(1999)
I have been looking into activating some glazes with rare-earth elements (so-called — they aren’t really all that rare, just difficult to separate from one another). Here is the first half-decent photo of my early results. I say half-decent because the object on the left should be distinctly orange, the object on the right should be brighter, and the one in the middle should be bluer. Unfortunately, it looks like some of the UV got through the filter and lens, and so the color-balance of the photo is messed up. In addition, my scanner is maybe not the best in the world.
(Since I did this work, I’ve gotten both a better
scanner and a digital camera. Life is good.)
July 4th, 2000...
I have now tried a number of elements, of which the most promising are Tb (terbium, yellow-green), Tm (thulium, deep blue), and Eu (europium, vastly the best thing I’ve tried so far, bright sky blue in my clear glaze if properly reduced or pinkish if only partly reduced). I have read that reduced Eu can be just about any color, depending upon the matrix that it’s in; so far I’ve only tried it in two of the members of my clear glaze family, and it seems to be sky blue in both of those. Sm (samarium), Dy (dysprosium), and Ce (cerium) also work, but seem, at least so far, to be less bright.
Here’s a photo that will let you compare the clear glaze
by itself, the clear glaze with 2% cerium oxide, and the
clear glaze with 2% europium oxide. I should point out
that this is not as good as it gets — I used the
"ordinary" version of the glaze, over regular commercial
throwing porcelain, which is not going to give the same
kind of performance as the slightly fancier version over
real whiteware; also, if memory serves, Eu works better
at 5% concentration than at 2%. (I will, I hope, be
confirming that fairly soon.) Note, by the way, that
this photo was taken in dim daytime room light. I tried
taking it in the dark, but the europium was so bright
that it showed mostly as white. In addition, the tile on
the left was invisible. Allowing some room light seemed
like a viable compromise — it really gives a sense of
just how bright the fluorescence is.
——————————————————
Here’s a photo of the same three tiles (clear, clear
w/Ce, and clear w/Eu) without the UV lamp, in slightly
brighter room light:
As you can see, aside from the corners of the europium
tile (which I redipped and got too thick), the three
glazes appear almost identical under ordinary
conditions. It may not be obvious from this photo, but
the cerium glaze (in the middle) is very faintly
greenish in comparison with the plain clear, as is the Eu.
Just for fun, here is a shot of the same clear glaze,
but with 25% red iron oxide added to it instead of one
of the rare earths:
It’s difficult to see here, but this is partly a black aventurine. I’m quite pleased, because that’s what I was trying for. It’s a bit runny, though, and I will probably have to fuss with it. (It is actually possible that the aventurine spangles will only form in relatively runny glazes. That is common among glazes that form crystals of visible size, in fact.) The black spangles are barely visible, just above the lower margin of the glaze in the middle of the test tile. (They also formed in the two drips, but are not visible there in this photo.)
Lighting for this shot is a combination of the room lights (fluorescent) and a high-intensity white LED, which I didn’t aim quite as well as I would have liked. It’s just about impossible to show the spangles in a single image in any event, so I suppose I shouldn’t be too disappointed.
(20 May, 2001)
Since then, I’ve done
a bit more with aventurines,
and I’m still working on them.
Contact: myfirstname (only 3 letters, please) at myfirstnamemylastname (9 letters, no punctuation) dot org
