Home Forums General General Cold cast metal issue

This topic contains 5 replies, has 3 voices, and was last updated by  Mark Pearce 3 months, 1 week ago.

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  • #93081

    Mark Pearce
    Participant

    hi guys,

    I’m having a little issue with my cold cast metal, I’m coating the mould with brass powder, but 4 out of 5 times some of the powder has been displaced, leaving a small but noticeably dull area on the cast, which is infuriating when it’s otherwise perfect.

    I do pour from a reasonable height, maybe 5″ to prevent bubbles, though the powder doesn’t actually get displaced there, always just half an inch to the side.

    Any help on either how to repair (without amazing painting skills!) Or how to prevent/minimise the brass powder getting removed during the pour would be much appreciated!

    Thanks, Mark

    #93125
    Darkest Star Games
    Darkest Star Games
    Participant

    Alas, I have only tried this sort of thing once when trying to make a prop, and it did not go well for me.  I had the same sort of problem, though I was told that the remedy was to either used a “closed standard mold” and pressure chamber, or pour an open mold from closer and vibrate the mold to get rid of bubbles.  Thinking back to how the powder displaced as I poured, I wonder if perhaps the mold were slightly damp so the powder adhered better?

    "I saw this in a cartoon once, but I'm pretty sure I can do it..."

    #93135
    Mike
    Mike
    Keymaster

    Is this related to your previous topic about polishing a gazillion cast items?

    #93142

    Mark Pearce
    Participant

    It’s unrelated.

    I found a solution of my own, which may help other members in the future.

    After dusting your mould(rather than use a paint brush I find it better to pour some metal powder into the mould and rotate it and shake it around until it’s covered all over, tap the remainder out back into the bag), take your mould and spray a couple of light passes of a polyurethane spray. Wait 40 mins and then pour, the metal still adheres to the resin just fine, but the light coat of polyurethane spray aka clear acrylic stops the powder shifting as easily.

    Cheers,

    Mark.

    #93192
    Darkest Star Games
    Darkest Star Games
    Participant

    Very interesting tactic!  Did you use a gloss or matt spray?  I would be worried that a gloss spray might not allow the resin to adhere and leave either a brittle shell or somesuch.

    "I saw this in a cartoon once, but I'm pretty sure I can do it..."

    #93204

    Mark Pearce
    Participant

    It is actually gloss, very high gloss at that. Like you I suspect matt would make more sense but it’s what I had in. It comes up perfectly well with a fine wirewool and seems just as adhered to the resin as if the spray wasnt there. I’ve done it four times now, each perfectly successful 😀 hope it helps!

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