Brass Mold Oxidation

hporter

Active Member
I have a question about what to do with this?

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This is a Mihec 45 200gr SWC mold that I have had for a long time. I just finished photographing and doing a database inventory for each mold I own. When I got this one out of the airtight plastic container I store my molds in, it had this weird oxidation in the second cavity and a little bit in the fourth cavity.

What would be the appropriate action to take, to try and treat this? I have a bunch of brass molds, but this is the first time I have encountered this.

It was interesting to me, going through all my molds. I was really surprised by the iron molds. Most of them I slather up with 30 weight oil, and store in air tight containers. But the few that I left dry, were in brand new condition with no signs of any corrosion.

What really surprised me were the quantity of aluminum Accurate Molds and NOE molds that had more than a little rust on the sprue plates. The aluminum molds were in perfect shape, but some of them had significant traces of rust on the top surface of the sprue plate that wouldn't come off with a light brushing with oil and some 000 steel wool.

I bought some indicating 5 gram desiccant bags to put into each air tight container. I usually put two molds in each container. These desiccant bags turn color when they become saturated. I am hoping that storing them with the desiccant bags will reduce the likelihood of surface rust in the future.

Thank you in advance if you have some advice on this brass mold. And if you want a fun and surprising time - go out and document every mold you own. You might be overwhelmed at the number of them (especially the quantities of the ones you forgot you purchased)!
 

Bret4207

At the casting bench in the sky. RIP Bret.
Is that like the verdigis (SP?) you get on brass cases sometimes? I think that's caused by a reaction with something that's an acid, but you should probably look it up, or ask the mould maker. They may have experience with it. If all else fails, 4/0 steel wool on a pop sickle stick would be my answer.
 

hporter

Active Member
Thanks - I don't know why I didn't start with Mihec first. I just figured someone on this forum had run into this before.

Appreciate the advise.
 

Ian

Notorious member
A Q-tip soaked with a citric acid solution should take care of it.

When I finish casting with any mould having a steel plate and hardware, I swab a very light film of synthetic two-cycle engine oil on every steel part while the moulds are still hot, then store them on an open shelf when cool.

What I have found is cleaning and oiling moulds needs to be a maintenance routine, just like cleaning and oiling all the guns in your humidity-controlled safe every so often is a routine. Every method of storage and preservation is fallible to some degree and you need to keep an eye on things.
 

hporter

Active Member
Thanks for that Ian. I was hoping for a solution that wouldn't require an abrasive. That is a good mold and I hope to keep it that way.

I hear you on the maintenance routine. That is one of the reasons I built a database of all my molds. It is the only way I can keep track of them in a sensible (to me) fashion.

Now I can add a field for dates used, quantity cast, what alloy and maintenance. That will also give me some degree of an idea of how many bullets I have on hand from which mold. And to be nerdier - I can print a label to stick on the container they are in with those notes.
 

Petrol & Powder

Well-Known Member
I would suggest getting the mold hot and removing the traces of lead. There's a possibility the lead is trapping something between the lead and brass.

After the mold cools, clean it as Ian suggests. Maybe get a little aggressive on the top surface with an old toothbrush but nothing that will damage the brass. Then dry and heat the mold again, coat the steel parts with oil as Ian suggests and then store.

I have a lot of iron molds and when a casting session is over, I ALWAYS oil or grease the molds while they are still very warm. On brass or aluminum molds all the steel parts get oiled while hot. It is a routine, and it has served me well. By applying the oil while the mold is still hot, there is no possible way for any water vapor to have condensed on the material and the metal accepts the oil better. This requires the mold be degreased before each use but that’s the price you pay to keep rust away. :)

As for keeping a maintenance database for the mold itself – You’re a better man than I, Gunga Din !
 

hporter

Active Member
P&P, I appreciate the additional advice.

To be honest, I never thought about oiling down brass molds. Now it makes sense of course, with the corrosion I have seen on the sprue plates.

I do normally oil my steel molds thoroughly before putting them away. For some reason, the last time I used my 400 gr Snover mold for my 40-65, I didn't oil it and it was still in pristine condition. It literally looked brand new and unused.

It really puzzled me when doing this inventory exercise why 80 to 90 of my molds had no corrosion at all, and then others had minor surface rust on the top plate. They are stored in the same place, in the same airtight plastic containers. I don't know if in the end it will help, but I did add the food grade desiccant packs this time to every container. And I think I will switch to 2-cycle oil as Ian suggested rather than the 30 weight oil I had been using. Some of the iron molds, although there was no damage, were getting a bit sludgy with the 30 weight over time.

The maintenance database started when I couldn't find my .54 Rapine Sharps X-mas tree mold. I found my Moose Molds .54 X-mas tree, and my Tennessee .54 X-mas tree, so it drove me crazy and I became determined to document what I had on hand. I found the photo's of that Rapine mold and the Rapine .577 Minie Ball mold that came with it from an eBay purchase many years ago. I did find the .577 mold - so I know I am not crazy, but I still did not find the Rapine .54 X-mas tree mold. Goodness knows where it is at.

I have been having fun putting paper cartridges together for my 1859 Sharps carbine replica, and actually found a .54 caliber lee REAL mold and a .54 caliber Lee hollow base Minie mold that I had forgotten about. Of course all those different bullets need different cartridge lengths and mandrel sizes for rolling them. So that just adds to the fun. I was pleased yesterday when the el-cheapo metric wad punches I bought on Amazon chucked up in my drill press. Trying to punch out the Durofelt hard felt wads "whack a mole" style is tiring with the cheap tools I bought to do it. And the tip I read on the internet turned out to be true, a 13mm punched wad fits perfectly in the .54 sharps paper cartridges. Best of all, I found out my homemade SPG type lube when subjected to 10 hours of Houston 95 degree sunshine (and then a little rain) did not run out of the grooves of my x-mas tree bullet. I got tired of dip lubing them and tried running them through my Star. Much easier and cleaner - so long as there is enough lube in the grooves for that short carbine barrel.

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And I found a bunch of NOE and Accurate Molds 30 caliber rifle molds that I had forgotten I had purchased years ago. That was a further benefit of document everything. Then I also realized for insurance purposes, it would be good idea to take photos and document them all. I have already done that for my firearms. It made sense to do it for the molds too.

I have been enjoying shooting a variety of 30 caliber cast bullets out of my 300 blackout RAR bolt gun with small charges of Titegroup. I was happy that I found the additional molds to play with. Who knew that grown men cold have so much fun shooting steel plates with mouse fart loads at subsonic velocities. But my shooting buddy is now keeping an eye out for a 300 bolt gun..... We both got rid of our 300 Blackout AR uppers years ago. But the bolt guns are fun!
 

Bret4207

At the casting bench in the sky. RIP Bret.
I have moulds that seem more prone to rust than others. I don't know why.
 
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