Friday, January 29, 2010

Transmittance

Steady progress. Colours used; French Ultramarine, W/N Burnt Sienna, Yellow Ochre, Titanium White.

Blockx Transparent Mars Brown is the same colour as Winsor and Newton Transparent Red Oxide. I'm wondering if Blockx Transparent Mars Red is the same colour as Winsor and Newton Burnt Sienna (both PR101; not natural earth).

4 comments :

-Don said...

My answer would be yes based on my understanding of the PR number. Our friend, Kathy, would probably know for sure with her chemistry background... -Don

Kathy said...

Mark, I can't compare the two manufacturer's products without going to their websites to see if the pigments are the same, but I can tell you a little bit about the standard chemical formulas for some of these colors. Mars brown is an inorganic synthetic iron oxide (two irons bonded to three oxygens) and has the same general properites as the pure red oxides. Mars red is also an inorganic synthetic iron oxide with the same chemical formula as Mars Brown. However, the manufacturer's processing makes it more red. Burnt sienna is the same chemical species as well, but is produced from ores and has been calcined in a furnace. That, alone, would lead me to believe that the Blockx Transparent Mars Red could be different from the Winsor and Newton Burnt Sienna. But, I really don't know without reading the manufacturer's labels.

Mark Sheeky said...

I forgot to say that the Mars Brown and Transparent Red Oxide are also PR101. Sometimes the same pigment codes can mean different colours; there are no standard for Cadmiums for example so a cadmium yellow pale might be an actual different degree of orange with a different manufacturer, although some like ultramarine tend to be the same everywhere. Winsor and Newton use a natural raw sienna, but their burnt sienna is a synthetic iron oxide which is darker and cleaner. The Blockx tube isn't too expensive so I suppose there's only one way to find out for sure...

-Don said...

What a great chemistry lesson! Thanks... -Don