For many years men dressed solder irons and once true, use the rubber
on their shoe (inside of the heal) to coat all the tip except the
wetting location.

I've also used rubber erasers that I heat up with a heat gun and then
wipe over areas.

Modern workers don't need to worry - the joint is small. But they make
resists that you can paint on. Just like solder resist used on printed
circuit boards.

I'd think on some items it might be best to use High temperature (glass)
tape. Woven glass. or Fiber glass with glue on the back.

I think you can buy resist at local Radio Shack stores.

Martin

On 3/13/2011 4:48 PM, Cydrome Leader wrote:
What's a good way to keep solder from flowing or wetting copper or brass
parts being soldered- sort of like an anti-flux. I recall seeing something
posted here about it, but can't locate it.