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Re: More alginate info

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  • Andrew Hart
    Thanks to everyone who offered advice on using alginate as a mold making material. I ll give it another shot at some point, but I ll probably only use it for
    Message 1 of 7 , Jan 6, 1999
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      Thanks to everyone who offered advice on using alginate as a mold making
      material. I'll give it another shot at some point, but I'll probably only
      use it for life-casting projects. I've still another can of the regular
      set alginate out in the garage. Incidentally, what mixing ratio (water to
      alginate) do you guys use?

      But for more pressing questions...

      As I might have said before, I'm more or less a complete novice at casting
      and sculpture. I sculpted one piece, decided I liked it, and made another
      figure with the intention from the start of making molds of the pieces and
      being able to reproduce it. I learned that making molds is at least as
      difficult as sculpting!

      I have (hastily) prepared some web pages of my project. It can be found at
      http://www.mind-logic.com/sculpture

      If any of you experts have the time to look it over and give me some
      pointers, I would be greatly appreciative. Gramps V2.0 is the project I
      need feedback on. If you go to the third page, you'll see that I'm
      preparing to make the mold for the body. This is my first attempt using a
      lego box as a mold box and my first attempt at using a clay wall for a two
      part mold. Previously, I've just managed to suspend the part and pour it
      in two halves. On page three, you'll find a picture of the lego box and
      clay wall. Tell me if you think it looks satisfactory.

      Also, some questions...

      Should I put RTV mold release agent on the clay wall? I've read that you
      shouldn't put it on the master. Should I put mold release on the inside of
      the lego blocks? As mention on the web page, I'm using micro-mark one to
      one RTV rubber and it REALLY stuck to a pyrex mixing bowl I was using. I
      would hate it if it stuck to my lego blocks. I know that over his chest,
      I'm going to have a big solid block of RTV rubber... not exactly cost
      efficient... but I want to make a durable mold. When I have poured the
      first part of the mold (which will end up being the bottom), then I'm going
      to have to dismantle the lego box and clean off all of the clay. What is
      the best way to do that? I've noticed that this stuff can be a bit messy
      once it's been stuck on a surface for a while. Hmmm, if you think of
      anything else, please elt me know. Again, the URL is:

      http://www.mind-logic.com/sculpture/


      Page three of the Gramps V2.0 project is the pertinent page. It's
      interesting to see that we have garage kit sculptors here on the list.
      I've never even built a garage kit before, so perhaps I'm getting the cart
      before the horse by trying to make one of my own. Let me know how you
      think it turned out.

      Thanks...


      --
      --- Andy
    • Steve Kann
      ... I m not an expert (just poured my first castings yesterday), but I used a clay wall, and put mold release on the clay as well as the master. That seemed to
      Message 2 of 7 , Jan 7, 1999
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        On Wed, Jan 06, 1999 at 04:30:21PM -0600, Andrew Hart wrote:
        > From: Andrew Hart <andy@...>
        >
        > Also, some questions...
        >
        > Should I put RTV mold release agent on the clay wall? I've read that you
        > shouldn't put it on the master. Should I put mold release on the inside of
        > the lego blocks? As mention on the web page, I'm using micro-mark one to

        I'm not an expert (just poured my first castings yesterday), but I used
        a clay wall, and put mold release on the clay as well as the master.
        That seemed to be no problem at all. (I tried the release on a
        non-critical part of the master first, to see if it caused any damage).

        > one RTV rubber and it REALLY stuck to a pyrex mixing bowl I was using. I
        > would hate it if it stuck to my lego blocks. I know that over his chest,
        > I'm going to have a big solid block of RTV rubber... not exactly cost
        > efficient... but I want to make a durable mold. When I have poured the
        > first part of the mold (which will end up being the bottom), then I'm going
        > to have to dismantle the lego box and clean off all of the clay. What is
        > the best way to do that?

        Cleaning the clay from a lego box shouldn't be too hard -- it will only
        be on the flat surfaces, and some residual clay on the lego box won't be
        a problem anyways.


        Here were my problems:

        I used clay to cover half of my pattern to make a two part mold. I
        had two problems with this:

        a) It's really hard to clean the clay off of areas you don't
        want it, expecially on detailed areas, etc. It also
        leaves some residue which affects the finish of the
        reproduced parts.
        b) I seem to have had some "seepage" around the master when
        pouring the second half of the mold. Maybe I wasn't careful enough when
        placing the master back in the first half of the mold after cleaning.
        It may also have been some flex, as I applied some pressure to the mold
        when building a clay wall. I'll use legos next time!

        I did molds of two subway car ends. (basically the same, one end is
        "blind", the other has some cutouts for signage, etc). I got things
        that resembled the cars, but not reallyu useful for modeling, unless I
        wanted to model what the car would look like if it sat around unattended
        to rot for about 20 years :)

        -SteveK


        --
        Steve Kann - Horizon Live Distance Learning - 841 Broadway, Suite 502
        Personal:stevek@... Business:stevek@... (212) 533-1775
        "The box said 'Requires Windows 95, NT, or better,' so I installed Linux."
      • Ed Diceman
        I used clay to cover half of my pattern to make a two part mold. I had two problems with this: a) It s really hard to clean the clay off of areas you don t
        Message 3 of 7 , Jan 7, 1999
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          I used clay to cover half of my pattern to make a two part mold. I
          had two problems with this:

          a) It's really hard to clean the clay off of areas you don't
          want it, expecially on detailed areas, etc. It also
          leaves some residue which affects the finish of the
          reproduced parts.

          First off...did you use a water based clay?It works best and is VERY
          easy to clean off,just a toothbrush and some warm water will do!


          b) I seem to have had some "seepage" around the master when
          pouring the second half of the mold. Maybe I wasn't careful enough when
          placing the master back in the first half of the mold after cleaning.
          It may also have been some flex, as I applied some pressure to the mold
          when building a clay wall. I'll use legos next time!


          YOUCH!!NEVER remove the master from the mold.Remove the clay from it and
          DO NOT take the part out of the mold.This WILL cause seepage and if not
          corrected properly will cause defects in the catsings.I make box molds
          out of corrugated cardboard.it's easy cheap and effective,just remember
          to go "with" the grain of the cardboard!

          Ed
        • Mike Bauers
          Steve Kann wrote: ... Steve, If these are complete ends, and only ends...... look in the archives for some posts on what I termed block/gill molds. No clay
          Message 4 of 7 , Jan 7, 1999
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            Steve Kann wrote:
            ....
            > I did molds of two subway car ends. (basically the same, one end is
            > "blind", the other has some cutouts for signage, etc). I got things
            > that resembled the cars, but not reallyu useful for modeling, unless I
            > wanted to model what the car would look like if it sat around unattended
            > to rot for about 20 years :)

            Steve,

            If these are complete ends, and only ends...... look in the archives for
            some posts on what I termed 'block/gill' molds.

            No clay needed, one pour to make a two sided mold. You orient the master
            to stand vertical and pour the RTV around it. Slit the mold to remove
            the pattern and cast in that.

            Mike Bauers
          • Mike Bauers
            ... You re on the right track. It s the position of the master that makes it easy to remove. You glue the master to a base plate, wall around that and pour the
            Message 5 of 7 , Jan 7, 1999
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              Boone Morrison wrote:
              >
              > From: boone@... (Boone Morrison)
              >
              > >From: Mike Bauers <mwbauers@...>
              > >
              > >If these are complete ends, and only ends...... look in the archives for
              > >some posts on what I termed 'block/gill' molds.
              > >
              > >No clay needed, one pour to make a two sided mold. You orient the master
              > >to stand vertical and pour the RTV around it. Slit the mold to remove
              > >the pattern and cast in that.
              > >
              > >Mike Bauers
              >
              > Mike: This sounds like an interesting technique. I tried this once but
              > had great difficulty in orienting my cut. In my case it was a very small
              > part, but I still wonder if you have some technique for this. Hopefully,
              > there is a way to "find" the master inside so you can cut at a proper
              > parting line location.
              >
              > Or, am I asking too much here?

              You're on the right track. It's the position of the master that makes it
              easy to remove.

              You glue the master to a base plate, wall around that and pour the RTV,
              the next day you strip the rubber from the base plate and you master is
              right in front of you. Flush with that surface of the block of RTV.

              As you can guess, I like to use some sort of rubber like cement to
              attach the master to the base plate. It stays in the block when you peel
              the mold from the base. Since you can see where the master is, you just
              slice from the edge of the master to the edge of the block and then cut
              down the side of the block just far enough to flex open the mold and
              release the master. Your baseplate side becomes the working top of the
              mold.

              If you want more guides, lay some tiny strip plastic on the base plate
              that leads from the edge of the master and runs to the mold walls.
              You'll see those in the mold when you remove the cured block from the
              base and walls.

              Make certain you are making a mold that has extra rubber above the
              masters to use as a hinge. You can make a single block mold that has the
              sides and ends of a railcar and has to be fanned to remove castings.

              Line them in a string or side by side to mold.

              Think 'fan' or 'gill' as an operating design for this sort of mold.

              Window openings need to be covered with a single layer of scotch tape
              and then sealed with a layer of thin paint. That way you can make a
              block mold in one pour one even a multiple windowed RR car side. Just
              paint both sides of a master to seal the added tape. There is a trick to
              make this an easy punch-out. Place a piece of waste in the center of the
              taped opening before you seal the master. This just punches out,
              connected by a very thin film of the cast tape.

              Expect to have to install overflow vents to the tops of your masters to
              have the metal or plastic fill the mold completely. You can attach a
              thin strip of plastic to the top of your master, glue a thicker strip to
              the very top of that, away from the master. Then when you cast in the
              mold, you'll have a easily removed strip of waste that allowed the
              important part of your master to completely cast.

              I think that covers it?

              Mike Bauers
            • boone@xxxxx.xxxxxxxxxxxxxxxxxxx)
              ... Mike: This sounds like an interesting technique. I tried this once but had great difficulty in orienting my cut. In my case it was a very small part,
              Message 6 of 7 , Jan 7, 1999
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                >From: Mike Bauers <mwbauers@...>
                >
                >If these are complete ends, and only ends...... look in the archives for
                >some posts on what I termed 'block/gill' molds.
                >
                >No clay needed, one pour to make a two sided mold. You orient the master
                >to stand vertical and pour the RTV around it. Slit the mold to remove
                >the pattern and cast in that.
                >
                >Mike Bauers


                Mike: This sounds like an interesting technique. I tried this once but
                had great difficulty in orienting my cut. In my case it was a very small
                part, but I still wonder if you have some technique for this. Hopefully,
                there is a way to "find" the master inside so you can cut at a proper
                parting line location.

                Or, am I asking too much here?

                Aloha, Boone
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