More loosely relates to these issues: MC-144009 MC-145821 MC-164001 MC-165403
The bug
If translucent pixels are present in any of the three UI sprites brewing stands use, they are rendered completely opaque in-game, which is not correct.
The bottle textures are baked into the UI for some reason rather than being separate sprites like all other outline-type textures (MC-74408), and as such are not included.
How to reproduce
Download and apply the attached resource pack
Start brewing
Observe
Expected results
Translucent textures where the fuel, arrow and bubbles would be.
Actual results
Entirely opaque.
Linked issues
relates to 12
MC-109447
Inconsistency in transparency of GUI PNG files - only some can be transparent + hover-bugs
Resolved
MC-144009
Particles no longer support translucency
Open
MC-145821
Stained glass, ice, slime block and other transparent block particles are not transparent anymore
Resolved
MC-164001
Some textures no longer support transparency
Open
MC-165036
Boss bars with the notched style are rendered incorrectly if more than one boss bar is active
Resolved
7 more links
Can confirm.