Here is a copy of my reply from old forum:
___________________________________________________Mr Antonov,
I would like to clear up my point (in case I was not clear enough in my previous posts), and - with all due respect - to react on your notes on paints Rubens used (http://www.1art.com/tips.htm#Flemish).
I am not chemist nor conservator, though I read every article on painting technology and painting chemistry I can find, because archival quality of my painting is of great importance to me.
When I mentioned that, in my opinion, we would be more faithful to the spirit of old masters if we use the best art material available today, I meant that if old masters were alive today, they would do the same thing.
Perhaps Leonardo, who was very fond of experimenting, would try acrylics or alkyds, who knows 
Every painter choose material that best suit his/her needs. My intend was not to patronize fellow artists, but I have read and heard enough on that subject (from serious artists and scholars) to participate on an open forum like this.
Since you asked me to show you available substitutes for old masters' pigments, I can only say that it is not necessary (I have never claimed that all those pigments should be substituted). Painters who lived prior to 18th century have not had a lot of reliable paints available, so their palettes consisted mostly of earths, which was good, because ochres, umbres, siennas, etc are among the most permanent pigments known.
However, some of their paints were less stable - Rose Madder (NR9), for instance.
It is a dye made from the dried roots of the herbaceous perennial rubia tinctorium. The plant was brought to Italy by the returning Crusaders, and became important as an artist's pigment after it was imported to Holland in the 16th century. It contains two organic colorants: the orange purpurin and the deep carmine alizarin. Both pigments are impermanent, but purpurin is especially fugitive.
Rose Madder (Madder Lake) has a beautiful hue, but because of the reasons I have explained, I use Quinacridone Rose or some of the cool red DPP pigments (PR255, PR264).
Besides being a painter, I teach art history, but I can not say for sure anything on Rubens' palette, except what I read in scholars' papers.
I am sure your knowledge of flemish technique is considerable.
However, I doubt that Rubens used Prussian Blue (PB 27).
That, green-blue mineral (ferric ferrocyanide) color was the first modern, artificially manufactured paint. It was made by the colormaker Diesbach of Berlin in about 1704. Diesbach accidentally formed the blue pigment when experimenting with the oxidation of iron. The pigment was available to artists by 1724. Rubens died in 1640.
