Stained Glass only translucent when particles on-screen; otherwise transparent

Using custom Glass pack for visibility and colour.
http://www.reddit.com/r/Minecraft/comments/1o9fya/retextured_stained_glass_opinions_top_blue_is/ccq8zsq

Steps to reproduce:

1. Place Stained Glass Block, Stained Glass Pane, etc.
2. Set Particles to Minimal.

Note: Setting Particles to Minimal is not required; a no-particle environment will work just as well.

Tips:

Try placing a Torch (or other particle-producing block) near glass panes; note change.