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Concrete Mold Making | Page 3

concrete mold making 15

Figure 13


My plan worked - with the help of a fan blowing across the wet latex I was able to shorten the drying time to about an hour and a half per coat. At this stage there are ten coats applied on the way to fourteen. But now I must add reinforcement to make the latex rip resistance and to triple its life. So now is the time to embed cheese cloth strips. The eleventh layer of Kreemtex latex is brushed on and the cheese cloth strips are cut and laid down on the surface.

concrete mold making 16

Figure 14

  A coat of Kreemtex latex is added on top of the cheesecloth and the next strip of cheese cloth goes down. I must be careful not to leave any air bubbles or separation between the latex surface and the cheese cloth or it will be a weak spot in the final mold. I carefully take my brush to the corners and edges and press out all the air repeating this three or four times. Once the cheese cloth is down and coated with Kreemtex there will be three more layers of latex applied to finish the latex portion of the mold. To be Continued . . .
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Figure 15


Finally finished the latex mold. There are now 15 coats of Kreemtex applied. The latex is about 1/4-inch thick (see inset). I will begin the next phase tomorrow by adding a rigid support shell mold made of fiberglass. The support shell could be made with CastRite plaster, but it would need to be 3-inches thick. That means it would be very heavy. Since I have to make 52 castings in concrete when the mold is finished, having a lightweight shell mold will make molding easier to handle.

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Figure 16


Figure 16. is a close up showing the thickness of the finished latex mold. It now waits for the application of a ridgid shell mold to support the weight of the concrete during the casting phase.

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Figure 17


Building the rigid fiberglass support shell begins by assembling all the material. This includes: 1) polyester resin and its hardener; 2) wax and PVA mold release; 3) A bubble roller and a squeegee; 4) Rubber gloves; 5) mixing buckets; 6) mixing sticks; 7) a measuring cup; 8) Aacetone to soak the squeegee and roller in to keep the clean and resin free; 9) scissors; 10) box cutters; and 11) some rags. I'm also outdoors because the polyester resin odor is too strong to use inside.

concrete mold making 19a

Figure 18


I begin by covering the latex mold thoroughly with a mold release wax.

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Figure 19


When the wax is dry I add a second type of mold release which is a liquid. I paint on a coat of PVA release. This needs time to dry.


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