Peter replied:
> This would also explain why they fade more easily
Why? As I recall, most of the cadmium colors are in the 3-star or "good"
range. Why would being "usually opaque" make them fade more easily?
I had also copied extracted from an article in "The Paper Conservator,"
> >"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.'"
To which I added a footnote saying that:
> >[This is what I was trying to say about fine grinding with a ball mill.]
Now Peter says,
> This is a very important piece of new information
No it isn't. I've said *exactly* that on list in one form or another 3 or
4 times since February, some of it perhaps in direct mail to a single
person, but still several times to list at large. Therefore I surmise,
a. you don't pay attention, or,
b. you don't pay attention when I say it, or,
c. you don't pay attention until the Brits say it, or,
d. --------------- [you fill in the blank]
I quoted further:
> > "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...."
Which you declared,
> Again great stuff I have never fully understood what a surfactant was, this
> clear explanation has remedied that ....
Perhaps I failed to explain clearly enough, Peter, but I covered this
material several times. First after College Art in February when I quoted
Mark Golden's explanation about dispersal agent (surfactant) and again
quite recently in discussions of pigments and grinding.....
> We Brits may be aggravating....
Yes.
Judy