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How to make Vertical pour full round silicone molds

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This works great with "no longer available" or hard to find soft plastics like the 4" spade tailed grub below

using a mold box (I made mine out of LEGO's sealed on the inside with clear packaging tape) and Platinum cure silicone since the viscosity is very thin and picks up detail without bubbles but is so thin it will leak out of a poorly sealed mold box .


Picture below shows a cutaway of vertical mold box with bait hanging from plastic cone glued to this strip of wood serving as sprue to pour plastic .

A piece of spinnerbait arm wire is imbedded in cone then pushed into grub body to hold in place . A small tungsten worm weight can be hung on a sewing pin and inserted in tip of tail to insure bait hangs straight (if needed) but this also makes a great vent hole 



Following manufacturers directions mix and then slowly pour silicone into mold box until desired height is reached 

If desired you can slowly raise and lower bait in and out of silicone a few times to make sure there are no bubbles sticking on bait 

Demold from box when silicone is fully cured and gently pull master from mold 

Pam spray can be worked around sprue hole and top of bait to make removing bait easier 


demolded mold is pictured below (note how mold box LEGO brick shapes were picked up thru sealing take by silicone )




In picture below is a hard master made from 2 part polyurethane casting resin poured into new mold 

Polyurethane casting resin can then be sanded or built up /shaped with epoxy to alter original factory bait to make a new design of your own .

Make sure to fish with and are happy with your new design before wasting any expensive mold material ! (been there done that)

If you ready to start making multi-cavity molds of your new design you can make a new 1 cavity mold with your hard master and pour multiple polyurethane hard copies oriented sprue side down in the sprue box for a multi-cavity mold of your new creation for production without the expense or delay of having an aluminum mold custom made .





Pictured above is the original Methiolate grub , Hard master with sprue made in new mold , and new green pumpkin grub poured in new mold shown in back ground .   With mold positioned with sprue hole up  you can pour plastic into mold with pouring cup . If you end up with a void in cavity or suspect you might you can gently squeeze mold towards the bottom forcing air bubble out then pour more hot plastic into the mold .

In conclusion the pro's are this method allows one the ability to rapidly produce and modify prototype soft plastic baits with minimal features with hand pouring in a semi clear mold you create  . The cons are the cost of the Platinum cure silicone and the limitation of shapes you can pour and still get finished baits out of the mold 



Edited by jigmeister
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