Self-study of pigment and do some notes and bookmarks here. Comments, suggestions and corrections are welcomed.
This is also my entry of the Science Picture Challenge 3 :
@mcw/red-science-picture-challenge-3-with-sbd-3-sbd
Basic information
Brand: Holbien Watercolor
Name of color: Cadmium Red Light (W014) & Vermilion (W018)
Pigment (C.I.)[1]: PR108
Original: artificial
Minerals: greenockite & hawleyite
Formula: CdSe
Both of them are come from same materials, varies in hue is the result of changing of formula.
The range of cadmium pigments, yellow, orange, red are basically cadmium yellow (cadmium sulfide) with some selenium added in place of sulfur (cadmium selenide). Therefore cadmium sulfide can be made in various shades ranging from yellow, orange to red. indeed, mineral pigment produced from cadmium sulphide when heated with selenium becomes red.[2]
The recipe of Holbein of making W014 and W018 can not be found, can't get more detail of the ratio and heating time or degree while making both colors.
Another discovery:
I searched the formula of Vermilion[3], also aka Chinese red and found the Holbein Vermilion is not exactly the same thing with the one I usually heard of.
Color: Vermilion
Pigment (C.I.): PR106
Origin: mineral and artificial
Mineral : cinnabar
Formula: HgS
Therefore, although Holbein named its red watercolor tube as Vermilion, it is not the "true vermilion". It can be considered as a color very closed to vermilion (in my opinion). It is also a factor of concern while choosing tube/pans. As a little conclusion, the name may not truly represent the color. The ingredient/pigment tells what it is.
中文的部份我簡單地總結一下，資料部份就不再寫了（懶）。這次是拿手上有的兩支紅色水彩來研究一下。兩支都用同一個PIGMENT PR108，然而硫化鎘加上不同量的硒加熱，可產生不同程度深淺的紅。 又，在荷爾拜因的朱紅色管上，標的是PR108。然而真正的朱紅色C.I.是用PR106，來源跟成份都跟荷爾拜因的不同。 所以小小結論是，選顏料時不是看名字，要看PIGMENT的標示比較可靠。
（非常歡迎指正，因為科學盲的我只是順藤摸瓜地瞎找資料的）
Reference:
Pigment list with brand
Holbein Safety Data Sheet
Cadmium Yellow/Red basic information
Vermilion basic information
PR108 basic information
Further reading:
Cadmium: The rare paint pigment faces a Europe-wide ban and artists are seeing red
Band gaps in natural semiconductors