A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Paul Dolkas
Date: 2021 Sep 17, 04:34 +0000
Chris & David-
I hadn’t heard about using white spirit in a bubble, but I’m not fun of pickling my brain on Xylene fumes either. They used to specify Xylene because it had the same index of refraction as glass, i.e. 1.5 or thereabouts. White spirit is slightly lower, somewhere between 1.41 & 1.44, depending on the brand (It’s a mixture, so recipes vary). The other commonly used liquid is Isopropanol, which is a bit lower still @1.38.
My question is: does it make a real difference? I’d love to hear anybody’s thoughts. Or is there some other reason for not using anything other than Xylene – do the others dissolve the seals?
From: NavList@fer3.com [mailto:NavList@fer3.com]
On Behalf Of David Pike
Sent: Tuesday, September 14, 2021 8:30 PM
To: Paul Dolkas <email@example.com>
Subject: [NavList] Re: A12 bubble chamber
Chris. You're unlikely to find a spare bubble chamber without paying through the nose and then some. However, there's plenty of advice on here about renovating one. Sharps are available by the dozen from China on eBay for pennies. Just make sure you do it over a tray because if you lose the tiny ball bearing you're really in trouble. Unless you're pretty confident about your ability to seal the chamber 100pc vapour proof, use the least volatile possible liquid to fill it. I used decorator's white spirit. It's sacrilege I know, but you probably have it at home already, and your bubble stays a usable size for weeks if not months. Have a go. You can't make it any worse than it is already. DaveP