Use of Sal Ammoniac block

A block of sal ammoniac is an excellent aid to keeping your soldering iron tip (or bit) clean and able to hold a small blob of solder.

A description of what sal ammoniac is and the safety precautions in its use are here. 

• Place the block in such a way that it cannot slide around as you rub your iron over it.
• Place your hot soldering iron tip on the block until it begins to smoke. 
• Move your iron slowly back and forth along the block.  Initially, the block will be black from the contaminants coming from the soldering iron bit.  As you rub the bit along the block, it will begin to clear. As it does, you can add a touch of solder and turn the bit over to check whether there are still any black spots on the face of the bit. 
• If these spots are persistent, you can use a brass wire brush to help clean the contaminants off.  
• Add a touch of solder and return to rubbing along the block.  
• Repeat this check until the whole bit is bright and holding a small blob of solder.  
• This completes the tinning process on one side.
• Repeat this process for the other side too.
• Leave a small blob of solder on each side of the bit to protect the bit from oxidising.  

This cleaning process should be done at the end of each soldering session if the bit is not clean.   The frequent quick wipe of the bit on a damp sponge or a ball of brass swarf cleans the bit as you work.  The sal ammoniac block is for cleaning persistent contaminants off the bit.

Soldering old lead

This is normally only a requirement when repairing old windows. Usually either to join new lead to the old, or to repair breaks at the original solder joint.

You will need to clean the lead down to the bright metal at the joints. This is more than a rub with steel wool. You need a glazing nail or other sharp pointed tool to scratch through the oxidisation layer.  The corner of your lead knife, or in cases of mild oxidisation, a brass wire brush might do. But not a steel one, as that may scratch the glass and any painting.  

Do not clean the oxidisation off the lead elsewhere. That is a protective layer already formed which leads to the longevity of the came. It is best to leave oxidised lead alone rather than expose the metal to further oxidisation.

Getting to the bright metal where you want to solder the joint means the flux can act appropriately and help the solder form a secure joint.  Otherwise only a weak, cold joint is possible.

Note that you always need to use dust masks or other breathing protection.  You need to have the work area well ventilated and need to do a damp wipe down of surfaces to reduce the amount of lead oxide in the work space.