Is there an opposite of soldering flux?

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PaulUszak

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This is a bit of a curve ball.

Is there a substance that can be applied to copper to prevent the spread /adhesion of solder? So if you apply this stuff, the solder would be repelled and the copper remains clean? Sort of a masking fluid /tape that withstands a blow torch. Anything at all?
 
Solder will not stick unless the copper is absolutely clean, hence the need for flux in the first place. Copper will naturally develop a patina over time, if you really don't want solder to stick anywhere else, then don't clean the pipe any more than than you need to.
 
You could try "Snopake" or similar. Its supposed to work but I've never tried it.
 
Traditionally what was used by plumbers and model engineers to prevent solder sticking where not wanted was plumbers black. You paint it on the pipe then scrape it back to a straight line and the solder won't stick to the black stuff.

Unfortunately I don't think it's widely available any more. It is easy if time consuming to remove dribbles of solder with wet and dry paper.

There are a number of solder resists used for PCB making these can be found on Amazon etc. I don't know if they can be used on pipes.

Hope this helps.
 
Cean and flux your fittings. Attach fittings together and wipe of any excess flux.

Solder only runs where the flux is.
 
PaulUszak said:
that withstands a blow torch
Click to expand...

That’s the hard part. Out of curiousity I just checked the spec for an electrical solder resist and apparently it is designed for 275 C max.

As above, apply less flux, wipe off excess flux before heating, apply less solder.

Or use solder ring fittings - that’s what I’ve been doing and I get the opposite problem, they seem to have so little solder in them that the amount that appears at the end is visible only with a microscope; as a result I end up heating for longer than necessary.
 
It's the flux running out of the joint and down the pipe that takes the solder with it. I use laco but have heard some use a less runny flux to combat this problem.
 
Bill RE said:
Traditionally what was used by plumbers and model engineers to prevent solder sticking where not wanted was plumbers black. You paint it on the pipe then scrape it back to a straight line and the solder won't stick to the black stuff.
Click to expand...

Might plumber's black be like:-

81YtKztW9cL._SX679_.jpg
?
 
never use flux inside a fitting, only on the pipe and the less the better and always wipe off after , and never brush a finished fitting with flux what is that all about ???
 
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