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indraneel
10-28-2014, 04:35 PM
Hi, any chemists here? Is it possible to make viridian (hydrated chromium oxide; PG18)? I have tons of (anhydrous) chromium oxide (PG17). I searched and searched and all I could come up with is to either add an acid and then a base, or to start with some salt of borax and then refine. I'm looking for a recipe which will not inadvertently create the toxic Cr(+6), and also can be done at home. Just a little bit, maybe 100 grams will do for now. Nobody seems to sell viridian pigment powder where I live, as it's not used for ceramics, and PG7 takes care of the rest.

Thanks a lot in advance for any help!

Gigalot
10-28-2014, 05:08 PM
You need potassium bichromate, borax and powdered sulfur. Those ingredients must be powdered, mixed and heated several hours in crucible at a high temperature. Then it must be milled, and pigment must be extracted with hot water and then washed.

You can dissolve PG17 in acids only in mythology. I did many experiments to dissolve PG17 in nitric acid, in HCl, in Sulphuric acids in my stormy, chemistry childhood.
Forget about this way. It might be easier to dissolve toilet sink in citric acid :D .
PG17 is the most permanent pigment in the world.

The only way to attack PG17 is to dissolve it by heating with melted NaOH at a high temperature in oxygen conditions. You can make sodium chromate from it.

Patrick1
10-28-2014, 05:34 PM
The only way to attack PG17 is to dissolve it by heating with melted NaOH at a high temperature in oxygen conditions.
This is something every good art teacher demonstrates to their students when teaching color theory...a blast furnace is standard equipment in any studio :lol:

Gigalot
10-28-2014, 05:45 PM
This is something every good art teacher demonstrates to their students when teaching color theory...a blast furnace is standard equipment in any studio :lol:

I was 12 or 13 years old, tried to dissolve Chromium oxide in acids at home but nope! I took Cobalt-Chromium blue-green oxide PG26 instead, but nothing happened. Those pigments are rock solid substances! :lol: I remember, I was very, very angry!

WFMartin
10-29-2014, 12:16 AM
Holy Cow! There is no specific color in this world (much less a "green") for which I would exert this degree of effort to obtain! Not when I can purchase something close to it that is available in a tube.:D Just call me "lazy", I suppose, but......really!?

karenlee
10-29-2014, 10:11 AM
Another holy cow (OP is in India).
Gigalot, that was quite a childhood experiment!!!! :eek:

Gigalot
10-29-2014, 02:46 PM
Holy Cow! There is no specific color in this world (much less a "green") for which I would exert this degree of effort to obtain! Not when I can purchase something close to it that is available in a tube.:D Just call me "lazy", I suppose, but......really!?

I had never tried to create this pigment at home because I have it in a tube. It might be better to purchase it online if any. :) And pigment heating at 600 Celsius degree during six hours can be problematic at home conditions!


Gigalot, that was quite a childhood experiment!!!! :eek:
Almost non-toxic experiment :angel: Nothing interesting, I was very disappointed! But Cobalt blue deep PB74 dissolved easily in HCl. It makes a rose-colored gel.

indraneel
11-03-2014, 02:06 AM
Well holy cow (yeah, it's holy, it does give ample supplies of raw umber, and the mythical yellow, or not...)! My dad had a blast furnace at work, but since he's retired... maybe I'm out of luck :( Seems like I might have better luck scraping off old green doors.... time to make the rounds of historic buildings...

What's interesting is how so many of you have already over exerted yourselves in search of pigments... seems I touched many raw nerves :D

Problem with viridian tubes are they contain fillers, unless I go for the really pricey ones... and I'm not too sure how much I'll be using it. Just thought there may be a quick way to outsmart the tube packers... :(

Anyone knows which industry viridian is used in (other than artist pigments)?

Gigalot
11-03-2014, 02:41 AM
Anyone knows which industry viridian is used in (other than artist pigments)?

No industrial usage, it was replaced everywhere to PG7. PG7 has better color, better price, better stability and high tinting strength. In ceramic, glass and bottle manufacturing, camouflage, abrasive industry, anhydrous Chromium Oxide PG17 is widely in use.

But Potassium Bichromate and Boric acid are widely available :D

indraneel
11-03-2014, 11:11 AM
But Potassium Bichromate and Boric acid are widely available :D

you also said powdered sulfur :(

Anyway, I think this will have to wait. I just discovered that my handmade watercolor paper is too heavily sized with gelatin and repels water; no wonder my washes always ended up too thin (and PG7 is non staining). I'll probably have to add some KOH to the gum arabic to bring it to neutral pH. So hopefully the colors will finally flow from the brush. It did work after adding the liquid dishwashing detergent... I got a sample of arches and the colors are so bright because the pigment ends up on the paper instead of remaining in the brush...

I wonder if PG7 can be made granulating...

Gigalot
11-03-2014, 11:19 AM
you also said powdered sulfur :(

Anyway, I think this will have to wait. I just discovered that my handmade watercolor paper is too heavily sized with gelatin and repels water; no wonder my washes always ended up too thin (and PG7 is non staining). I'll probably have to add some KOH to the gum arabic to bring it to neutral pH. So hopefully the colors will finally flow from the brush. It did work after adding the liquid dishwashing detergent... I got a sample of arches and the colors are so bright because the pigment ends up on the paper instead of remaining in the brush...

I wonder if PG7 can be made granulating...

Sulfur is a mistake, it makes PG17 with potassium Chromate heating.
It might be better to use NH4OH ammonia solution instead of KOH.
BTW, Viridian is a weak pigment, in watercolor it might be too weak to be good! Ask watercolorists about it's usability...

NOTE: DANIEL SMITH almost always use colorants to improve their pigments. Their "Viridian" can be somewhat genuine viridian base with Phthalo Green precipitated on it. And 90% of it's color strength can be a Phthalo PG7 color.
Check all other viridian watercolor manufacturers and if DANIEL SMITH is only one who can make viridian - then you will have a good Phthalo filled with viridian. :D If watercolorists gives you DANIEL SMITH viridian advice - just remember me :lol:

indraneel
11-03-2014, 02:35 PM
hmm... why ammonia solution instead of KOH?

Don't worry about Daniel smith, it's not available here. Only options are the atrociously priced WN (never discounted) or the "filler filled" Daler Rowney. Sometimes a few dubious ones like Schmincke or Sennelier pop up.

Mythrill
11-03-2014, 02:40 PM
hmm... why ammonia solution instead of KOH?

Don't worry about Daniel smith, it's not available here. Only options are the atrociously priced WN (never discounted) or the "filler filled" Daler Rowney. Sometimes a few dubious ones like Schmincke or Sennelier pop up.
Indra, of all the paints, watercolors are the easiest to make. Since you don't have many options, have you considered buying your own gum arabic and making them?

indraneel
11-03-2014, 07:01 PM
Indra, of all the paints, watercolors are the easiest to make. Since you don't have many options, have you considered buying your own gum arabic and making them?

:angel: uh oh, I make all my paints (thus trying to find viridian powder), though not from rocks like you... :evil: The first post from last year is here http://www.wetcanvas.com/forums/showthread.php?t=1328360
I buy my gum arabic from a spice trader, it comes from Arabia :evil: (well not really, but close enough :D ) Also, somehow have a couple of bottles of acrylic binder, even though I don't paint acrylics :eek: Ditto for linseed oil, microcrystalline wax and gum tragacanth. The last one is being used, slowly... :)

Mythrill
11-03-2014, 07:25 PM
:angel: uh oh, I make all my paints (thus trying to find viridian powder), though not from rocks like you... :evil: The first post from last year is here http://www.wetcanvas.com/forums/showthread.php?t=1328360
I buy my gum arabic from a spice trader, it comes from Arabia :evil: (well not really, but close enough :D ) Also, somehow have a couple of bottles of acrylic binder, even though I don't paint acrylics :eek: Ditto for linseed oil, microcrystalline wax and gum tragacanth. The last one is being used, slowly... :)

Oh, I saw that thread! Your paints and pigments are beautiful!

There's nothing like making your own paints, right? It's your consistency, your pigment load and your handling!

Speaking of it, do you sell pigments? If so, what do you sell? I can't buy anything now, but I'd like to keep you in mind if I need some!

indraneel
11-04-2014, 03:44 AM
Thanks Mythrill ! No, I don't sell anything, yet. Selling in India is a nightmare because of corrupt bureaucratic hurdles... one can easily end up having to bribe someone in order to pay taxes. I buy most of my non ceramic pigments from the recently started (at my instigation :) ) http://www.pigmentkart.com/ but I'm not sure if they've started shipping internationally. The owner said he was planning to, a few months back (to recoup costs, because retail sales was a risky headache).

I don't think there's a retail outlet for the ceramic industry pigments (the heavy metals), and being toxic I'll probably not be taking the risk of shipping hazardous materials. The owner does not seem to be too interested in starting a retail outlet either.

Gigalot
11-04-2014, 06:28 AM
Thanks Mythrill ! No, I don't sell anything, yet. Selling in India is a nightmare because of corrupt bureaucratic hurdles... one can easily end up having to bribe someone in order to pay taxes. I buy most of my non ceramic pigments from the recently started (at my instigation :) ) http://www.pigmentkart.com/ but I'm not sure if they've started shipping internationally. The owner said he was planning to, a few months back (to recoup costs, because retail sales was a risky headache).

I don't think there's a retail outlet for the ceramic industry pigments (the heavy metals), and being toxic I'll probably not be taking the risk of shipping hazardous materials. The owner does not seem to be too interested in starting a retail outlet either.

There are so many Lead pigments on pigmentkart! Great!!! So many fiery lead yellows, red lead and lead orange pigments are there. Impressionists Dream! Fantastic place! :)

indraneel
11-04-2014, 07:12 AM
There are so many Lead pigments on pigmentkart! Great!!! So many fiery lead yellows, red lead and lead orange pigments are there. Impressionists Dream! Fantastic place! :)

Yes, I have to be careful not to click on them :angel: . And no, you're not getting them from me either :lol:

Gigalot
11-04-2014, 04:30 PM
Yes, I have to be careful not to click on them :angel: . And no, you're not getting them from me either :lol:
:crying: Lead chromate-molybdate pigments are very beautiful! Lead is prohibited in Evil Union of Euroaucracy. :D

Barbareola
11-05-2014, 11:56 AM
Don't worry about Daniel smith, it's not available here. Only options are the atrociously priced WN (never discounted) or the "filler filled" Daler Rowney. Sometimes a few dubious ones like Schmincke or Sennelier pop up.

Out of curiousity: why do you consider Schmincke "dubious"? I have heard a lot of opinions about Schmincke, but never that.

indraneel
11-06-2014, 07:17 AM
Out of curiousity: why do you consider Schmincke "dubious"? I have heard a lot of opinions about Schmincke, but never that.

Mostly because I have to hunt for single pigment colors of good lightfastness, but also because they are sold here as very pricey trial packs. The handprint review is not favorable either. ... same problem with Sennelier...