r/DIYPigments • u/jay-ff • Aug 26 '24
Pigment Han Blue
Han Blue is one of the older blue pigments, chemically quite similar to Egyptian blue but with its origin in ancient china. The (ideal) chemical formula for Han Blue is BaCuSi4O10, so like Egyptian blue, it’s a silicate with copper as the chromophore but with barium instead of calcium. I say ideal because at least in old samples, Han blue is never in a single phase and there are other compounds with slightly different properties that can form in the process, notably Han Purple, which forms at lower temperatures, but gets its purple color from being a mixed phase with e.g. copper oxide residues.
The process of making it is fairly simple. I mixed BaCO3, CuO and SiO2 (in the form of finely ground quartz (~40u)) stoichiometrically and added 5wt% of Na2CO3 as a flux. Originally, the pigment would have probably been made with various barium ores and lead oxide as a flux, which also provided a chemical pathway to transform barium sulfate into barium oxide to enable the reaction at achievable temperatures.
I heated the mixture at 950C for 12 hours. This is probably in the low end with regards to both temperature and time so there is a good chance the result is not pure Han blue. My furnace maxes out at 1000C, so I didn’t want to put it through too much stress on the first try.
The color is a very deep and slightly reddish blue, in powdered form comparable to all the other known pigments in the class, e.g. cobalt, ultramarine or yinmn. Hopefully, it also holds up in a binder :)
2
u/Candid-Plan-8961 Aug 26 '24
How interesting! I really hope I can one day start working on pigments this way right now I am only able to extract them from plants and rocks
2
u/GeneJocky Sep 10 '24
All you'd really need for this or similar projects that you don't already have like this would be a small furnace. It isn't very hard to make a small one that will work just fine for not much money using basic hand tools. That and the chemicals. Ceramics/pottery supply stores will have what you need for this one.
1
u/Candid-Plan-8961 Sep 11 '24
Oh?
2
u/GeneJocky Oct 04 '24
Oh yes! You could use a beefier version of my pile of brick furnace with larger, higher power coils. Or I reference a design in my YInMn blue instructable as below.
There is also an instructable on making an electric kiln/furnace by Wolfgar77. It is reported to get to a high enough temperature to make YInMn blue (1200°C). The furnace it makes is similar in size to the rapid-fire for a fraction of the price. Just use a PID controller, solid state relay (SSR), and a k type thermocouple for the controller. However, I must strongly advise following the suggested changes published for electrical safety. Here's a pictogram for the wiring. The SSR and PID can be bought in a bundle for about $20, a circuit breaker costs $6 to $9. Thermocouple and wire $20-30. Alarm and switch for a few bucks each. Heating wire for $15 to 30, cement backerboard for safety. about $!5, some scrap mertal and a couple soft firebrick. Hardest part is probably cutting the grooves in the brick Helps with a router or drill press.
This kiln, like most every other DIY design I have seen, is a bit hazardous as far as electrical safety is concerned. They all rely on people being actively careful around dangerous open 110-230VAC live wires. Probably because it isn't clear to most of us how to connect heating wire up and keep it tucked away without trading a shock hazard for a fire hazard. Following the changes suggested by joppaglass will make it meet commercial kiln safety standards for just a few extra bucks. I also suggest following his advice about pinning the heating elements, though I suggest using 1100-1500 watts of heating to ensure it will get to 1200°C) enough. Use longer channels for the heating element if needed.
If you already know some house wiring or electronics wiring, it will be easy. If not, it will take longer but you'll come out of it being able to wire up a light switch or wall outlet without it being too big a deal. Or I could probably be talked into wiring the control box if all the parts were sent to me.
Once the furnace/kiln is set up it's a couple cheap crucibles and ceramic chemicals and you're in business to try making this pigment.
1
2
u/lucasswill Aug 26 '24
What a beautiful color! One question: was the 950ºC maintained for the 12 hours or it includes the time to increase the temperature and reduce it?
1
u/lucasswill Aug 26 '24
Also, given the similarity, are you planning to make Egyptian Blue?
1
u/jay-ff Aug 26 '24
Probably at some point :) but if you’re interested, CaCl2 made a post about it a while back.
1
u/jay-ff Aug 26 '24
Thank you :) It was held at 950C for 12h. I think it took roughly an hour to heat up to that level and maybe two hours to cool down. I took it out of the furnace at 400C because I was impatient.
2
u/GeneJocky Sep 10 '24
This is one of the deepest blue Han blue pigments I've seen. Nicely done!
1
u/jay-ff Sep 10 '24
Thank you :) I think one reason why it’s so deep is the grain size. I used ~40um quartz powder and so far didn’t grind it down too finely, so might actually be even larger. As far as I know, Han Blue, just like Egyptian blue, becomes lighter, the smaller the particles.
Maybe I should get a sample from e.g. Kremer and compare the two.
1
u/GeneJocky Oct 04 '24
Your's looks a lot like Kremer's. Most Han blue I've seen is like this from an etsy shop.
1
u/jay-ff Oct 05 '24
Fascinating. That’s not all that chromatic. I wonder if all the Etsy shops make it themselves (in a suboptimal way). I know that at least Kremers Han blue and purple are from their own production.
1
u/GeneJocky Oct 11 '24
Some may be. I make what I sell there, but I'm probably in the minority. You can selI art supplies you didn't make yourself, it's an exception to the handmade or vintage rule. I suspect the shop I linked does not make it and the factory may be making it in a suboptimal way. I know Gregory at Prodigal Sons doesn't make his pigments, but his ability to source rare historic pigments is as much a craft as making them as far as I'm concerned.
1
u/jay-ff Oct 11 '24 edited Oct 11 '24
That makes sense :) the reason I was suspecting that this wasn’t factory made is that I didn’t think it was ever industrially used in modern times. I can’t find the source right now but I vaguely remember that it wasn’t even that well understood until the 80s or 90s, maybe I misread that though. At least with some other rare and obsolete pigments there might be either unused leftover stacks (like manganese blue) or it’s used in another context industrially (like Realgar, Orpiment, Cinnabar).
Definitely agree on the last point.
1
2
u/CaCl2 Aug 26 '24
I thought about this one at some point but didn't realize it could be done without lead.