Getting lead off of mould blocks

  • Last Post 17 September 2022
jtcarm posted this 09 September 2022

I got a little too eager breaking the sprues with a set of aluminum blocks the other day and have a little lead keeping the sprue plate high on one cavity and causing fins.

What’s the best way to get it off?

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Ross Smith posted this 10 September 2022

There's only three ways that I know of and they all require that you be careful. razor blade, steel wool, heat.

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Bud Hyett posted this 10 September 2022

Assuming the lead is on the top of the mold: :

  • Carefully scrape with a new razor blade at a slight angle. Do not force.
  • Lead removal cloth. Then wash the surface to remove the chemicals
  • Do not use Ed's Red, or similar, to loosen the spot, seems like forever to get the oil out of the cavities. 

If the mold has sit for several days, you might get it off with a fine brass brush. 

As a precaution with a new mold, I slightly deburr the edges to about a .010 radius to allow the sprue plate to seat flat. Then I periodically check the edges for burrs that would hold the sprue plate up. I have worked too fast and burred the edges that holds up the sprue plate on closing.Then you get finning or even lead on the top.  

Farm boy from Illinois, living in the magical Pacific Northwest

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Rich/WIS posted this 10 September 2022

If you have a hotplate preheat the mold enough to liquify the lead and wipe off with a NON synthetic piece of course cloth.  When done de-burr the bottom of the sprue plate and top of the mold (light polishing with 400 sandpaper).  Plug the cavities and lightly spray mold release on the top of the mold and bottom of sprue plate, When dry wipe off excess.  Keep an eye on it when casting and wipe off any lead before it builds up.

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Duane Mellenbruch posted this 10 September 2022

Well, here is just one more opinion to consider.  Sounds like enthusiasm got ahead of things so I am going to suggest something a lot less aggressive.  It is not clear to me if the lead is stuck to the sprue plate or the mold block.  I would discourage using anything aggressive around the sprue cavity to avoid reducing the sharp edge of the mold, which will then cast fins at every cycle.

A small soldering iron with a little solder on the tip can be used to apply heat just to the spot of lead on the mold.  This will soften the lead and allow it to be scraped away with a small pointed hard wood stick.  Then wiped clean with non-synthetic material.  Be patient.  It takes little effort to mess up a mold, and so much more effort to repair unintended damage.  Good luck.


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Tom Acheson posted this 10 September 2022

This works well for mold blocks and sprue plate surfaces. I do it at the end of every casting session.

While the mold is hot use a small piece of Birchwood Casey Lead Remover and Polishing Cloth on the “contaminated area”, scrubbing on the area back and forth using one of the edges on the end of a square wooden stick. The cloth is dark white or yellowish in color.

An old suggestion given to me said to use Zudd cleanser and an old toothbrush on a cold mold. Some people use the Birchwood Casey product to TRY to clean the face of a revolver cylinder. Seems like it never comes completely off though.



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sluggo posted this 11 September 2022

I have had luck using desoldering wick. It is braided copper wire. Put it on top the lead and apply a large soldering iron. It should wick on to the braided copper.

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fc60 posted this 11 September 2022


Casting today and sure enough, I got a small Lead smear near one of the cavity edges.

To remove it, I used a one pound LinoType ingot and rubbed the mould where the Lead was.

It came off readily. Sort of like using an eraser.



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Eutectic posted this 12 September 2022

I use a sharp  3H or 4H art pencil. These are harder than any lead alloy but softer than the aluminum block and will scrape off the deposit. Then I use a 6B art pencil (very soft) to leave a graphite coating which helps prevent alloy from sticking.

You can use the pencils on a hot mold while casting. This is actually easier as the alloy is softer, the graphite pencils are unaffected by heat.


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Qc Pistolero posted this 12 September 2022

lead removes lead.I use the sprue from a 4 cav mold(it is longer;I got more leverage from it) and rub it against the lead smear..But I now rarely have the problem since I put some 2 stroke oil under the sprue plate,on top of the blocks and at every friction points of the mold.Use very sparingly more so on top of the blocks.While that won't prevent lead smearing if overenthousiastic,it will make lead more easily removed.

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Duane Mellenbruch posted this 12 September 2022

Just to make it a bit less confusing for the OP.  He was starting with lead on a cold mold.  This has drifted a little and has been talking about lead removal from a hot mold while casting.  That does give a lot of options for the  OP or others to try.

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Shuz posted this 12 September 2022

I have found that a rough leather glove rubbed on the hot mould or sprue plate will easily remove the lead smear.

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Alstep posted this 17 September 2022

I found that a sharpened carpenters pencil works good to scrape off lead smears.   Doesn't harm the mold in the least.  I also give all the mold surfaces a coating of graphite with the pencil to prevent more leading of the mold.  That includes the sprue plate too.   I do this every time I refill the pot while I'm waiting for it to melt.   Haven't had any leading problems on mold surfaces since I started doing this.  

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jtcarm posted this 17 September 2022

Hot mould + leather welders glove did the trick.

Now I’ve got a couple of sticky cavities to contend with.

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