Where on earth did you get uranium pentoxide??? That really must have been a long time ago! Earlier this year, I searched for it extensively over a period of several weeks, and the only source I could find wouldn't sell it to me as an individual, and only sold in huge amounts like hundreds of pounds. I read in an old text about what a great yellow color it could give at high fire temps (cone 10...).
What cone(s) did you fire it at?
Sorry...terraforma.... I wasn't using the uranium pentoxide in ceramics or glazing. I (as a grad student -1986) was given two pounds of the oxide by my instructor while at NYSCC (Alfred). He had used quite a bit on a large lead crystal sculpture in previous years, and this was his leftover. I used it to batch up 200 pounds of borosilicate glass for some sculpture work I was doing at the time.
This is one of the pieces I was working on at the time.
It traveled to Japan and then found its way to the Glasmuseum
at Ebeltoft, Denmark, where it resides today.
The bright yellow is the uranium pentoxide batched into a lead crystal glass and the darker green is the oxide batched into a borosilicate glass.
Though it does register a little activity on a geiger counter, according to Corning Museum of Glass, it is a very low amount (less than one X-ray/year or something like that).