I am not sure what kind of glass arrangement you are working with, but in garden variety firings, 0243 Translucent should not completely opacify. (The process temperature I have in mind as I write this is 1480 F, held for 10 minutes.) It was actually designed for use in light shades. In fact, once upon a time, we called this style "Lighting White" but changed the name to Translucent White to make its character more understandable.
Try making a tile using a similar process time and temperature as I described, and see if that level of opacity works for you. If it is too dense, you might want to try Opaline 0403 instead.
Let us know the results of your testing!
Mary Kay Nitchie
Bullseye Glass Co.
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