Coal tar pitch

[PabloPicasso]

Anyone got experience of using coal tar pitch?

I have a few questions, although It's not a boaty use that I want it for.

My aim is to use pitch as a pipe bending aid to bend a trumpet bell from straight (the usual way trumpets are) to bent upwards (a la Dizzy Gillespie).

Fill the pipe/bell with pitch and then bend the pipe around a form, and hope the pitch prevents deforming of the roundness, and prevents creasing etc. I'm hoping to get a couple of cheap old trumpets on ebay to practise on.

Any advice on how to use the pitch is what I want. Particularly to stop it sticking to the bell, and what temperature to heat it to to empty the bell after bending.

I've reported this on the wooden boats forum. Maybe they'll have more relevant experience


Thanks

 

[Seajet]

Don't people fill pipes with sand for bending purposes ? Seems a darn sight easier to remove afterwards than pitch, which I must say I haven't heard of being used for this purpose.

 

[PabloPicasso]

Yes fine sand could also be used, And a lot easier and cheaper to come by than pitch. My concern was that sand was less likely to prevent deforming and creasing.

I'll have to get a cheap trumpet first, and then have fun experimenting a bit.

A winter project if ever there was one!

In factory production they use soapy water chilled to about -47'C. Not an option at home. How cold can a domestic freezer get?

 

[vyv_cox]

That's only a little above dry ice temperature, -78C. Widely available.

 

[NormanS]

I've used sand successfully, to bend pipe, never trumpets. I can't think of any advatage of using pitch. Surely in its liquid state, it will behave much like any other viscous liquid.

 

[PabloPicasso]

I've used sand successfully, to bend pipe, never trumpets. I can't think of any advatage of using pitch. Surely in its liquid state, it will behave much like any other viscous liquid.

Have you been successful in bending with no deformation/flattening or creasing of the pipe? Any tips for success?

 

[NormanS]

Have you been successful in bending with no deformation/flattening or creasing of the pipe? Any tips for success?

Short answer, yes, BUT the fine sand must be absolutely dry. (Think tray in oven). It should be packed in as hard as possible, and plugged at each end, then apply heat. However, presumably your trumpet is brass, and heating brass to assist in bending is dodgy. There is a very small temperature range between being hot enough to help, and melting. Have fun.

 

[vyv_cox]

However, presumably your trumpet is brass, and heating brass to assist in bending is dodgy. There is a very small temperature range between being hot enough to help, and melting. Have fun.

Brass tube is going to be 70/30, a body-centred cubic structure same as copper, so very ductile and malleable. It should deform cold just as copper pipe does but could need annealing if it work hardens.

 

[ripvan1]

This thread advises (post 2) against using lead/pitch - having splashed hot bitumen on my hands, I can only suggest you use caution if using it - it was very very sore, stuck like s888 to a blanket, and a hospital visit was required. Lord knows what it must have been like to have been tarred and feathered.


http://www.trumpetherald.com/forum/viewtopic.php?p=1227498

 

[pampas]

I think you will find that most pitch varieties, go brittle when cold and possible deform the tubes that you are trying to bend. I stand to be corrected.

 

[PabloPicasso]

Baked dry sand it will be then. Thanks for all your suggestions. But first to find some very cheap trumpets to work on