misled and confused.... :-) Now I need to get back to my cleaning so that I can be ready for painting/gum printing. :-) Dave > > The > > point is simply I was concurring with Judy that indigo is > nowadays a > > hue/tone name. As a mix, each manufacturer is free to use different > > pigments in different proportions. One needs to check the content. > > > > As to listing pigment by pigment numbers, that is always true in > > another context. But here we are not talking about USING INDIGO > > PIGMENT. In fact, the context is the opposite. We are talking about > > indigo not being a pigment in manufactured watercolors but > a hue/tone > > name. > > > > > > Dave > > > > > >> -----Original Message----- > >> From: Katharine Thayer [mailto:kthayer@pacifier.com] > >> Sent: Saturday, December 22, 2007 10:23 AM > >> To: alt-photo-process-l@usask.ca > >> Subject: Re: archivalness of gum > >> > >> > >> On Dec 21, 2007, at 9:13 PM, Dave S wrote > >> > >> > >>> > >>> Same with indigo which originally was made from indigo > >>> > >> plant. It has a > >> > >>> beautiful purple tone, but it is also fugitive. Today's > indigo is a > >>> mixture of prussian blue and quinacridone red. Those who > >>> > >> are used to > >> > >>> true indigo sometimes complain that the synthetic indigo is too > >>> colorful (the true indigo is more muted), but this can be > >>> > >> fixed easily > >> > >>> by adding just a touch of black; so today's indigo is also > >>> > >> a hue name. > >> > >> > >> Well, yes and no. :--) > >> > >> The original indigo that was made from indigo plant and > was imported > >> to Britain from India essentially disappeared around the > turn of the > >> 20th century when it was replaced by a synthetic pigment, > PB 66, also > >> called indigo, that was supposed to be more permanent than the > >> original indigo, but proved not to be. But at least it > was easier to > >> obtain. PB 66 was in use until fairly recently in artist's paints. > >> Winsor & Newton was the last to use PB 66 in watercolor paints but > >> discontinued it last year or the year before, so now I no > longer have > >> to caution people to be extra cautious about paints named > "indigo" to > >> make sure they don't contain PB66, an essentially fugitive pigment. > >> > >> Now all paints named "indigo" are convenience mixtures, as > you say, > >> but it's not true that they all contain the pigments you > name above; > >> in fact in a quick look through my sources I can't find > any made of > >> prussian blue and quinacridone red. Do you know of such a paint? > >> Most "indigoes" are lamp black or carbon black mixed with > a blue; the > >> blues vary all over the place from pthalo to indanthrone (PB60) > >> to prussian. For a while a few brands were adding alizarin > >> crimson, > >> but none of them do now because of its impermanent nature. > >> Winsor & Newton adds beta quinacridone to pthalo and lamp black to > >> comprise their "indigo" but beta quinacridone isn't > quinacridone red > >> (PB 209), or even quinacridone rose (gamma quinacridone); > it's a deep > >> bluish purple quinacridone. > >> > >> This discussion just underscores how important it is to identify > >> pigments by their number; it's the only unambiguous way of > referring > >> to pigments. > >> Katharine > >> > >> > >> > >> > >> > >> > >> > >> > >> > > > > > > > > >
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