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Is there a lubricant suitable to put on valve cap threads, to prevent them from seizing over time? It could be very helpful, especially on bottom caps where gunk tends to collect, and can sometimes be difficult to reach.

I've used Never-Seez for automotive purposes, but I'd think it's kinda messy to put on a horn.....

I'm fairly sure my repair guy put Vaseline on my valve cap threads - top and bottom.

Feel free to tell me I must be wrong!

He also advised me to move them each time I play - just loosen them a quarter turn, then tighten back up.

Seems to work so far!

I have not tried this myself. But, I wonder if you could use a wrap of Teflon plumbing tape. I've heard that it works on modular mouthpieces.

Try a food grade anti-seize, Loctite is a brand you can probably find.

I used to use Vaseline until I learned it is hydrophilic and can make things worse over time. I use the same lubricant that I use on my tuning slides that are the "fixed" slides (as opposed to "riding throttle" on the 1st valve slide. And which one do I use? Well, it could be any one of a few different ones that came in the cases of other used brass instruments I have purchased in the last year or two.

Pick one. Anything is better than dry threads, or worse, threads with condensation instead of lubricant.

When I reassemble any brass instrument after chem- cleaning... I apply just a very small dab of the same grease I use for slides... 'Super Lube synthetic grease. It COULD migrate into the pistons or rotors if the valves aren't oiled regularly. However... as Bloke pointed out... those of us who work on stuff daily know that stuck caps usually don't present a problem.

I don't always use lube on my valve caps, but when I do it's silicone grease like

https://www.amazon.com/Dow-Corning-Vacu ... B001UHMNW0
(which I use regularly for slide grease)

or

https://www.lowes.com/pd/Aqua-EZ-O-Ring ... gL_IPD_BwE

Thanks for all the replies -

Generally speaking, frozen caps don't present a problem that can't be remedied by a small rap with a rawhide mallet - I'm thinking of a certain application where space is tight, and access with a mallet might not be possible. I thought it would be small insurance to put something on the threads that would prevent them becoming frozen in the first place.....

At the beginning of every playing sessions I unscrew the bottom caps a half turn and lightly screw them back. They will never stick. No lubricant.

I also pull the slides out to their playing position. It's part of my standard routine for every session.

At the end of the session I push the slides back in, and oil the valves. The top caps don't stick, the slides move freely.

I'm not recommending this procedure for anyone else. I understand some people are too busy.

Hup