The geo-chemistry behind Rookwood pottery


#1

[Read the post]


#2

The worst thing is that these days, the subtleties of a lot of art pottery are being counterfeited overseas and sold as the real thing. They’re usually close, but no cigar, and unless the buyer has educated themselves thoroughly, they are sold a sophisticated fake.

I did my undergrad degree in ceramics. Those original glazes…yum!!


#3

Isn’t geochemistry (and chemistry of glasses and ceramics) fun? :smiley:


#4

“One mineral Robinson knows well is feldspar, two of whose alkalis, potash and soda, are common ingredients in clay.”

This is a confusing way of describing something very real and important. The alkali metals that form the basis of potash and soda ash, K and Na, are important constituents of many clay minerals. These 2 common elements are therefore important & common parts of most clay deposits.

Potash and soda ash are mined in locales that aren’t usually ‘clay deposits’ per se, but they are critical components of the glazes used to produce Arts & Crafts pottery.

I’m probably doing a poor job of explaining this myself; it’s well outside my area of expertise. There is a big difference between the provenance of clays used to make fine art pottery, and the glazes that (also) make them distinctive.

Could someone knowledgeable take it from here?


#5

It helps to realize that a glaze is more similar to glass than to ceramics.

Lead is pretty often used in the glazes, too. The ratio of its stable isotopes could be used for geographically locating its source.


#6

Still one of the best classes I ever took. Raw materials in the hands, going all the way from earth to utensil, and the glazes doing crazy chemistry stuff in the glowing heat of the furnace, absolutely loved it. I’ve gone so far as to consider building a wheel and mini-furnace in my backyard to fire clay.

“Oh, I’m absolutely crackers for geology,” Robinson confirms...
Of the many flavors of "delightful", this is a pretty good one.

#7

I remember fighting with my glaze formulas and oxidation vs. reduction times (we had gas fired kilns) trying to get a nice celadon or ox-blood red consistently, or test a special effect. It had the rush of gambling, because even a location change in the kiln would alter how a glaze turned out, and you wouldn’t know for at least 2 days while the kiln reached temperature, then cooled enough to unload. Once, we ran out of tin oxide, and many of us were reduced to scraping the sides and corners of the bin, trying to get a half teaspoon for our glazes.

Lead is a nasty, because you don’t want to use it on eating dishes (too prone to leach into food if mishandled), but we had plenty of other questionable substances we used in glazes. Fortunately, once fired, even the most exotic ones (like cobalt) were pretty much bound securely into the glaze; occasionally you had to be careful about compounding and firing, because particles and vapors could get loose. Most of the stoneware clay bodies we used were comparatively uncomplicated and non-toxic, unless you wanted a porcelain or other unusual mix. Did you know you could make a sunny yellow with uranium?


#8

please , PLEASE do NOt eat the yellow paint !! nor many of the yeLlow glazes !!


#9

Nor the yellow snow.


#10

And a beautiful bright orange.

I have an old (100 years or so, pre-WW2 certainly, pre-WW1 possibly) ceramic vessel with orange structures painted on it. They make my Geiger sing. I should try autoradiography with them.


#11

At one point, my family had an extensive collection of Fiestaware, including the notorious red-orange which was uranium enriched. I would have loved to pass a Geiger counter over some of those old plates.


#12

I found my one by playing with the Geiger next to the wooden cabinet and noticing that at one point it ticks barely noticeably faster. When I scanned the inside of the cabinet, one item made the counter sing a merry song.


#13

I’m thinking of starting a radiation themed band called The Alphas.

I really want to get some vaseline glass at some point, something with a hollow base that can accommodate a UV LED, I just haven’t thought of what should go on/in it.


#14

Do it do it doooeeeeeeet! :smiley:

You can achieve a similar effect with the fluid from a green glowstick (can be even a spent one, the light emitting molecules aren’t consumed and fluoresce on UV).

Real vaseline glass should be available on eBay.


#15

I have a vial of Rhodamine B suspended diethylphthalate, so I basically already have that (leftovers from a cyalume reaction). The glowing is cool, but having it come from something with U in it is cooler.


#16

Yes, that’s pretty much the content of the glowstick.

That’s certain! :smiley:

You may be able to source some uranium glass cullet on eBay. If you have a suitable kiln, you can then make yourself anything from the glass you have tech for.


#17

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