Fused flux

In spite of searching the archives I haven’t been able to find a fix
for my problem. I have managed to fuse flux in an area that is
recessed but will be visible so it has to be removed. It is difficult
to get into the area which is small but noticible. I have done
everything I can think of to remove it but have had no luck at all.

It is difficult to get into the area which is small but noticible. 

Ultrasonic? CIA

In my experience, fused flux only comes off with longer pickling.

Judy Bjorkman

In my experience, fused flux only comes off with longer pickling. 

I had some flux in a chennier, and it would not shift no matter how
long I left it in the acid.

Chucked it into the ultrasonic, and it shook loose.
Regards Charles A.

I had some flux in a chennier, and it would not shift no matter
how long I left it in the acid. 

What kind of pickle are you using, and how hot? I’ve had tube filled
entirely from one end to the other in an inch long small diameter
piece clean up nicely. Took an hour or so, with fresh sodium
bisulphate pickle at a simmer just below boiling…

Oh, and I do have a steam cleaner which helps remove stray bits of
debris that might still have been in there, but poking a wire in
would have worked too.

If, instead, you’re using weak citric acid pickle, and using it
cold, well, you might have a problem…

Peter Rowe

Hot water removes flux. The acid in pickle removes scale, oxides,
etc. Soak it in boiling hot water.

Cynthia Eid

Theoretically, it is best to remove flux in plain old boiling water
before pickling in acid. I tend to skip this step if the flux is
minimal, but with pieces that have a heavy coat, I always boil it
off first—keeps the pickle cleaner. If I do boil first, I heat the
piece again slightly before putting it in the pickle.

Janet in Jerusalem