Cleaning Carbon Steel molds....

Discussion in 'Metal casting projects' started by Haus, Sep 4, 2021.

  1. Haus

    Haus Copper

    Hello all,

    I've only recently gotten into this whole melting/casting thing. I've been focusing on doing Aluminum melts, and about to do my first brass and copper melts.

    I found using steel baking pans gave me some options for cool looking ingots. I saw this one and picked it up :

    It's been working like a charm. First couple pours "burned out" the non-stick coating and now skulls are coming out wonderful and clean.

    But yesterday I had an issue. It had left some carbon residue in the mold, and it annoyed me so I wiped it clean (user stainless steel spray cleaner and paper towel). The next set some had some little "scars" and imperfections, I looked in the pan and sure enough some bits of aluminum had stuck to the pan. Here's an example... Clean from the mold on the left, after I had a couple rounds of sanding (up to 2000 grit) and polishing in the middle... and one of the "scarred" ones fresh from the mold on the end.


    Now I have a pan with imperfections in 2 of the 6 molds. Tried using a blowtorch to see if I could heat the aluminum enough to melt it out to no avail. Debating trying to sand it out, but then worried I will leave the surface so roughed up everything will refuse to pop out.


    Also is there a support group for people who just keep looking for novelty baking pans to make ingots? Asking for a friend.
  2. Petee716

    Petee716 Gold Banner Member

    The aluminum might be eating into the surface. FYI bronze (and probably brass, I don’t know) will stick in molds like those and you will end up peeling the steel off with pliers.


    PS burning Teflon is nasty nasty business.
  3. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Aluminum will actually dissolve steel. Your initial pours created and oxide layer that protected the steel and when you cleaned it, you removed that protective layer. Boron Nitride coatings are the professional solution. They can be purchased in spray can but expensive ~$50. Wipe it down with some light oil like WD-40 and heat your mold over your furnace until it turns brown/black. Leave that oxide layer and try some more aluminum casting.

    Petee is right about burning Teflon coatings. Very nasty. Stay far away from that initial firing of the coating.

  4. Tobho Mott

    Tobho Mott Gold Banner Member

    Molten metal is hard on baking pans... Does the underside of the pan have good enough detail for you? If so you could flip the pan upside down and ram up a sand mold of its underside to pour into. Another thing you could try is casting some plaster skull-muffuns in your pan to use as sand casting patterns. Good luck!

  5. FishbonzWV

    FishbonzWV Silver

    I'm going to go a completely different route here.
    Now that you've had fun learning what can be done, it's time to use your brain and see what you can create.
    That's what casting is all about, being able to make what you envision. :)
    Tobho Mott likes this.
  6. Haus

    Haus Copper

    Well, the point of the Skull muffins has been that they've given me interesting starting points to learn a few things. I'm all of around a month into learning this.
    1. Polishing/finishing techniques. (like the middle skull) Still working on this, figuring out the difference between rogue, green, white, brown polish sticks and a wheel polisher...
    2. And I plan on using some of the "pristine" ones for sandcasting. (just bought some petrosand after my initial greensand experiment turned out dicey..) Right now thinking of putting adhesive foam letters/numbers on them across the forehead, then sandcasting that for instance.
    3. If I get it down I might also make a basket of them for an artist friend to sell at her pop-up shop with a couple skull related holidays coming up. (If this hobby can eventually fund itself I'd be in heaven. heh)
    4. Have been tinkering with how to attach the right hardware to the back to make one a belt buckle. (Have not taught myself welding yet, so not quite to that level, thinking tapping screw holes and attaching that way)
    I had heard about aluminum eating at steel and figured that might be it (why people consider steel crucibles "very disposable"). Went back by the Joanns fabrics I got the original pan at and they were already on sale so picked up another for $6.50. Thanks for the tip on Boron Nitride, might give that a go. Found a "high temp" mold release spray including that on Amazon for $20 a can. ( )

    As for burning off the teflon, Thanks to doing a lot of DIY painting with a spray gun I have respirator I've been leveraging already. Also figure that will come in handy if/when I get around to things like brass that have a zinc component and risk generating zinc gasses.
  7. Haus

    Haus Copper

    As an example of #2 above today I did my first sandcasting. Took one of the polished ones, applied some adhesive foam numbers to make this... then stamped the year in. It's a gift for a friend for whom the number 141 has a lot of significance this year....
    Going for a slightly artistic "voodoo" vibe...
    BattyZ and Petee716 like this.
  8. Haus

    Haus Copper

    A little wrap up update on this one...

    I sanded down the inside of the molds where the aluminum had stuck to the steel. Then decided to test this stuff I saw on Amazon..:
    Gave the pan 2 coats of it, let it dry 20 minutes, and poured. Everything popped right out easy peasy.
    OCJohn likes this.
  9. Rohitstad

    Rohitstad Lead

    Hi! Are you sure that using baking pans is generally a good idea? Maybe it's better to use special forms?
  10. Haus

    Haus Copper

    Oh, I'd suspect there are far better overall forms to use. First off, these baking pans are good for Aluminum, but try copper, bronze, or brass and you'll probably get the metal fusing to the steel and not releasing. (even with the slide spray). I've had to toss my original skull pan after attempting a brass pour to make brass skulls.

    OTOH, for making quick 'aluminum muffins', these are cheap (under $10 for a pan, and I now also have heart shapes for Valentine's day, eggs/bunnies for Easter, etc...). Now, if I want one of them cast in a higher temp metal I just cast one in aluminum, sand it real nice, and use it for sand casting one in brass, bronze, etc...

    In the long term I am now looking at getting a CnC so I can mill my own graphite molds. That would be, by my estimation, to best I will be able to pull off with my DIY/hobbyist tier shop and budget.
  11. Rohitstad

    Rohitstad Lead

    As for cleaning, I think you need to use some very strong chemical cleaners for this. I recently addressed the guys with https://the drain cleaning, and they cleaned up a very complicated sewer blockage with some liquid agent. I think this cleaning agent is what you need. I suppose you can ask them what it was and try to use something like that. Good luck!

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