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Preparing the Mold Block for
Glass Facing the Mold Cavity Side
By the end of this chapter; you will have made a Master Plug Shape Capture Mold that looks like EXAMPLE #1. This basic mold can be further developed into a limited prototype production mold for making test and developemnt copies of your lure design.
The real nifty thing about using a polyester resin base Mold & Casting Compound to make basic mold blocks is that it is extreamly forgiving. If a mistake is made in cutting and pressing the lure body cavity; the mold block can be re-filled with M&CC, re-cut, and re-pressed a limitless number of times.
I have used obsolete lure design mold block sets to begin developing an entirely different lure design. Try that with aluminum, steel or silicon molds.....?
18. Your Mold Block should now look like this: Fig. 11. The mold block and master plug should appear to have similar proportions.
Perhaps you are wondering why I didn’t instruct you to cast the sculpting block larger so it may be cut and divided into two or more sculpting blocks. It is the nature of Mold & Casting Compound to shrink slightly during the curing process (up to 3% depending on the amount of catalyst added). Shrinking may cause the material to warp or bend adding more time and labor to the next step: “Glass Facing”. “Glass Facing” is the term we use to describe what will be truing (making perfectly flat) and polishing the cavity side of the mold block. In BOOK Two, Advanced Mold Making, we will discuss different ways to glass face much larger blocks of Mold & Casting Compound.
19. With #120 wet sand paper; wet the sand paper on both sided. Place the sand paper on the glass work surface. Place the mold block on the sand paper with firm and even downward pressure, rub (sand) the mold block cavity side until it has a uniform and flat surface. Do this to all six sides. It is OK to round-off outside edges slightly. Add more water to the sand paper as needed. Fig. 12.
Repeat this mold block making proscess to cread two mold halves. The two mold block halves should be as near the same size as possible. Any slight difference in size can be adjusted after partial assembly.
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