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Red Rot / Cracking



 
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PNut
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Joined: 08 Apr 2021
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Location: Canada

PostPosted: Wed May 12, 2021 5:52 pm    Post subject: Red Rot / Cracking Reply with quote

I find it very difficult to determine what is red rot and what isn't. I've read articles and looked at a lot of photos, but it still puzzles me.

Is this red rot and a possible crack? Two Photos with oval over areas of concern.

https://photos.app.goo.gl/hRi3MWqfXWojK2We7
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Goby
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PostPosted: Wed May 12, 2021 6:15 pm    Post subject: Reply with quote

the circled areas on the valve block are surface corrosion/oxidation. There looks to be some red rot on the leadpipe of that horn, however. Red rot happens from the inside out, and is most likely to happen on the leadpipe and tuning slide. These areas are exposed to the most moisture and saliva, and also tend to be where moisture settles when the trumpet is put away. The ends of inner slide tubes can also rot out over time, but since they are sleeved by the outer tube, this doesn't cause any air to leak out. Generally, the metal on the valve block is too thick and not exposed to enough corrosion to develop red rot. Un-neutralized flux from soldering will cause brass to corrode, especially at the joint between balusters on pre-1977 Bachs and on the tone ring of Olds Supers, but this isn't generally considered red-rot since the valve block solder joint and bell rim are not containing any pressurized air the way the leadpipe or tuning slide is. Corrosion on the aforementioned models is more due to workmanship and manufacturing methods rather than excessive use and decomposition of the metal at crucial points. A horn with red-rot can be played for many years before the corrosion breaks through the metal and causes holes/splits to form, but once it starts, it is inevitable that the part will need replacing.



In summary: look for red rot on the underside of the leadpipe and on the main tuning slide. Those will be the first areas to go. The pattern is red dots, sometimes with a dark hole in the middle. It can also cause bubbling underneath plating.
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cbtj51
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PostPosted: Wed May 12, 2021 7:28 pm    Post subject: Reply with quote

The pictured Main Tuning Slide shows bubbling under the Silver Plating from the inside out (place your cursor on the picture and click for enlargement).



This horn was in storage with the bell facing at a downward angle for more than a decade allowing the dezincification to advance to this degree along the lowest point. The complete tuning slide was replaced by Jim Becker at Osmun. There was no red rot in the leadpipe because of the angle of storage. Fortunately this was a relatively easy and affordable fix.

Mike
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Irving
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PostPosted: Thu May 13, 2021 12:00 am    Post subject: Reply with quote

Look down the lead pipe (taking out your tuning crook first) and see what it looks like inside. If you see craters that correspond with wear or pink spotting on the outside of the lead pipe, then that is red rot. If it looks smooth on the inside, then it is not red rot. You can clean the inside of the lead pipe with a brass brush (NOT steel), but if you suspect red rot, then you can damage the lead pipe if you have red rot that has worn the brass very thin.

BTW no red rot seen in your circled areas. Possible red rot in lead pipe.

To prevent red rot (which usually occurs in lead pipe and tuning crook), swab out after playing to dry the horn. You don't want to put the horn away when it is wet. It is a simple solution and takes less than a minute. Just swab out the lead pipe and tuning crook and you are done. Blow the water out of the rest of the horn first.

If you are too lazy to swab out when your are done playing (at home) then pull out your tuning crook and hang it on your music stand so that it drips on to the floor. Then put your horn on a trumpet stand. Let them sit. Both the horn and the tuning slide will air dry.


Last edited by Irving on Thu May 13, 2021 2:49 am; edited 1 time in total
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PNut
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PostPosted: Thu May 13, 2021 1:32 am    Post subject: Reply with quote

Thx!
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Rwwilson
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PostPosted: Thu May 13, 2021 8:53 am    Post subject: Reply with quote

I agree with the other posters about red rot. What your photos are showing is the kind of surface corrosion that is common with older horns. The corrosion is occurring in areas where the lacquer has failed. The larger areas are usually where the horn has been held. The smaller dots are caused by pinpoint holes in the lacquer. If allowed to continue the pin point corrosion will lead to surface pitting of the metal. This occurs in both brass and nickel. Vintage lacquers were not nearly as good as those in current use. In order to stop the pitting all the lacquer should be removed. The horn can then be left as is or re-lacquered or silver plated.
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