DIY - The Finished Product
Now that you have mastered the flat one piece mold, it’s time to advance to a two-piece mold.
Two-piece molds are used to create full-round bait with no flat sides. There are pros and cons to a two-part mold. The pro is that in some cases you get a more realistic lure that is shaped on all sides. One of the cons is that you have to pour in one end of the mold and you are at the mercy of gravity to fill the cavity. For instance, a bait with a curly tail like a large twister tail. The tail becomes a large curly “J” shape and as you can envision, the plastic will only fill the bottom of the “J". Unless you have some means of injecting the plastic under pressure you will get short-filled tails. I have tried putting the fill spill on the bottom of the “J” and pouring upside down with little success.
But for straight tailed baits and things like swim baits it works great.
So for our example, let’s start with a pike sized swim bait.
As in a one-part mold, find a suitable sized container and mix up enough plaster to fill about half the mold. Pour the plaster in the container on a level surface.
Now, here is the trick!
|Making a the mold|
You have to carefully place your master exactly halfway into the wet plaster. I say that this is the tricky part because if you put the master in too soon, it will sink into the plaster. If you wait too long you won’t be able to get it into the plaster without making the plaster bulge around the edges.
|Original half way in.|
I can’t give you a magical time to wait. Every batch of plaster is different and it’s an acquired “feel” for the material. Don’t be disappointed if you mess up a batch. Plaster is cheap!
Let that half of the mold cure overnight.
The next day you will be able to pour the second half of the mold. So that the two halves line-up correctly, you will need pins or deformations in the first half. My favorite method is to make cone shaped divots using a counter-sink bit. Drill them in the unused portions of the mold. Two or three spots are enough.
|Aligning the mold|
Now you are ready to apply a release agent to the face of the mold so that the two sections will separate. Simple petroleum jelly is all you need. Rub a thin coat over the entire face of the plaster and the master. Make sure everything is covered thoroughly.
|Apply Releasing Agent|
Now mix up enough plaster to fill the remainder of the mold. Mix this batch up a little more watery than normal. This allows any air bubbles that may be in the mold surface or around the master to release and float to the surface. It also insures that plaster gets into every nook and cranny. You may even need to tap the sides a little to help the bubbles pop free.
|Smoothing the mold|
Let that cure overnight.
The next day you can unmold the mass from the container. Gently separate the two halves. If you have the petroleum jelly on correctly, you should be able to get a good grip on each half and pull them apart. If you have trouble, you may need to slide a thin putty knife in the edge and gently pry them apart.
Remove the master and let both halves cure for several days before you start applying the epoxy sealer to the lure cavities. The procedure is the same as the one-piece mold except do not get the epoxy on the faces of the mold. This could cause the two halves to fit together improperly. Apply it to the lure cavity only.
|Sealing the mold|
Before you start epoxying you will need to add a pour spout to the mold. I use a round or half round file till you make a hole large enough to pour into. This pour spout or sprue will also need the epoxy coating.
Once you have three coats of epoxy (thinned with acetone) on the mold, you are ready to pour some full round baits.
|The mold coated and ready to go.|
Mix and heat up the plastic as previously described. Hold the two halves together with a rubber band. Pour the plastic slowly until the mold overfills slightly. Wait 10 or 15 seconds and top off if needed.
Have a place where the mold can stand upright till it cools. When it cools, (2-5 minutes depending on the size and volume of the bait), remove the rubberbands and remove the bait.
|The Finished Product|
Each two-part mold will have a personality of its own. Some baits pour best holding the mold straight up and some on a slight angle. Some need a small relief air path cut in and many don’t. This can be done on one half of the mold with a hacksaw blade.
All in all making a two-part mold may be a little more complicated, but pouring them is very easy.
Good luck and enjoy making soft-plastic baits.
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Last updated on ...July 13, 2008