Indigosols and heat

jsmoove · Jun 26, 2021

I'm wondering if someone can tell me a bit about light sensitive/light oxidized vat dyes and whether they withstand high heat.
High heat as in a kiln or oven, I'm curious to know if a light sensitive vat dye can be used in a photoceramic method, within a glaze for instance (after exposure, and fixing(?)). What would occur exactly?
Do they release toxic stuff like cyanotype under high heat?
I found this great source: http://www.pburch.net/dyeing/vatdyes.shtml
Where the product inkodye is mentioned (now discontinued). I couldn't find the msds. Nothing mentioned about heat.

gone · Jun 26, 2021

I occasionally make pottery, and seriously doubt anything like you describe would survive kiln temperatures. Even a bisque fire is usually cone 4-6, or around 2,157 to 2,232 degrees F.

koraks · Jun 26, 2021

Dyes, being organic molecules, aren't likely to survive anything above a couple hundred degrees Celsius.

jsmoove · Jun 26, 2021

Thanks, yeah I think someone already mentioned this in another thread to me, just forgot. Makes sense.
By couple hundred, is it something like 300-400?

koraks · Jun 26, 2021

I'd sooner think 100-200 tops.

jsmoove · Jun 26, 2021

So are most indigo glazes inorganic indigos? I don't know much about pottery in general

fgorga · Jun 26, 2021

jsmoove said:
So are most indigo glazes inorganic indigos? I don't know much about pottery in general

Indigo refers both to a specific organic dye and, more generally, to a shade of blue.

As others have said, glazes for pottery that must withstand typical kiln temperatures cannot be made with organic compounds as these invariably oxidize (burn up) at much lower temperatures.

I am a chemist, but have no special knowledge about ceramics or glazes. I took a quick look (via Google) at recipies for indigo glazes and most seem to use inorganic nickle compounds as the main colorant.

Nicholas Lindan · Jun 26, 2021

Glaze colors are inorganic metal based pigments - https://en.wikipedia.org/wiki/List_of_inorganic_pigments

jsmoove · Jun 26, 2021

Ah.....are there inorganic pigments that have a high light sensitivity?
That can withstand kiln temps?

koraks · Jun 27, 2021

Not that I know of. In general, light sensitivity and high temperature resistance don't go well together, because the first requires an unstable molecule, while the second implies a very stable one. I think you need to consider indirect routes where the color itself (pigment or glaze) is not the actual light sensitive component.
Btw I suspect indigo glaze is based on copper.

jsmoove · Jun 27, 2021

I will take your advice on that. I didn't think there was a route with the vat dyes, but I just had to check to make sure.
I'm mostly interested in methods of fusing a photographic image onto glass to make it indestructible.
There are already a few threads in the past on here about cyanotype and photoceramics, and I like the idea of cyanotype..but I don't know about fumes, whether I'd need to kiln fire at a lower temperature so that the glass doesn't melt...whether the resolution would remain, etc. Though itd be in someone else's kiln, I don't own one.

koraks · Jun 27, 2021

I've thought if this as well for a bit, but never pursued it, partly because I have no experience at all with ceramics and kilns. My stepmother has done a lot of ceramics and my parents actually have a pottery kiln, but I just never tried my hand at it.
I think on my searches I did come across those little portraits they made for cemeteries, you know, the little photos of the deceased as they are sometimes put onto the grave markers. These days they are mostly digital prints AFAIK, but if memory serves, they used to use a variant of carbon printing to make those portraits last. I think they actually fired those as well to fuse the portrait onto the substrate. It's something you might want to look into.

jsmoove · Jun 27, 2021

Yes, enamel photography, I think these days they use digital ceramic inks or ceramic decals.
The carbon processes seem a bit tricky. https://enamellers.net/enamel-photography/
I wonder if it's just easier to use liquid light. I was hoping to find some examples of either silver or cyanotype fired onto glass,
https://www.glithero.com/silverware-vases But this isn't fired im pretty sure.
Maybe coating a glaze or vitreous enamel over top the photo on glass would be an idea....I'm not sure about the COE.

glbeas · Jun 27, 2021

I have experimented with van dyke on a ceramic tile and I was able to get an image on to the tile. That being iron salts making the image theres a good chance it would survive being fired with a clear glaze. You can also tone the image with gold or other salts to enhance the durability. Theres toners to make other colors but its a wild guess as to what color it will be after firing.

Nicholas Lindan · Jun 27, 2021

There is a process used for making images for headstones. https://www.amazon.com/All-Italian-Imports-ceramic-memorial/dp/B01KKMS68U (seems Amazon files funerary items under "Home & Kitchen Supplies).

I have mugs from the Cleveland Museum of Art with very high quality reproductions of various Van Gogh, Cezzane and Monet paintings. I imagine the pigments were put down with an ink-jet process, a glaze applied over the image and the mug fired.

You could also try a silk-screen process. A Gestetner photo stencil is a possibility, well not really unless you have a time machine. The process is still used to convert photographs to printing screens for producing t-shirts.

koraks · Jun 27, 2021

glbeas said:
That being iron salts

In a finished a d properly processed Van Dyke, no iron salts remain, so it's all silver unless toned as you mention.

Nicholas Lindan said:
I imagine the pigments were put down with an ink-jet process, a glaze applied over the image and the mug fired.

I highly doubt the mugs are fired after printing. I suspect they coat the pigment prints with something like a polyurethane varnish.

fgorga · Jun 27, 2021

koraks said:
In a finished a d properly processed Van Dyke, no iron salts remain, so it's all silver unless toned as you mention.

I highly doubt the mugs are fired after printing. I suspect they coat the pigment prints with something like a polyurethane varnish.

I am not sure that you would get much of an image with any metal (silver, gold, etc.)... silver melts at 962 deg. C and gold melts at 1064 deg. C. The temperature quoted above for a kiln (i.e. ~2200 deg. F or 1200 deg. C) is above the melting temps. Thus one might expect a very fuzzy image if you get one at all. Furthermore, there is the issue of oxidation. Neither silver or gold is inert. I would expect significant oxidation of both metals at kiln temperatures if oxygen is present. You would stand a better chance with a platinum image... melting point 1768 deg. C and much less reactive. Of course, then there is the matter of the expense! ;-)

As for mugs with colored printing, I believe that these are made by a dye sublimation process... the image is printed with special inks onto a transfer paper. The paper and the mug are then placed in a press under heat and pressure to transfer the image from the paper to the mug (or other surface). The process is very similar to the Chromaluxe process for making prints on aluminum. It requires fairly modest heat.

jsmoove · Jun 27, 2021

@fgorga
What about mid-range temperatures? In the vitreous enamel range? 750 - 850 celcius. Would the image fuse to glass at this temperature? If silver.
Or cyanotype? Which would be the least expensive.
I guess it would depend on what the melting point of the glass is.

fgorga · Jun 27, 2021

jsmoove said:
@fgorga What about mid-range temperatures? In the vitreous enamel range? 750 - 850 celcius. Would the image fuse to glass at this temperature? If silver.
Or cyanotype? Which would be the least expensive.
I guess it would depend on what the melting point of the glass is.

I have no idea regarding the fuse-ability of an image, you'll need to experiment. At least at those temperatures the metal will remain solid. I have no idea about the rate of oxidation at those temperatures, but if you are going to be fusing under a clear glass, it might, and that is a big MIGHT, work.

As for cyanotype, I doubt that it would work in any of these processes. Prussian blue, the pigment formed by the cyanotype process, is not all that stable.

According to https://pubchem.ncbi.nlm.nih.gov/compound/Prussian-blue

"Iron blue pigments are thermally stable for short periods at temperatures up to 180 °C...The powdered material presents an explosion hazard, the ignition point is 600-625 °C...The pigments are combustible in powder form, ignition in air being possible above 140 °C"

jsmoove · Jun 27, 2021

Yikes, explosions!
What about pouring a vitreous enamel overtop an already processed silver or cyanotype image already on glass?
To make the image fossilized forever.
I imagine still there would be combustion issues? And thermal expansion issues? With enamel shrinking on glass.
Actual glass enamel, not the plastic stuff.

Actually, what about the original question for vat dyes? Enamel over vat dyes on glass?

Nicholas Lindan · Jun 27, 2021

koraks said:
I highly doubt the mugs are fired after printing. I suspect they coat the pigment prints with something like a polyurethane varnish.

No, they are fired, just like any other coffee mug or ceramic food dish. It's not any sort of earth shaking technology - rather than painting on the ceramic design with a paintbrush it's ink-jetted.

Do you have any ceramics with a faux-glaze urethane finish?

fgorga · Jun 27, 2021

jsmoove said:
Yikes, explosions!
What about pouring a vitreous enamel overtop an already processed silver or cyanotype image already on glass?
To make the image fossilized forever.
I imagine still there would be combustion issues? And thermal expansion issues? With enamel shrinking on glass.
Actual glass enamel, not the plastic stuff.

Actually, what about the original question for vat dyes? Enamel over vat dyes on glass?

I'd not worry about explosions with an image. The text I cited is referring to powdered pigment, not small amounts absorbed to a surface.

As for your idea about sealing an image with clear enamel... again, I doubt that it would work because of the binder needed to get the image to adhere to the glass in the first place.

In all that I have read (again,I have no first hand experience) one needs an organic binder (gelatin, albumen, polyvinyl alcohol, etc.) to get the photo chemistry to stick to the glass. I doubt that any 9f these substances would stand up to the heat you are suggesting.

Experiments are the way to find out.

fgorga · Jun 27, 2021

Nicholas Lindan said:
No, they are fired, just like any other coffee mug or ceramic food dish. It's not any sort of earth shaking technology - rather than painting on the ceramic design with a paintbrush it's ink-jetted.

Do you have any ceramics with a faux-glaze urethane finish?

Partly correct, items such as mugs are inkjet printed.

However, they are not fired after printing.

Items such as mugs using a dye sublimation transfer process, see https://www.instructables.com/Photo-Mug-Dye-Sublimation-Production-Process/ for a simple overview and lots more info via Google.

The products stand up quite well to everyday use, including the dishwasher.

Nicholas Lindan · Jun 28, 2021

Well, I'll be damned. And wrong. Well, half wrong and half damned.

I took a steel knife to one style of mug and a bit of the image on the mug sliced right off. The damn 'glaze' is bloody plastic! My certainties in life are shattered. And now I may need to get a new mug if the water starts getting under the cut in the plastic.

The other set of mugs don't have the high gloss of the first set with the plastic glaze. The finish is slightly pock-marked. These mugs have a standard ceramic glaze on them (or the plastic is harder than a Wusthof steak knife).

As in most things, it seems there is more than one way to paint a mug.

koraks · Jun 28, 2021

Nicholas Lindan said:
My certainties in life are shattered.

Don't worry - we've got cookies on our side

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