Reactive and Non-Reactive Pigments

[Saturn]

I sent the same message two times while trying to edit my post and now I am deleting the second time. Apologizes!

[llawrence]

Thank you again Saturn.

Originally posted by Saturn:
The natural and the artificial cooper blue pigments are not exactly the same. For example many natural blue Azurites are Hydroxo copper carbonates, while the blue bices are Basic Copper Calcium Carbonates. The calcium comes from the action of lime on the unfinished green product.

I've been confused then: I didn't realize that the bice pigments were the copper-lime compounds. I was thinking of the simpler blue and green artificial hydrated copper carbonate pigments.

I notice on the blue verditer product page that that pigment is recommended to be ground with lead white when using it in oil. What is the crucial difference then between bice and verditer, I wonder? Is the verditer the one that does not contain lime?

[Saturn]

[/qb][/QUOTE]I've been confused then: I didn't realize that the bice pigments were the copper-lime compounds. I was thinking of the simpler blue and green artificial hydrated copper carbonate pigments."

I am not commenting any of the NP products or pigments. My comments were general and not in regard to any specific brand of pigment.
In fact I am not familiar with the nature of the
copper pigments that NP sells at this site.
Perhaps George will give you the information that you need about the NP pigments.

"I notice on the blue verditer product page that that pigment is recommended to be ground with lead white when using it in oil. What is the crucial difference then between bice and verditer, I wonder? Is the verditer the one that does not contain lime? "

Yes, the Blue Verditers that I am familiar of were not described as containing lime.

[Saturn]

I found that there is a bit of confusion between the terms verditer and bice and that this confusion is not from today, but existed yet in the Baroque and later times.
I have made my own bice in my studio using a proces which produces green variety of pigment , which then when mixed with certain amout of lime and exposed to dry in the open air turns blue.
This I suppose is what should be understood by the term bice.
I have also made in my studio artificial malachite which is very fine, but lacks in covering power. I have made verdigris both in the traditional and the modern artificial way and I am not very impressed by its quallities. However all the artificial and natural varieties of copper blue pigments turn green when mixed in oil.
When the blue artificial pigments are badly made they can turn green after a week even in a glue or tempera binder.

[ 23. June 2010, 19:14: Message edited by: Saturn ]

[llawrence]

Very cool Saturn. I've made the artificial malachite from copper sulfate, which I really like in oils or gouache. I haven't had the same problems with covering power, the one I made seems fairly opaque to me.

The lime blue I made was different: I dissolved copper sulfate in an excess of ammonia, then precipitated with lime. It's a nice color, but I haven't tried it in an oil paint yet. In watercolor it turns green pretty quickly, but it seems fairly stable in egg tempera - at least, it's lasted about six months or so.

I haven't made or used verdigris yet. What didn't you like about it?

[Saturn]

"Very cool Saturn. I've made the artificial malachite from copper sulfate, which I really like in oils or gouache. I haven't had the same problems with covering power, the one I made seems fairly opaque to me."

I made mine with sulphate too, by means of participation. I did not like any of the artificial cooper geens and blues by the way.
The natural varieties are best for my taste.


"The lime blue I made was different: I dissolved copper sulfate in an excess of ammonia, then precipitated with lime. It's a nice color, but I haven't tried it in an oil paint yet. In watercolor it turns green pretty quickly, but it seems fairly stable in egg tempera - at least, it's lasted about six months or so."


Most of the blue artificial pigments call for some sort of alkaline substance like lime or amonia. The cooper pigments turn blue in contact with alkalies like aminia, but usually when the ammonia evaporates, they return to green again.
This is why they use lime which does not evaporate.

"I haven't made or used verdigris yet. What didn't you like about it? "

The Verdigris I made for a first time 17 years ago when I read the directions for it's production written by the writers of some manuscripts which date from XI to XV centuries.
I wanted to experiment and get a better idea of the nature of this material and did it exactly in the said way. Th eresulting produc was too bluish green. This is what I did not like. It's colour.
I tried to use silver too, which according to the olden manuscripts was also employed( suppose from the copper content it had) and the resulted verdigris had the same bluish colour. Later I used a more modern process for making it which had better results, but I have never been real fan of Verdigris in painting. Mostly because there are excellent replacements to use nowadays which are not reactive and toxic.
I have made all the above experiments from motives of curiosity , for there is almost no known material for painting that can be produced in studio , which I have not made.

Much higher success I have had with producing transparent iron oxide pigments, which I loved , both because of their deep and pure colours and intresity and their huge trasnparency. The so called translucent mars pigments.
They however require great deal of washing afterwards, which consumes much time and makes the said process unpractical. But as I told you above I have always been lead by motives of curiosity. Thanks to this fact , nowadays I am very bad client for ready-made paints in tubes, mediums and one big number of paint materials. I just make them in my studio in the way that I wish and in the amounts that I need.

[George O'Hanlon]

Originally posted by llawrence:
I notice on the blue verditer product page that that pigment is recommended to be ground with lead white when using it in oil. What is the crucial difference then between bice and verditer, I wonder? Is the verditer the one that does not contain lime?

There is a difference between blue bice and blue verditer, although chemically they are similar. The both are processed with calcium compounds, but using different methods. The result is that the blue verditer is more stable in oil than blue bice. Blue verditer does darken, however, to some degree and this is why we recommend mixing it with lead white, as the degree of darkening is not noticeable in this mixture.

Overall, the issue with blue copper carbonate pigments is that tend to revert to green copper carbonate when used in oil. Some of this is caused by the yellowing of the oil or varnish layer, some caused by a conversion of the ionic form of the copper.

[llawrence]

Thank you for the explanation.

This page shows a cross-section of a fourteenth-century painting layer of mixed verdigris, lead white and lead-tin yellow:

Webexhibits

Some artists appear to have been able to make this work.

[Saturn]

Originally posted by llawrence:
Thank you for the explanation.

This page shows a cross-section of a fourteenth-century painting layer of mixed verdigris, lead white and lead-tin yellow:

Webexhibits

Some artists appear to have been able to make this work.

You will find many sources which give direction to mix verdigris with white, black and other pigments and equal numbers of cautions not to do it. Why instead of wondering don't mix it with white and see yourself?

[llawrence]

I will certainly do that - I just received my first tube of lead white from Rublev, and I'm looking forward to trying it out with verdigris. But as I do I'm also trying to find out as much as I can, to minimize my stupid mistakes.