Brass Mold - Prepping, Cleaning, Lead Removal, Patina & Smoking

[GMT210]

I have several Mihec molds and started off just cleaning with hot water and dawn, and smoking them a little bit. I've been reading several of the posts about patina and lead removal and decided to check my molds with a magnifier and discovered that I also have some of the fine tinning "oxidation" and started to search for cleaning methods. I found several different posts and opinions and decided to summarize them and see if we could get a concensus on what is best before I attempt to clean up my molds and prep a couple of new ones. Here's what I've found as the generally accepted methods.

Prepping a New Mold – Clean with hot water and dawn, dry (warm up) and then heat cycle.

Heat Cycling – Remove all steel hardware except for alignment pins, heat in oven at 400° with blocks separated for 15-30 min; allow to cool to room temperature, repeat 3-4 times.

Lead Removal – Clean mold with hot water and dawn, bring mold up to casting temperature 400°, apply small amount of beeswax rub with sharpened popsicle stick, toothpick, bamboo skewer or sharpened pencil to remove lead a cleaning patch can be used to wipe the lead off.

Acetic Acid/Hydrogen Peroxide – 2:1 volume of Acetic Acid to Hydrogen Peroxide, 5% Acetic Acid (White Distilled Vinegar) and 3% Hydrogen Peroxide. The process was expected to take longer with the more dilute solution, so the brass part was immersed for 10 minutes. The results showed the same gold
color and the Lead Test swab indicated the lead had been removed. The buttery yellow gold color can be used as an indicator that the process has completed. Home Lead Test kits should be available at most hardware stores.

This procedure for removing surface lead from brass can easily be conducted at home. A 10-15 minute dunk, swirl, and rinse in a 2/1 volume ratio of 5% Acetic Acid and 3% Hydrogen Peroxide has been shown to be effective. By the way, the solution can be irritating to the skin so either wear gloves or use
tongs.

Smoking a mold – Use a propane/butane lighter not a candle, the candle wax leaves a greasy smoke. Works, but is generally considered a cover-up for other problems or until the mold naturally oxidizes.


Why brass molds get tin oxidation – “from Geargasher & Springfield” it isn't lead, or tin, that's why it won't melt away. It is accumulated oxides of mostly tin, it starts a 'seed' in a shiny spot and just builds and builds a few molecules at a time from the flash-oxidized molten surface of the metal you pour into the cavities. It's the same sort of stubborn crud that clings to the sides of a casting furnace as the alloy level drops. A reducant like beeswax or paraffin quickly takes care of it once you get the mould up to the melt point of the elemental metal.

Being an oxide, and beeswax being a reducant as JonBinGlencoe pointed out above, you can heat the mould to the point that the tin would start to melt if it weren't oxidized, apply the wax to instantly reduce the oxides to elemental, liquid metal, and wipe them away.

It happens to me with brass moulds because they do like to be run hot, it IS worse with binary lead/tin alloys, and the brass moulds DO like to be run hotter/faster than other types which DOES exacerbate the oxide accumulation.

What I do to patina a brass mould for the first session is preheat it to casting temp in a mould oven and let it cool naturally a few times, then smoke the cavities lightly with a BBQ grill lighter before ever putting lead in there. That keeps those little soldered "seeds" from ever starting. After a few casting sessions, I wipe out the soot and leave them alone. This is the only time I ever smoke moulds because it can cause a lot of other problems, but it really helps break-in with brass.

What are your thoughts?

GMT

[GMT210]

After over a 110 views, nobody has any thoughts?

[jbelder]

I don't think you need to pull it apart. Just clean it, heat cycle and cast away.

[dragon813gt]

I didn't bother reading past the first two parts because I don't agree with either. My molds have never had water close to them. Miha does a good job of removing most of the cutting oils. To clean them all it takes is a few shots of carb cleaner and towel dry.

There is no need to take the molds apart when heat cycling. In fact it's the opposite of what you want to do. Keep everything together an make sure you have the pins inserted as well. You do want to keep the mold halves separated. Cycle three or four times like this and when you're done everything will be set in.

After the heat cycling is when I pull them apart to properly lube everything. I don't know what everyone is doing wrong. I've been able to remove any tinning with a toothpick. Make sure you heat cycle before pouring lead into them. This starts the patina building. Just casting with it keeps the process going.

[cbrick]

I didn't agree with most of it either. With a thorough search you could probably learn that your boolits will never turn out "right" unless you cast while standing on your head eating bugs.

I clean all new molds with denatured alcohol and an old tooth brush. Water never gets near any of my molds.

I have never heat cycled a mold & never saw any particular need to do so. Molds I have had for decades and my newest molds from Miha seem to function perfectly without this step & never saw a need to start. I have read on this forum that aluminum molds need this process to help seat permanently the guide pins, possible I suppose but I have never had an issue with loose guide pins.

Soak a mold in vinegar to remove lead? Could work I guess but I have never had lead on mold that couldn't be removed by simply rubbing a hot mold with a dry Q-tip and/or a wood stick.

Smoking molds is an old wives tale that at best, if it does anything except gunk up a mold that you just spent time getting clean is cover up a problem. I've always found it best to keep the mold clean and find & correct the problem.

I've never had a problem with oxidized tin in my molds or clinging to the sides of my pot as the level of alloy drops. My current casting pot has never had any flux in it except sawdust and as the level drops the sides look nearly as it did when new, nothing clinging to it. I also never use a wood stick to stir the pot as many here do & claim it is a dream come true. I do add 2% pure tin to all of my alloy but I can't see where it is building up on my molds or my pot.

For those that use these steps and feel they help get better boolits then they are absolutely doing things correctly for them. As for me, I can't seem to convince myself that bugs would be very tasty. I am very pleased with the way my boolits turn out and my molds seem to work quite well without standing on my head.

Rick

[GMT210]

Cbrick & Dragon813gt,

Thanks for the response, that is exactly why I summarized all the different posts and was asking who does what and to get a conversation going about it.

GMT

[quasi]

I have quit heat cycling my MP and NOE new moulds as well, I have seen no difference in casting speed or quality. In my experience , the only thing that breaks in a mould is casting with it, be it Iron, Brass or Aluminum.

[btroj]

I scrub new moulds with hot water and comet. Rinse well, dry, and go cast.

I get mould to temp, lube pins and sprue plate, then make a bunch of bullets.

[DanM]

I have heard that Comet or other ammoniated cleansers are tough on aluminum molds. Don't know about brass or iron. I use a milder cleanser like BonAmi, Bar Keepers Friend, or Zud. Those contain no ammonia or abrasives at all and still do the job fine....DanM

[Iron Mike Golf]

DanM, keep in mind that Bar Keeper's Friend has oxalic acid in it. It'll take the blue off a steel or iron mold and screws right quick. I wouldn't leave it on very long. Left a stainless teaspoon in the bowl for a few hours and it etched the spoon nicely. Mrs was not amused.

[longbow]

My mould prep for new moulds (brass in particular) consists of:

- opening the package and admiring the shiny new mould
- putting any pins or bits together
- checking for any burrs, especially on the sprue plate
- checking the sprue plate tightness and set if required (it should almost swing on its own in my opinion)
- put handles on it
- lubricate pins and sprue plate
- checking the cavities for any oil or sprue plate lube I might have gotten into them and if so wiping with a rag or paper towel
- pre-heat until the sprue plate lube smokes a bit then cast with hot alloy

I do not heat cycle, I have never had "patina" problems resulting in lead or tin or tin oxides sticking, I do not scrub with Dawn and do not wash down with brake cleaner, solvent or whatever. I did use brake cleaner on my first Mihec brass mould because fillout was a little iffy when I started casting and I figured maybe I finally got one with "oil in the pores" but it was just as iffy after so I ran a little hotter and problem solved.

Used mould prep consists of:

- wiping the oil off the mould with a rag or paper towel (I oil all my moulds for storage including brass and aluminum because the steel bits can still rust ~ never had a mould rust after doing this so I know it works), then admire my old mould for a bit (I like moulds)
- probably add some sprue plate lube
- pre-heat until the sprue plate lube and/or remaining oil smokes
- cast

A good pre-heat has solved any fillout problem I have ever had except where there is bad venting which of course needs to be corrected. Sometimes just loosening the sprue plate will do it and sometimes (usually) I break the sharp edge at the mating faces under the sprue plate.

Never, ever had a problem or bad fillout doing this and never had a mould, sprue plate or pins rust doing this but different strokes for different folks.

Have at 'er in whatever way turns your crank. I am lazy though so do not bother with anything I find unnecessary.

Longbow

[btroj]

I haven't had any issues with comet thus far, been using it for almost 20 years on Al moulds. I suppose I need to wait and see?

[JonB_in_Glencoe]

After over a 110 views, nobody has any thoughts?
I just seen this post today.

Nearly everyone who posted in this thread obviously doesn't have an issue with 'tinning' on their brass mold/s. And to them I say, whatever they are doing, it must be working good. Brass molds like to be run hot, the hotter you run them, the more likely they'll develop tinned spots, especially near the points of a lube groove...lack of Heat dissipating is the likely suspect. Of the 6 brass molds I've owned, two of them 'tinned'. I've found putting a patina on the mold has seemingly eliminated my problem. I have only tried a convoluted recipe using hot water with Black powder dissolved in it. I am quite sure heating cycling a well cleaned mold would do an adequate job of 'patina-ing' a brass mold.

[sprinkintime]

I didn't bother reading past the first two parts because I don't agree with either. My molds have never had water close to them. Miha does a good job of removing most of the cutting oils. To clean them all it takes is a few shots of carb cleaner and towel dry.

There is no need to take the molds apart when heat cycling. In fact it's the opposite of what you want to do. Keep everything together an make sure you have the pins inserted as well. You do want to keep the mold halves separated. Cycle three or four times like this and when you're done everything will be set in.

After the heat cycling is when I pull them apart to properly lube everything. I don't know what everyone is doing wrong. I've been able to remove any tinning with a toothpick. Make sure you heat cycle before pouring lead into them. This starts the patina building. Just casting with it keeps the process going.

That's a +1, except use brake cleaner, does not leave a residue like carb cleaner

[dragon813gt]

The 2+2 I use leaves no residue behind. I know some of them tend to.

[Mal Paso]

I've never had fillout problems that were not temperature related. I've put sprue plate lube and beeswax in the cavities just to see and no effect. Not saying it doesn't happen, just not to me.

I find keeping a brass mold clean is much easier if the brass is oxidized. I clean the mold of oils that would inhibit oxidation and repel water. I next use the (water based) Vinegar/Peroxide solution to remove microscopic lead and zinc on the surface of the brass that impede oxidation of the Copper. I then heat treat to accelerate natural oxidation and maybe set the pins etc.

With a "Patina" the flecks of lead don't stick very well to the block faces and lead smears on top wipe off with a Q-tip and Sprue Plate Lube (Mold Hot).

This is what I do. Many have no problems and I am not the expert on brass molds although that's all I'm using now.

Last casting session I got down to a PID controlled 640F, Lee 4-20, and 3 1/2+ casts a minute. Good sharp edges no voids. MP 432256 260g #503 clone

[DanM]

Did not know that about BKF. Never had any issues with the can I used up. Have already changed over to BonAmi months ago just due to availability. Seems fine. Perhaps this is a non-issue since any cleanser never sits on the mold more than a couple of minutes during the cleaning process.

[Loudy13]

I was having just a heck of a time with my first Brass mold probably due to a little inexperience, running the lead to cold and so on. I have a NOE 311414 4 and I had quite a few spots of "tinning" and the points of the bullet had patina'ed so I was getting whiskers on all 4 bullets. I worked the hot molds with beeswax and removed most of the large spots of lead that had stuck to the mold but wasn't happy with the multiple small spots that would budge. I was also getting quite a bit of build up around the base of the mold which was distorting the bullet base.

I used the method below, first disassembling the mold and mixed the solution. I let the mold halves sit in the solution for about 10 minutes and then scrubbed with a toothbrush. I then cleaned the molds with hot water and dish detergent put the molds back together and placed on the warming plate. After dumping the bullets 3 times it was throwing perfect bullets once again. I still have small whiskers on the bullets but it is working much better. I did have about 2500 bullets cast up to this point so taking a little time and cleaning is well worth it if I can get that many castings before having to do maintenance.

Thanks CB once again for all the great info!!

Acetic Acid/Hydrogen Peroxide – 2:1 volume of Acetic Acid to Hydrogen Peroxide, 5% Acetic Acid (White Distilled Vinegar) and 3% Hydrogen Peroxide. The process was expected to take longer with the more dilute solution, so the brass part was immersed for 10 minutes. The results showed the same gold
color and the Lead Test swab indicated the lead had been removed. The buttery yellow gold color can be used as an indicator that the process has completed. Home Lead Test kits should be available at most hardware stores.

[Turbotrix]

253159
I know this is an old topic but I just got my first brass mould made by MP. This is what I used to clean the mould before use..IOSSO Case Cleaner it's pretty amazing for removing powder fouling carbon discoloration and oxidation.... it's used to soak cases or to use with ultrasonic cleaner but I had great results also adding just a bit of it into to my wet tumbling solution... I only heat cycled the mould once after reading this thread... I will keep everyone posted time progresses and I mold will need cleaning

[GONRA]

After all this "brass mould trouble - why not "Learn a lesson" and use TRADITIONAL CAST IRON moulds?
(Bet there's a Great Answer to this - WAAAAY over GONRA's paygrade!)
Over nearly 60 years, GONRA's cast a ZILLION boolits from cast iron moulds with little if any problems.
Without knowing ANYTHING about this BRASS MOULD STUFF, would assume BRASS moulds would TIN and generally Mess Up? ???

[Chill Wills]

?????????????

What is wrong with brass molds?
Nothing. Other than don't bang them around.
NO trouble. No break in.
Just great bullets.

[JimB..]

I purchased a brass mold here on the forum, it came in all tinned up. Heat and beeswax did little, was able to pick some out with a bamboo skewer. It’s been stuck in the back corner of a shelf for over a year now. Might try the ultrasonic cleaner next time I’m running it.

[John Boy]

Cast with Meehanite iron - brass and Aluminum with over 200 molds in inventory ... and all prepped the same way:
* Clean with a 5% solution of Micro-90, hot water rinse & wipe dry ... https://www.ipcol.com/cleaners/micro-90
* Heat mold on gas stove burner up to same temperature of fluxed melt
.... Start casting

[Loudy13]

After all this "brass mould trouble - why not "Learn a lesson" and use TRADITIONAL CAST IRON moulds?
(Bet there's a Great Answer to this - WAAAAY over GONRA's paygrade!)
Over nearly 60 years, GONRA's cast a ZILLION boolits from cast iron moulds with little if any problems.
Without knowing ANYTHING about this BRASS MOULD STUFF, would assume BRASS moulds would TIN and generally Mess Up? ???

Ha, well a few reasons, Hollow points! availability! Custom or unique molds! 4-6-8 cavities! reproduction of some of the great Molds (HG68!)
Steel moulds along with aluminum and Brass all have there issues..... I'm gonna "Learn a lesson" and produce tons of bullets with all types of mould materials just less with Iron molds