Build up of Lead in Mold Cavity

[tecdac]

Did not want to hijack another thread about buildup on mold faces.
Anybody experience buildup in the mold cavity?

This only happens with one set of molds.
My theory is that I cleaned them a little too vigorously. Brass brush.

Disclaimer
I run a Magma Bullet Master.
I'm producing 15k per day.

[Conditor22]

Where is the lead building up? Pictures would help http://castboolits.gunloads.com/show...es-using-IMGUR

can you see light through the mold when closed? - my thought is one or both of the pins moved a little and is stopping the mold from closing all the way
option 2 you got a splash of lead in the mold while it was open
warped somehow -- not likely

[BK7saum]

I have had my brass MP molds "tin" in a couple locations near the lube groove area. I assume that this is a hot spot and a high tin alloy binds to the brass in that location.

[tecdac]

Tried the Imagur thing.
Wasn't able to do it on the phone but looking at the photos I see the roughness of the cavity.

Anybody know how to smooth that out?

[Dragonheart]

You didn't mention what material the blocks are made of; my rule is never uses anything harder to clean a mold that the block material it is made of.

Regardless, I would mix up a thimble full of 50/50 household white vinegar & hydrogen peroxide. This makes a very mild solution of peracetic acid and like all acids will rust ferrous metals. Rub the lead deposits with the mix and a Q-tip, toothbrush or pencil eraser, until the lead deposits dissolve. Then wash with the mold with Dawn dish soap, rinse & dry. I would then completely color the cavities with #2 pencil lead the brush off the excess with a clean toothbrush. Coloring the face of the blocks and sprue is also a good idea as the graphite will inhibit future lead from sticking and also acts as a lubricant.
I graphite all my molds before I cast as it improves the look of the bullet surface and allows me longer casting sessions before having to clean my molds. Those tiny alloy deposits can keep the blocks from completely closing and compound the problem of out of round bullets.

[blackthorn]

When we use this mix to remove leading, in dissolving the lead deposits, it produces lead acetate which is extremely poisonous. Hydrogen peroxide raises the lead valence from zero to plus two, so that a minus one from the acidic acid ion initiates a rapid lead ‘rusting’ process, making grey colored lead acetate which is not sticky and therefore bubbles out. It cannot be stressed strongly enough that this grey liquid is pure poison, so do this well away from areas where food is (or ever will be) grown, prepared or stored and wear rubber gloves. Lead Acetate is absorbed through the skin very easily! This means any contact with the skin can easily result in some degree of lead poisoning. This solution will work, just use common sense with regard to your personal safety.

[Dragonheart]

By all means safety precautions should be taken. Everyone even considering casting should realize handling lead is a very dangerous hobby made even more so by the melting & casting process. Even shooting has risk of lead exposure as high levels of lead dust can be found 50 to 75 feet back from the impact area.

[tecdac]

Molds are Magma.
I believe they are steel.

[dkf]

I like to soak the cavities with Hoppes #9 on a q-tip. Let it sit for a little and then use the lead of a mechanical pencil to scrape off the lead pieces. The Hoppes seems to help the lead lift easier. The lead is soft enough not to scratch the cavities but stiff enough to push the lead loose.

[Dragonheart]

Problem is some of these deposits are so small and get so polished into the surface that scraping them seems to just polish them out even more. When left they tend to pick up more lead and that is the reason I completely remove them. Every time I post the suggestion of the "MIX" someone always jumps in with Lead Acetate. I admit I am not a chemist, but it has been my understanding lead acetate is made in a boiling process.

But lets say you made up a thimble full of absolutely pure acetate, would that be any more hazardous to handle than what you are doing in the day to day casting process? You are working with a very hazardous substance "Lead" and should already be taking precautions to avoid exposure not just for yourself but for everyone. If you are not aware of the dangers of this hobby I would suggest stopping until you do.

Did you know that the use of "Lead" is now what they think was the main cause of bringing down the Roman Empire?

[waco]

When the mold is HOT use a clean cotton Terry cloth to wipe it off.

[38-72]

Has anyone tried an ultra-sonic clean to remove the deposit?

[JonB_in_Glencoe]

I have successfully used a bamboo skewer and a tiny amount of beeswax to remove Lead deposits (tinning) from the mold face on a HOT (operating temperature) brass molds and a Iron mold.
I can't imagine why that procedure wouldn't work on Lead deposits in the Cavity of a Iron mold.

When you remove all traces of Lead deposits, I would recommend doing something to put a patina on the mold cavities. Heat cycling it 3 or 4 times should do it. While I am not a fan of Mold release sprays, If you have a chronic Lead deposit issue with one particular mold, it surely would be one thing to try.

[Dragonheart]

Has anyone tried an ultra-sonic clean to remove the deposit?

The ultra sonic alone doesn't work on removing the lead.

Ultra sonic will significantly speed up things like Evapo-Rust, etc., but the liquid usd in the bath has to help it along.

[owejia]

A shout out to Dragonheart about the #2 pencil lead [graphite] mold treatment. Works better than anything I've tried. Used a carpenters pencil because the lead is so wide.

[Dragonheart]

A shout out to Dragonheart about the #2 pencil lead [graphite] mold treatment. Works better than anything I've tried. Used a carpenters pencil because the lead is so wide.

Glad it worked for you, thanks for your reply. I also use the wide pencils on the flats and sharpen the standard to a fine point to get into the bands. Not only does graphite eliminate sticking bullets and most of the small lead deposits, the fine graphite rubbed into the grain of the iron leaves a smoother bullet surface. Not to mention no oil contamination in the cavities. It works on iron, brass or aluminum blocks.

[McFred]

Maybe it was a sticky on the forum here but I dissolved out the lead with vinegar that built up on a brass mould I had. I took a piece of fresh-cut brass and tossed it in some vinegar to see if it'd damage the brass. After a few hours, it didn't tarnish or anything so I went ahead and used cotton balls soaked in vinegar in the affected cavities. I know it makes lead acetate. I know it's bad for you and is skin-permeable. I didn't eat it or bathe in it.

Thanks for the graphite tip. If it prevents future tinning build-up then it'll save the trouble of having to clean out the cavities again.

On cast iron moulds, vinegar will remove any black oxide finish if you care about appearance.

[Dragonheart]

Maybe it was a sticky on the forum here but I dissolved out the lead with vinegar that built up on a brass mould I had. I took a piece of fresh-cut brass and tossed it in some vinegar to see if it'd damage the brass. After a few hours, it didn't tarnish or anything so I went ahead and used cotton balls soaked in vinegar in the affected cavities. I know it makes lead acetate. I know it's bad for you and is skin-permeable. I didn't eat it or bathe in it.

Thanks for the graphite tip. If it prevents future tinning build-up then it'll save the trouble of having to clean out the cavities again.

On cast iron moulds, vinegar will remove any black oxide finish if you care about appearance.

Vinegar is very slow to work so if you make a 50/50 mix with white vinegar and standard 3% hydrogen peroxide it will work much better and a lot faster. Use caution in handling.

[McFred]

Thanks, I'll keep that in mind the next time I have to clean out a mould.

[JimB..]

I use the dip when cleaning some suppressors, but I question its utility for cleaning molds. Isn’t what’s really “sticking” the growth of a tin crystal rather than lead? The dip won’t dissolve tin, for that you need things that are far more dangerous.

Thanks for the graphite tip!