2-piece pouring problems

[HJS]

Finally, after 4 failures, I was able to make a pretty decent 2-piece mold using PoP and 4" paddletail Bass Assassins as masters. No bubbles and surfaces were smooth. I tried my first pouring using remelted old soft plastics. I also preheat my mold in the oven set at 170F.

2 PROBLEMS:

1 - My pour hole seemed to clog a little too easily regardless how slow I poured. I heated the plastic about as hot as I dared using a microwave. My mold does have a tiny vent holes at the bottom that seemed to worked as planned. My pour hole was made using a 13/64th" drill bit. The pour hole is about as short as it can be, maybe 1/8" long. I used a large counter-sink drill to flair the pour end to facilitate pouring. Should the hole be bigger in diameter? What size pour holes do you all use?

2 - I did get a few successful lures... very nice if I must say so. But when I removed them from the mold and cut the excess off at the pour-end, I saw that shrinkage had caused a small hollow that extended about 3/8" into the lure. How can I avoid shrinkage from wrecking my pours???

Thanks

[nova]

# 1 you have to pour right into the hole without touching the sides.

# 2 try to pour the plastic as cool as you can and use spring clamps to hold the mold tightly together. Finally don't be in a rush to open the mold.

www.novalures.com

[Willy]

#1 My pour holes on my 2 part molds are about as thick as a pencil. I have to cut off the pour hole piece anyway, so I figure, who cares how fat it is?

Nova (as usual) is right, it is imparative to aim your pours exactly down the middle, if you don't do that, you may as well start again. The plastic that hits the edge of the hole will cool, no matter how warm the mold is, and you're in trouble from there. All I can say, is it takes practice. Lots. If it helps, find somthing tall and stable to rest your pouring arm on when you pour to stabilize your pouring hand so as to 'hit the mark.'

#2 Shrinkage happens. Nova is right, if the mold moves or spreads, it will cause a little vacuum and cause the tip to suck-in, and make the hollow tip you were lamenting. Clamp it, or use a really strong grip.

To fill the tip, what I do is keep the plastic hot and keep topping off the hole. You will need to develop your timing to let the first pour to cool and shrink, then top off the hole with a little more hot plastic, let it sink down in there, and top off again. A hint; I keep a little harder plastic hot in a seperate cup, and top off with that, it makes the tip of my lure harder than the rest to avoid hook damage in the tip, especially important on worms and flukes. But figure out your timing, and top off the hole, that'll help you out.

#3 listen to Nova, when I was beginning, he was willing to give me tips that helped me learn what I was doing, and I think of his advice every time I pour. Read thru the forums and check his posts. It's worth the time of any and all pourers.

Willy

Edited June 16, 2008 by Willy

[Vodkaman]

Nova and Willie have comprehensively covered your question. I would add, that seeing you are making the molds yourself, why not introduce a larger pouring cone or funnel. This will allow you to pour extra plastic, which will get drawn down as the plastic cools. This will simplify the pour and eliminate any possibility of cooling cracks.

From reading your post, I assume that you are drilling your pour hole after making the mold. There is nothing wrong with this, I suspect most construct molds this way. I mold my pour holes and vents with rolled plasticine, before pouring the PoP. I find it simpler and less nerve wracking than drilling.

[HJS]

Thanks guys, I knew you'd come thru.

nova - I use a strong rubber band to hold the halves tightly together. And you're right, the few plastics that came out OK were poured without the plastic touching the sides of the pour hole.

Willy - And yep... now I know I need a bigger pour hole. My pour holes are definitely smaller than a pencil... like I'm trying to pee in a coke bottle at 6 feet. Should be easy to bore out a bigger hole. I was thinking that I should keep topping off as the plastic cools to minimize shrinkage. But thats difficult when I can't see whats going on inside the mold and don't know how close I am to the top. A bigger hole, topping off and lots of practice should solve most of my problems.

Vodkaman - Yes, I drilled my vent/pour holes after the plaster had hardened. I held the 2 halves together tightly as I drilled the holes. Worked out well, but does take a delicate touch.