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Casting Rocks from Latex Molds
Making Bragdon Rock Castings from Latex Molds
by Gary Myers

  1. Prep Rock Mold

    Clean out old debis in mold as best you can with fingers & vacuum. Use very,very light amount of vaseline (in top drawer of brown file cabinet under window), smear with fingers into every nook & cranny of mold, so that you have a barely, barely slimy mold. Use care to use only the lightest amount. Once you are done with this, you are done with the worst and most boring step.

  2. Outdoor Procedure (weather permitting, 65 deg < Ideal Temp < 85 deg)

    Take the mold outside (my sheet of cardboard for spraying is behind the tall file cabinet to the left of the window), spraying the white lacquer liberally (but not dripping), over the entire inside surface of the mold. I wore latex gloves so I could handle the mold to turn portions inside out to get it covered well in the nooks in tight places. Let dry (take a coffee break, but it takes usually less than 15 to 20 minutes).

  3. Prep Work Area

    Put down a few sheets of newspapers on the brown and yellow 3-drawer cabinets to make a good work area. This is necessary because you will need the newspapers to catch drips while working the mold and you will want to throw them away when finished.

  4. Mixing, Pouring & Spreading the Cast Satin (WEAR LATEX GLOVES)

    Pour equal portions of A + B into separate little cups. We filled the cups to the brim and barely had enough for a large mold. Slightly bigger cups would help. One person pour these two cups simultaneously into the bigger cup, which the other person stirs with a disposable spoon while the other person is pouring, stirring constantly for only 10 seconds. (COUNT!!) As soon as stirred, immediately pour the mixture over as much of the mold as possible. The two of you immediatley pick up the mold and get the fluid to roll into every nook & cranny by moving the mold up & down and around. After about 30-45 seconds or so, this will begin to set, and you both turn the mold upside facing the newspaper to get the cast satin to run down the "high points" of the mold, so you don't end up "holes" in your nooks and crannys. Some will drip onto the newspaper, if it seems like too much, wait a little and try again. If you need to make more cast satin to fill gaps, find a clean area to set the mold and mix a new batch (one batch should be all you need, but we filled the cups to the very brim and were messy to handle again, so you might be able to reuse if you are careful.) Let dry about 20-30 minutes, work on something else for awhile. The cast finish in the mold should feel dry & smooth to the touch when dry.

  5. Adding Yellow Foam Backing (WEAR LATEX GLOVES!!)

    Mix the dark foams A+B the same as above. pour immediately into mold and spread with a strip of cardboard, and spread quickly while the other person pours. We ended up needing to make another partial batch. Let all this sit for another 20-30 minutes, until the foam is no longer tacky.

  6. Removing the Casting from the Mold

    While the mold is still "hot", literally from curing (you will feel the heat while you are working it), hard to the touch but not sticky, start pealing the mold off the casting, working your way all the way around the edges while working towards the center of the mold. Do not be afraid to bend the casting while removing the mold, it is very flexible.

  7. Mounting the Casting

    Heat up the very hot hot glue gun (the pink one). The glue stays hot longer before it cools to give you more time. (It is super hot though, so use care.) Apply the mold to where you want it. While it is warm, it bends easily around anything you want to mount it to. If it cools too much and is too stiff, warm it up with the hot blow dryer in the brown file cabinet under the window. Err on the safe side to make sure you leave plenty of track clearance. We almost left the casting too close to the track until we remembered to look along the track and realized we needed to remove some blue foam to make sure everything would fit well and not possibly hit a train. We had to press fit the casting while the glue cooled, which we were able to do along different edges at different times, because the casting stays hot and flexible a lot longer than it takes for the hot glue to cool and hold.

  8. Filling the Gaps

    Use little pieces of rocks in the castings box to fill up areas between different castings.

  9. Beauty is in the Eye of the Beholder!

    You're done! Have another coffee and step back and admire your work.

  10. Time to Clean Up!

    Collect all the sticky newspapers, and garbage to take out to the dumpster. Caution, last weekend I found a rattlesnake sunning itself by the dumpster at the Hunting & Fishing Club, so watch your feet, 'cuz they can crawl under those dumpsters!

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This page last modified 6 September 2007.