Air trapped..

[Jared]

I am getting air trapped in my bait when i pour them. I am pouring large soft baits. I think my material is to hot when i pour it. What is the best method to pour them solid.

[GMan]

You may need vent holes where the air bubbles trap. See some of the how to videos. Also be sure to pour slowly. There are more experienced guys than me on this board who may be able to offer better advice. Good luck.

[aka anglinarcher]

If the plastic is not scorching it is not TOO hot. GMan is dead on about the vent holes, pour rate, and the how-to videos.

It also may be possible that you are not leaving a big enough reservoir of material at the pour hole to allow for shrinkage. This will leave what looks like air bubbles near the pour hole, often inside the bait, near the pour hole.

Where are the air bubbles forming at? Can you perhaps give us more detail?

I'll bet others can offer suggestions as well.

[Jared]

The air is usually in my bait center. typically just below the pour hole. I have 3 hole drilled in the top of my mold to pour and allow air to escape.

[aka anglinarcher]

This does sound to me like you are shrinking as it cools but there is not enough hot material to pull down and fill the void. The edges cool and hold shape, leaving an air bubble in the middle, just under the pour hole.

I suggest increasing the size of the reserve around the pour hole so that the plastic can shrink and pull more hot material down into the hole.

I also suggest calling Mike at Alumilite and asking him directly if this does not fix your problem.

[Jared]

Ok thanks. I will give it a try.

[Mike - Alumilite]

Often if the pour hole and vent holes are too small in a large bait the material in those vents cools and hardens before the bigger mass inside cools and shrinks which caps it or seals it off. If this happens the material can not "pull" or shrink out of the vents because they have already cooled/hardened. How to confirm if this is what in fact is happening ... IF the material has the detail from the mold surface but looks like it sucked into itself ... this means it was full but then shrank when it cooled. If you have an air pocket and there is no surface detail it would probably be glossy, this means it was a true air pocket and the air was trapped and could not escape when pouring. If you are using Alumidust and the air pocket has no color on it and there is still Alumidust on mold, it was a true air pocket. If the Alumidust is all cleaned off the mold and it sucked in on itself, it shrank meaning your vents and pour holes cooled and sealed the material inside and forced it to shrink in on itself.

So what do you do? Two things ... first pour it in layers allowing it to shrink and then pour more and continue this process until the entire mold is full. You don't have to wait until it has completely cooled and hardened but rather layer it every few minutes. This can usually be done in 2 or 3 pours max and it will fill perfectly because it minimizes the shrink of each layer due to less volume of each layer. The other thing is to pour it only to the bottom of the pour hole and clean the cooled reminents out of the pour hole while the material in the mold is still curing so it is not capped off or sealed but actually open to shrink from the pour hole area. Then simply top it off after the material in the mold shrinks away from the pour hole. Basically you are trying to prevent the pour hole from sealing and closing the cast in which allows it to shrink from that area. As long as you can keep the pour hole open or molten, it will shrink from that area and not from inside the mold creating a divet in your lure.

Hope that makes sense. Good luck and let us know how it goes.
Mike

[dahlberg]

Sorry I'm late in replying, but I've been away for a couple of weeks.
I think you've got it solved with the shrinkage thing.
You can get tiny air bubbles if the Alumisol is a little too hot or the mold has moisture in it, but the void you are describing sounds more like shrinkage to me.
I would suggest keeping an eye on the material in the first several minutes after pouring and adding molten alumisol as you see shrinkage occurring. It's what I do because it happens on every large soft plastic mold I have!
best
L