Seasoning a Brass Mold

[Mal Paso]

By the time my 3rd Brass Mold arrived I knew the finish needed an oxide layer to resist Bullet Alloy from soldering to the brass but was unsure how to proceed. After cleaning the new mold I heat cycled it to 400F 3 times, blocks closed, in a gas oven. It cast Great but I started to get tinning at the hot spots and by 6,000 was getting little tearouts of the bands at the block faces where Alloy was stuck.

Meanwhile I had cleaned and did a chemical Patina on a MP 432256. I casts great but the process took all day and the finish wasn't even. I emailed Miha and he suggested Just Heat.

Today I cleaned the 432640 blocks with Chemtool, Dawn, and pure water. I don't know yet if this step is important but I used the formula Jailer posted: http://brewingrabble.com/resources/surface-lead.htm . It turned the mold a buttery yellow and hopefully removed lead traces (and maybe some zinc?). After a rinse I put the halves on the steel plate I formerly used for mold heating, Cavities Face Up, to get more Oxygen and set the burner a little less than I used preheating. I wanted the same heat but I had twice the contact area. (Remove Setscrew) The pictures are from an hour ago. The mold is already darker than my Liver of Sulfur treatment. I figure about 4 hours total. Guessing 400F.

The information I found on chemical patinas said brass was difficult. Jailer's formula may expose more copper which is easy to patina. I obviously need more molds to continue the experiment.

The mold is darker than it looks, the steel is pretty dark. Pic to show flame size.

[Dale53]

Mal;
I don't mean to minimize your problems. However, I have several Mihec (MP Molds) and have never done anything but pre-heat them on my hotplate (a steel surface burner, not Calrod) at about "medium". I want the moulds "just under" casting temp so I can bring them up to final heat with a couple of casts. My moulds cast beautifully (I have moulds for both solid only and hollow points). I have not had a problem with soldering of the bullet to the mould.

As a point of interest, I was told by a steel mould maker to hold a corner of a large block single cavity custom STEEL mould in the melt for five minutes to pre-heat the mould. I'll never do that again. The bullet soldered (in places) to the mould. To remove the bullet metal I had to gently heat it with a torch and wipe off. Luckily, it came off with a little effort.

I suggest you have just overheated the mould before casting. Just try not over heating when pre-heating and you'll be "good to go".

Good luck in the future.
Dale53

[cbrick]

I agree with Dale, I've never done any of those things to my brass molds, never needed to.

I pre-heat it just as dale does to a bit below casting temp, a bit of Bull Plate on the sprue plate once hot and start casting. My Miha molds are works of art and I've had zero problems, no patina, no jumping through hoops, pre-heat & cast. I'm really confused on what your trying to do or what you think it is you need to do.

Rick

[Mal Paso]

I preheat to just under casting temp and use the first couple casts finish bringing it up. Alloy 680F sometimes 690F to start My problem developed during the casting session. The tips of the bands adjacent to the block face don't dissipate heat as well and tin. John of Glencoe posted pix of his. My experiments showed an oxide layer prevented this. I'm sure in time all brass molds cure themselves with age but I want no stick now.

[mrbill2]

I have one brass mold from Accurate that I have never done anything but cast bullets with. No preheat or anything. The second time I cast I noticed the bullets were getting larger. When held to the light I could see light between the two halves. I check to see if I could see anything holding the halves apart but found nothing. Checked on a surface plate and found the halves are warped.
Found this warning about brass molds on Accurate's site after the damage was done. How lucky can I get.

Brass molds can warp if overheated. This will not happen with normal casting temperatures, where the mold block typically reaches about 325 degrees. If you preheat your molds, be careful not to get brass too hot. Brass makes a great mold block, but cannot be abused. I do not guarantee against warpage.

Just My 2 cents.

[Mal Paso]

I cast 15 lbs of 432460s with the heat treated mold last night and it was the best session I've had. Lead doesn't stick. There was a little in the minute gaps around the pins but nothing above that.

Cleaning stuck Alloy off bright brass is difficult and dangerous for the mold. Miha's molds are works of art and I want to keep cleaning to a minimum. Guys have said "Just heat it up and wipe the lead off with a rag." That won't work with bright brass, it smears.

My current recommendation is to thuroughly clean the mold then heat it with blocks open to 400F for 4 hours before the first cast. YMMV but a smooth even brown is the goal. The inside corners next to the bands will be the last to turn. Electric oven or hotplate, in a gas oven Oxygen is reduced so less effective. The "brewers" cleaning solution may help but I have not done side by side tests. It didn't hurt anything. Mold still casts .433 with minimal seam lines.

I think the oxide slows heat transfer from the Alloy. I've had to set the PID controller up 10* to 690F for prefect fillout and in mold time is longer producing about 11 boolits a minute.

It may be that my molds get a lot of use. The MP 432256 has cast a half ton of lead. Anything left out? My Alloy is about 3% Antimony, less than 2% Tin. I cast facing South.:grin:

[quasi]

half a ton, you really cast a lot!

[Baryngyl]

Anything left out?
Sitting or standing?
Do you hold your breath as you open the sprue plate?
Did you sacrifice a virgin at sunup while chanting a spell?




:kidding:

Michael Grace

[Mal Paso]

Sitting or standing?
Do you hold your breath as you open the sprue plate?
Did you sacrifice a virgin at sunup while chanting a spell?


Everything except the virgin. They are too few and far between.[smilie=l:

The devil is in the details. There are so many things we do automatically and don't think to include that make a huge difference. And things we leave out so they won't confuse the subject. And stuff we haven't thought of yet like:

My molds were stored in a warm dry heated environment. Others may have high humidity that solved their problem.

If I remember correctly, the reason Tom only offered only 3 cavity brass for a long time was the quality of brass available in this country. Sounds like he solved the problem.

I think all metal has some "grain" and the best machinists use it to their advantage like a carpenter puts crown up. Can't say that's the reason but all 3 of my MP molds are like .0005 concave to the mold face so the alignment pins always have perfect fit. The gap is way too small to cause finning and any difference between cavities is so small I haven't noticed.

If any Mold Makers have input, please have at it.

[Mal Paso]

half a ton, you really cast a lot!

To be fair I only seriously practice with 44 and until the 432640 arrived the 432256 was the only mold I cast regularly. I am also well past 100 pounds of 2400.

It all started with Bear that led to a 44 and the discovery that I was a poor pistol shot and if I was going to be more than a liability, I had to work at it.

[JonB_in_Glencoe]

I took a photo journal, figuring I was onto an easy way
to get a nice patina on a new brass mold. BUT I had problems :cry:
So I desided I wasn't going to post this as its kind of embarassing:violin:
although not a major failure, surely not a success.
But since my name was brought up for my photo of
the "soldering" on my first AM mold.
previously posted in this thread.
http://castboolits.gunloads.com/showthread.php?169575-Brass-Patina-Recipe
It's a AM 41 WC which I probably cast about 1000 boolits with it
during 3 sessions to result in this.
http://i640.photobucket.com/albums/uu127/JonB_in_Glencoe/closeup-1.jpg

It took about 2 hours to remove the soldering from 4 of these 5
brass molds, one was never cast with. Since I am setup to use a
Hot Citric bath to clean rangebrass cases, After I removed the
"soldering" I thought The de-tarnish/passivate would be a great
next step using the Hot Citric bath. (as suggested by Gear as this
maybe enough of a barrier to inhibit future "soldering")

Well, I've never seen brass so clean !!!
Any thought of skipping the next step was blanked out by the
super clean brass. Photo was taken right after hot Citric Bath.
http://i640.photobucket.com/albums/uu127/JonB_in_Glencoe/brassmoldsafterleadremovalandhotcitricbath.jpg


As I asked in the old patina thread (above link), I desided to try
adding fresh Black Powder (2 TBLSP) and disolving it into 2 quarts
of hot water. I dunked the molds (yeah I tried this on all of them,
instead of smartly just trying one mold), then put them on a
hot wood stove...the surface was about 350º. They'd sizzle dry in
a minute. I let them get up to temp (350ish I guess). Then I repeated
the dunking, and heating, and dunking, and heating...about 4 times.
Then I rinsed them with clean tap water, and heated them, then rinsed again.
then I let them on the wood stove over night as the fire grew cold.
They looked pretty good, but my livingroom (where the wood stove is)
is kinda dark. I took the photo below the next morning with that same
lighting in the kitchen as the photo above, to give the best representation
of the patina/Season.

The problem was (I didn't notice this until it til I was taking this last photo)
that the citric acid bath removed all the bluing, except were the sprue
plate was above the water line or tight against the brass mold.
I got some flash rusting on all the now Non-blued steel parts, but mostly
on the allignment pins, but only on the MP molds, the AM pins must be stainless?
So I rubbed some Bull Plate oil on them with a q-tip, then rubbed them with
a course shop rag, and repeated that til they looked rust free. I'll be keeping
a close eye on them as they get used and then stored.

I haven't taken any time to cast with any of them yet, they open and close
the same as they did before. The patina/season is quite light in color but
it is fairly uniform. Some day soon when I get to cast with some of them,
I'll report back.


http://i640.photobucket.com/albums/uu127/JonB_in_Glencoe/brassmoldsafterBPsolutiondunkandheatcycles.jpg

[Iron Mike Golf]

Would a heat cycle or two "fire blue" the pins and sprue plate? Seems to do that with mine. Not sure if it was preheat for casting, though.

[quasi]

how about this stuff?

http://www.brownells.com/gunsmith-tools-supplies/metal-prep-coloring/blackening-browning/brass-black-prod24777.aspx

just my luck, they will not ship this to Kanaduh.

[huntrick64]

I have heat-cycled some of my MP brass molds and some I haven't. Don't really notice a difference either way. I have noticed that when I get into a really long casting session (like 3-4 hours for me) I do get some tinning in the same areas as the last photos, but not as severe. I simply keep a small (large marble size) ball of bronze wool handy and wipe it away right after I drop the bullets. It comes off really easy when the mold is casting hot and doesn't appear to smear around. Tried chore boy as well, but bronze wool works better for this.

I use it more often for removing the smeared lead from the bottom of the sprue plate that is caused when I get in too much of a hurry and cut the sprues before they have completely set up. Get you a ball of this stuff and keep it in your casting stuff. It is a handy tool.

[Mal Paso]

how about this stuff?

http://www.brownells.com/gunsmith-tools-supplies/metal-prep-coloring/blackening-browning/brass-black-prod24777.aspx

just my luck, they will not ship this to Kanaduh.

Too much chemistry. You may get undesirable side effects. All you need is an oxide layer.

My best luck was, after through cleaning, treat the mold with the brewers formula: http://brewingrabble.com/resources/surface-lead.htm Just like it says then heat the mold to operating temperature with cavities exposed for about 4 hours. This time you are looking for uniform brown.

Bronze wool is great! Brownells has it. Beeswax on a hot mold will help lift the lead.

Edit: Ever try to solder copper water pipe that has naturally over time turned brown? You can't! That is what I'm looking for. There are many commercial metal finishes but there may be side effects, you would have to test. I tried Liver of Sulfur, a jewelers go-to, which worked ok. I think the oxidation is impeded by the Surface lead and zinc Molecules in the brass. The mild vinegar / peroxide bath removes those protective molecules exposing copper which is easy to oxidize.

I cast 1500 Boolits yesterday and the couple times I cut the sprues early the lead wiped off with a Q-tip with sprue lube on it. I used to use bronze wool.

[dragon813gt]

The problem was (I didn't notice this until it til I was taking this last photo)
that the citric acid bath removed all the bluing, except were the sprue
plate was above the water line or tight against the brass mold.
I got some flash rusting on all the now Non-blued steel parts, but mostly
on the allignment pins, but only on the MP molds, the AM pins must be stainless?


I wouldn't worry to much. I live in a humid climate and mine have started to rust. I just keep them oiled and everything has been fine. I found out that Ruger's stainless barrels are of the type that rust. Living in the north east but in an area that has a humid continental to almost subtropical climate makes owning anything metal a pain.

I heat cycled all my MP molds last. night. Two of then were brand new. The new ones are now the same shade as my old ones. The old ones didn't change at all. It seems that heat cycling the new ones did the same thing as a few casting sessions would have. I was hoping to get a darker patina because I have sticking issues with them. The bullets very rarely just fall out.




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[40Super]

So far with all my brass molds, both Accurate and M-P, I heated and cooled 4 or 5 times before ever using. I leave them open when heating and just let them get up to casting temp for a couple minutes then turn the heat off to let cool, then repeat. So far non have done any soldering and the AM mold just rains perfect boolets. The M-P's tend to stick a bit and need the handle tapped to drop(quite often they are stuck on the pins) but no soldering, I just need to do a little lementing with comet and a boolit sometime.

[Shuz]

I've been following this thread with interest ever since I ordered an MP-433-300 in 4C for my Marlin 444. I rec'd the mould yesterday and lubed the pins and sprue plate with the lube Miha provides with his moulds. I then placed the mould on top of my old Lyman 20 pound pot and let the mould warm up as the alloy melted. When the alloy reached 700 deg, I started casting. The first few drops were a little imperfect with wrinkles, but then it settled in and cast beautifully. I had the same experience with my first MP mould, a 431-256. Any others I get will get the same procedure.

[Changeling]

I told this forum several years ago that the Hollow point pins needed to be heat treated in regard to MP molds (or any molds) to make them release reliably, however I was made out to be an idiot, so enjoy!

[Springfield]

I just cast with my 8 or 9 Mihec HP moulds, after a few bullets they all work fine. Just keep things hot. I didn't even clean the last 4, figure burning off the oil will season the mould just fine! Maybe I am just lazy but i try to not overthink this stuff, just want to cast bullets and go shoot.

[Old School Big Bore]

I have several MP molds; they're my first brass ones. When they were new, I scrubbed them with mineral spirit, then blasted them off with carb cleaner. Then I buffed MP lube into the steel surfaces, assembled everything and set them on a hotplate set on medium. As the alloy came to temp I flipped the molds over so both the pins and the sprue plates would heat up. The molds all like hot alloy, about 850•F. They all started out with about a 25% reject rate, but on about their third session the reject rate went down to practically nothing.