A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Robert Swartz
Date: 2015 Dec 28, 14:50 -0800
In the States, flake shellac is practically unobtainable. However, multiple rings of clear liquid painting shellac seem to work.
Teflon O rings seem to work best when obtainable.
Perhaps you can post a source for Viton O rings.
Overall, in my estimation, the best general bubble fluid which can substitute in most bubble sextants is Dow Corning silicone fluid.