> >A note [in the Kremer booklet] 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.
Peter replied:
> This would also explain why they fade more easily
>Why? As I recall, most of the cadmium colours are in the 3-star or "good"
range. Why would being "usually opaque" make them fade more easily? <
Sorry what I should have said was. This would explain why the transparent
yellows fade so easily as they are mostly organic in origin, it was in my
mind but did not come out right a common occurrence :-)
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,<
I was not referring to your footnote, it was the information in
The Paper Conservator," that caught my attention. I did
not delete your foot note out of respect for you.
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],
Don't get racialist Judy the problem is that I have a short attention
span and you write such a lot
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.....
Yes for me you did not explain clearly enough, never mind that is my
problem not yours
> We Brits may be aggravating....
>Yes.
Sorry Marm :-)
pete