ART OF STAINED GLASS
There is one hazard that stained glass artist must always be aware of. This is the dangers of selecting glass according to color, and not minding the delicate balance of the various levels of transparency in their composition.
For lampshades, Uroboros, Bullseye and Youghiogheny glass are generally considered the best choices because they they have just the right balance of opalescence (opacity) and transparency. Spectrum glass, for example, tends to make lampshades that are too "dark." Bear in mind that mixing Youghiogheny glass with the glass of other manufacturers within a lamp shade is quite risky, because of unique properties - it tranmits the most light, yet reflects the least. In other words, when the shade is unlit, the glass looks very dark and near black, because little light is reflected off the surface. When the shade is lit from within as with a light bulb, it transmits the most, that is, the pieces of glass appear considerably brighter than other manufacturer's. If you decide to mix Youghiogheny with other glass, you have to be sure that you want the Youghiogheny pieces to be strikingly brigther than the rest.
Take a close look that the image below. White glass with different light transmission/reflection properties has been used for the flowers, and for the background. The flowers use the glass with the greatest amount of light transmission and least amount of light reflection. This white glass is Youghiogheny SP-1000. The white background used 1000 HSL which has properties opposite of the SP-1000, namely, it reflects more light, and transmits far less. Compare this "white-on-white" effect when the window panel is back-lit or front-lit.