>In this promise I was mistaken. As of current writing I have not located
>the booklet, which wasn't in the "pigment" folder, the "company catalogue"
>folder, the "supplies" folder or the "college art" folder. There's no
>mystery about this, as it is well known that beings from another galaxy
>slip in under cover of darkness and, using their telepathic powers to
>foretell what you will need next, bury it under your 1989 income tax
>receipts.
Thats funny I think they often pay me visit too
>"Organic manufactured pigments are synthesised from organic chemicals.
>They are usually bright, light in weight and transparent. We have
>selected the most lightfast pigments from the hundreds available today"
>A note about "inorganic manufactured pigments" says colours containing
>metals are "usually opaque", which I believe would include the cadmium
>yellow I believe it was Bernie mentioned.
.
This would also explain why they fade more easily
>And tho my search for the Gamblin booklet was frustrating, it put in my
>hands another fine item, an article titled "Factors Influencing the
>Wash-Fastness of Watercolours" by Vincent Daniels, from "The Paper
>Conservator 19, 1995, sent to me by a kind friend.
>
>Here's an example:
>
>"Most pigments have a broad range of pigment sizes and synthetic organic
>pigments and carbon black particles are sometimes as small as 0.01u in
>diameter. The ease with which particles stick to fibres increases as the
>size of particle decreases. Jones reports that particles below about
>0.2u are 'virtually impossible to remove from cotton cellulose except by
>drastic mechanical action, and washing is difficult even with particles
>as large as 5u.'"
>[This is what I was trying to say about fine grinding with a ball mill.]
This is a very important piece of new information
> "Almost all watercolour paints contain a surfactant which helps to
>disperse the pigment in the gum and subsequently over the paper. Pigment
>particles naturally tend to aggregate and need mechanical action to break
>them up. A detergent can coat each pigment particle with molecules which
>change its electrical charge. This makes the individual particles
>mutually repulsive, breaking up aggregates and giving them affinity for
>water...."
Again great stuff I have never fully understood what a surfactant was, this
clear explanation has remedied that
>And so forth. I believe this is a British publication.
We Brits may be aggravating but we do have our uses :-)
Thank you Judy for all the information,
pete