(07 February, 2001)
Circumstances obliged me to notice that it's possible to make ruby in an ordinary kiln, if you're willing to tolerate it being a powder rather than large chunks. (I can't get hot enough to melt the stuff, but it turns out that you can make it well below its melting point if you do it the right way. There are even several right ways.)
At any rate, last week I did this thing, and then I decided to attempt to incorporate it into a clear glaze. The result is something I can only describe as a "pink celadon", though of course that's a contradiction in terms. Celadon is gray-green. It's also, as far as I'm aware, supposed to be somewhat milky, because it's supposed to look like jade, but that's another story.
In any case, here's a photo of my ruby pink glaze. I was
obliged to shine a red light on the bowl to bring up the
color of the glaze because the general illumination was,
unfortunately, fluorescent; and I didn't want to mess
with the image on the machine any more than I had
to. It's enough of a pain to create the various sizes.
(07 February, 2001)
Clearly, there are quite a few things that can make
J. Random Glaze appear pink. Just so you'll know that
this is what I say it is, here's a photo under
blacklight. I must apologize for the lousy focus -- my
camera is in serious need of repair, and on top of that
I was in a bit of a rush. The deep red color is the same
fluorescence that is used in the ruby laser, and is at
694.3 nm. No, I haven't actually measured it yet. Yes,
I'm relatively confident that what's making this
particular glaze pink is ruby dust.
(07 February, 2001)
One of the other tests on that same bowl was a plain
zinc silicate crystal glaze, which I activated with
about 1% Mn. This results in synthetic fluorescent Willemite:
Please ignore the blue speckles -- they're just lint. Please also ignore the purple, which is the camera picking up rather more of the UV than I'd really like.
That's about it for right now, though I am pleased to
report that I'm working on ruby with higher chromium
concentration, so I can darken the glaze.
(10 February, 2001)
When it became clear that the first batch of powder wasn't dark enough I made up a second batch, with just about 4% Cr. When I popped the kiln open, just after firing it, I was somewhat dismayed to observe that it was distinctly gray, as if only part of the chromium had been incorporated. Oh, well... Let's just leave this in for the next firing, shall we?
Yesterday I looked at that second batch of powder again, and was surprised to find it pinker than I remembered it. Hmmm. This is decidedly not the kind of reaction that is going to proceed at room temperature, so what gives here?
I stirred the stuff up, and ran it through the kiln again last night. Sure enough, when I opened the lid this morning it was gray. Assuredly, chromium in solution in alumina is _not_ going to fall back out by magic, so at that point I decided it might be some sort of truly weird temperature effect. I chilled a bit of it, and sure enough it turned pink. (Well, a slightly grayish magenta sort of pink, but certainly much lighter and brighter than it was while it was hot.)
If I have time, I will try to investigate this effect. In the meanwhile, however, I added some rubbing alcohol to the stuff and boiled it in the Lab microwave ("Nhot for Fhood!") on the excellent advice of Scott Scidmore, who points out that hexavalent Cr (which is noxious) will oxidize alcohols, in the process taking itself back to the relatively nontoxic +3 state.
The microwave decided to get into the act, and provided one of those little superheating incidents. Fortunately, only a modest proportion of the stuff is now splattered all over the inside of the oven (grrrr), and I retrieved the rest. The supernatant liquid was yellow, and I am not at all sure what that signifies, other than the fact that very clearly there was a little bit of _something_ beyond just ruby in the reacted powder. In any case, after a few rinses the liquid came off relatively uncolored, and I'm now drying my rubies so I can throw them into a glaze. I'll clean the microwave later. Argh.
I don't have a photo of the new powder yet, but when I do I'll put it here. It is not unattractive...
...but it doesn't fluoresce much, unlike the stuff I
made the first time. This is not uncommon -- as you
increase the concentration of the dopant, often you find
that the fluorescence peaks and then decreases.
