Thread: Phosphate Opal
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Old 04-12-2009, 09:18 PM
Dave Bross Dave Bross is offline
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Strontium Carbonate, $1.75 a pound in a 50# bag. If all else fails all pottery supplies will have it. This isn't going to help in New England but I got it from Davens Pottery Supply in Atlanta for less than what the major chemical supplier wanted.

About the glowbars, this stuff is no relation to the radioactive Strontium 90 and not useable as a silicon carbide heating element so I think that covers both possible answers there?

In my E&T spreadsheet I'm using a factor of 1.38 for Strontium to calculate expansion. I had forgotten that it's nearly identical expansion to Barium at 1.40 so there's an easy substitution.
That batch I wrote out will come in at 96 in my tiny melter but will probably be off a good bit in a melter with power.

Here's some from Volf from the Strontium chapter:

"Because of its identical charge and similar effective radius, r1, Sr is sometimes compared with Pb, despite the differing electron configurations of the two elements. The latter are reflected in the different polarizabilities of the two elements and their properties in glass. Pb as an ion of a B-subgroup element with a high atomic weight is twice as polarizable as Sr. In contrast to Pb, Sr with its lower atomic refractivity neither decreases the surface tension nor concentrates in the glass surface. Electrostatic charges therefore are not created on the surface of Sr glass by friction, as is the case with lead glasses. The closeness of the radii of Sr and Pb is responsible for the possibility of replacing considerable amounts of lead oxide in glasses containing 30% of PbO; in this way, Partridge reduced the PbO content from 30 to 20% by introducing 2-15% wt.-% of SrO."

There's more about how Strontium fines/melts better because it fluxes at a lower temp. and puts less gas into the melt than Barium.

Reading between the lines elsewhere in that chapter, Strontium does somethiing odd at over 15%, no particular details there as to what.

Another important point from Volf, Strontium glasses must have alumina in them or they will be less water resistant than calcium glasses.
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Last edited by Dave Bross; 04-12-2009 at 09:21 PM.
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