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Mushroom casting, some specific questions.

Discussion in 'Molding and Casting' started by kayanddodger, Nov 7, 2006.

  1. kayanddodger

    kayanddodger New Member

    Here is my predicament. I want porcelain mushrooms. To get this I need a plaster mold. This is where things get tricky.

    A little bit about mushrooms:

    Mushrooms, like humans, consist of mainly water. Fungus needs moisture in order to produce a fruiting body. Water makes mushrooms melt. seriously. the next time there's a big rain storm, look for mushrooms. If you manage to find a few, try touching them, you'll get my drift. Mushrooms are dried by scientist by being put in a heated and ventilated container. they are dried by normal people who want to eat them by being strung together and hung above a stove.

    Anyway, my worries are thus:

    1. the mushroom will absorb the water from the plaster and ruin the mold and lose it's shape.
    2. the water from the plaster will "melt" the mushroom
    3. the heat from the plaster will reduce my positive to a stew.
    4. the heat will make the mushroom dry up and lose shape.

    I don't think it's possible to make a plaster mold from a mushroom. I could coat it with tons of vaseline and pray that it's ok. But that's a long shot and it probably wouldn't work. I could cut the mushroom, very carefully, with an x-acto along the seam. but I think that the form is too fragile and it would be useless. My best bet is to make a rubber mold and then make a plastic cast and make a plaster mold from that. But I don't own any of the materials, and I really have some problems with using museum materials for personal projects. I could try layering latex on to the mushroom and using that as a positive for a quick plaster cast. I could use wax... but I don't know enough about wax molds...
  2. Susan

    Susan New Member

    Use alginate to cast your mushroom (in a cup). Stick a wire either through the stem or hook it in the base of the stem to suspend it in the cup while you pour in the alginate. Once the mix cures, gently "slice" the mold in half(at the most sensible angle for re-casting). The mold will feel slightly soggy to the touch, so be gentle with it. If it is allowed to completely dry it will warp and the mold won't fit together, so don't start this project until you're ready to see it all the way through.
    Gently clean out your mold with a soft bristle brush-using a tooth pick if needed to pry any solid parts out. The base of the mushroom being the "top" of your mold- spray release agent in the mold, tape it together carefully to line-up the casting edges, and pour polyeurathane foam to make a casting. I always try to make 5 or 6 castings before disposing of this alginate mold.
    Yep...these castings are rouge. After trimming the flashing edges off of it, take potters clay or epoxy and seal the surface of these castings. These "dressed" castings are then used to make my plaster molds. I fix 5-6 so that I can make the plaster mold to produce this many at one time.
    Hope this helps!- Susan

  3. Just face it. In order to get something you have to put out something. I think in this case, you need to put out money to get the right casting materials. I have had great luck with smooth-on rebound 25 on various forms of fungi. I form a dam around the mushroom while it's still planted in the ground. I mix the rubber and pour. I let the mold set and then bring it in the house. I let the mold set inside for a couple of days to let the mushroom break down for easier removal. Then I pick out as much of the mush as I can using various tools.
    I cast with plastic, so the first couple of casts pull the remaining material out of the mold. You can make many pulls from one mold this way.
  4. I agree with doug on this one. I have used similar methods to cast mushrooms and morel mushrooms with rtv in the same way with good success. then take the first pull and fix any slight problems such as air bubbles etc and remold with rtv again. You might get by6 with a plaster mold if you sealed it with lacquer like you do with fish but i am not sure. also i imagine using a fast setting plaster would help as well. all that being said I would go with rtv and recast off a plastic pull.