Dave it helps to have 38 years in U.S. glass, 22 of which as an NCC member. I don't wish to hijack this thread, however sometime I'd like to discuss with you the 1%-2% of Uranium needed to produce reactive glass in a batch especially a batch as small as 50-100 lbs. I have reviewed some of the Cambridge glass formulas for reactive batches, large batches of over 1/2 a ton & these are from Henry Helmers (America's glass chemist) book. Now there is a codicil of what I'm about to say & that is its entirely possible that todays UDs are not anywhere of the same strength/power of those used in the 19-teens through around 1960. Having said that this is the formula for Cambridge Light Emerald which many call (right or wrong) Vaseline. Cambridge Light Emerald Chemical Formula:Sand 850 lbs, Soda 330 lbs, Feldspar 100 lbs, Lime 42 lbs, Nitrate 50 lbs, Lead 36 lbs, Arsenic 10 lbs, Copper Oxide 13 oz, Uranium 43 oz.
This is a 1,358 lb batch & you can do the math. The salts/UD used to produce the reaction of a 1,358 lb batch is in the tenths of one percent. You mention Topaz, well its higher, but still is only 7/10th of 1% for a large batch. I'm simply wondering if the 1%-2% U salts figure has been repeated for so long that people simply accept it rather than looking at company batch formulas? Helmers worked for Cambridge, Heisey, Fostoria, Economy, Morgantown, Erickson, etc. just to name a few over his lengthly career & his book covers several thousand glass color formulas. It would seem that nowhere near 1%-2% in the vast majority of cases (based on batch weight) of salts/UDs was necessary to produce reactive glass, at least not from the 20s through the 60s, but again I there is not a "strength/power" indication of the chemicals of that period to compare them with the same chemicals used today so who knows? Just a thought. Ken