I'm an instructor at Bullseye and have incorporated silver foil (the sheets that we sell here) into a few of my workshops. I tend to fire it with French Vanilla and other styles that have reactive potential with silver. Look for sulfur bearing styles in GlassTips http://www.bullseyeglass.com/education/glasstips/
as well as Reactive Ice clear and Reactive Cloud opal. Effects vary with different glasses, lay-ups, firing schedules, etc and may also change with multiple firings - there's great potential for exploration. I'll post again tomorrow with a bit more detail and a photo or two.
It sounds like you've experienced the yellowing that often occurs in a full fuse when fired in contact with clear, whether the silver is on the top layer or capped. This is typical and I've seen it look especially thin and yellow (as you've described) when the silver is fired on the top surface, uncapped. In my samples, Crystal Clear has produced a similar result.