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Thread: Brass Mold Tinning (Again)

  1. #1
    Boolit Buddy
    DHDeal's Avatar
    Join Date
    Aug 2016
    South Carolina

    Brass Mold Tinning (Again)

    Over a period of a few months I've ended up with 6 MP brass molds, and like others have experienced over the years, got tinning on the mold faces. Part of the problem was obviously me as the molds cast so good I kept going and going to find the gunk in a few places after a long session. I wouldn't notice it until I looked at under a lighted magnifying glass. I've seen it on all of my brass molds to one degree or another. Every mold but one had been heat cycled multiple times before first use. One was thrown into the fight new to see if it makes any difference for me to go to the trouble of heat cycling. Hint: it does for me but the tinning is still a problem.

    As I'm casting I will keep an eye on the mold faces and wipe them either with my glove, or heavy duty bamboo Qtip (gun cleaning size) and this helps. I've even bought the Liquid Wrench dry lube and tried it (it helped somewhat and now use it on all my molds). However there is the tinning again after I look under the magnifying glass. I went through the tin seed removal process desribed many times on this site and can get it off, but wanted a better way if there is a such of a thing.

    I've also read where some have never had tinning with these molds for any number of reasons. I have and do have the issue, though it has lessened somewhat after many casting sessions. Someone mentioned liver of sulfur, someone else mentioned pencil lead, others mentioned whatever to coat the mold faces. I recently tried coating the faces with Brownells 44/40 cold bluing and gave it a go. So far it appears to work perfectly. Now with the mold faces being a light brown color, if I were to see any build up begin, I'd know it and wipe it off while the mold is hot. I don't find the tin removal to be a fun expenditure of time.

    These molds cast great looking bullets that just pile up quickly and are so easy to use. That said, I have many aluminum and iron molds that I just don't have the tinning issue with. Same alloys, same pot, same everything except the metal the mold is made from and temperature/cadence of casting due to the mold alloy.

    Has anybody else resorted to coating their brass molds recently?

  2. #2
    Boolit Master mattw's Avatar
    Join Date
    Oct 2014
    East Central Illinois
    Well, brass can be soldered to, aluminum and iron not so much with lead. I only have one brass mould and I have had some issues with it as well. I am not sure what starts it and I never get aggressive about removing it.

  3. #3

    ShooterAZ's Avatar
    Join Date
    Jan 2012
    Flagstaff, AZ
    I've noticed that the tinning is much more prevalent when the molds are relatively new. It will lessen after the mold gets a patina on it, just from use. Yeah, it's a pain...I use the sharp edge of a boolit base to scrape off the "seeds" while the mold is HOT. It happens, but your'e right...brass molds cast great looking boolits.

  4. #4
    Boolit Master

    RedHawk357Mag's Avatar
    Join Date
    Feb 2010
    Duncan, Oklahoma, United States
    Heat cycling is definitely a good step in preventing tinning. When you unbox these molds they are absolutely stunning. Stunning brass molds casting lead bullets leads to sad trombone. Heat cycling dulls the finish once you get that dull finish it will cast like gang busters. Removing tinning isn't a fantastic way to pass your day. Heat cycling is by far easier than removing tinning.

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  5. #5
    Boolit Bub Nodakjohns's Avatar
    Join Date
    Feb 2019
    I heat cycle mine when new. I have one that has a problem with tinning. Idk if i came with tue first or second casting session. But definately have to clean that mold up now. I jave only used it twice now and the second session i had to discontinue using it due to tinning. Hope it wears in. I have 5 bass molds.

  6. #6
    Boolit Master
    Dragonheart's Avatar
    Join Date
    Jan 2012
    Katy, Texas
    Use a Q-tip dipped in a 50/50 mix of hydrogen peroxide & white vinegar as it will remove lead deposits and give an almost instant patina. On stubborn lead spots dip a pencil eraser in the mix and rub. Then use the pencil lead to color the cavities, block faces and sprue plate to resist alloy sticking.

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check