Soft Plastic Plastisol Mix Calculator

The science of pouring soft plastics. Pouring soft plastic lures feels like magic, but it is actualy just applied chemistry and geometry. There’s only geometry and chemistry.

You begin with a clear liquid plastisol, sprinkle in some salt to control sink rate, then add color to make ’em visible. Ideal result will sink instead of float and won’t tear where it touches the hook. The calculator (above) figures all that stuff out for you. This means you don’t have to estimate what percentage of your base resin has been absorbed by additives and wasted during sprue.

How to Pour Soft Plastic Lures

Additives such as fine salt makes the plastisol denser by increasing mass and thereby displacing some of the polymer resin. This is important since the less resin there is, the less flexible finished bait will be. While you may achieve a faster sinking stick bait, they can get brittle in cold water if you don’t take the compromise into consideration. As you can see from table on page, each grade has its own response to modifiers.

There are other variables that cause problems, such as hardness. For instance, maybe you like how a certain medium plastisol feel in the cup so you choose that grade. Then you adds a certain amount of softener to get a particular texture. The addition of that softener drop the durometer substantially and reduces strength of the lure’s nose. A compromised-nose bait won’t last through multiple hook set.

With your inputs for both hardener and softener, the calculator will adjust the expected hardness index to give you look at what the physical feel will be prior to heating the mix.

Most people mess up their pours when it comes to calculating volume. When they measure one cavity with water, they don’t factor in splatter during pouring, injector nose, or the runners. Typically, you can lose as much as 10-15% of the batch to trim and sprue in most molds. If you’re only calculating how much volume finished baits have, you’ll find yourself running out of mix half way through your final pour. By adding an overage buffer, you’re sure all cavities gets filled to capacity without short shots ruining your whole production run.

There is a fine line with regrinds. Using scrap baits and leftover sprues is good for not wasting plastic and money. But it adds inconsistency to your batch. Regrind has shorter polymer chains then brand new material which will change some things like stretch and clarity. If you have lots of regrind, those paddle tails may gets cloudy or be so brittle that they snap instead of bend. Keep the percentage of regrind reasonable to see the cost savings. This way, you won’t compromise structure of new lures.

While they may appear insignificant; like a drop of scent and a couple drops of color (it all add up). Colorants (if used heavily) will change viscosity a bit as well as increase volume. Scent or slickness oils will not cure with the plastisol, and they can be affected by time (leaching out) or how the bait feel as it moves through water. You must account for these small details on the tool, so every drop counts when you need precision.

This shift in understanding how things work change your workbench experience. From there on out you are engineering rather than guessing. What was a chance event turns into a predictable result with each pour. You know how much softener you need to lower hardness and how much salt is needed to raise the density; it’s all under your control when making finished product.

It is that control that makes the difference between those who just dabble and those who make quality lure every time. You’re not building a bait that merely resembles a fish. You are designing one that holds up to rigging, acts right in the water and does what it’s supposed to do when pressured. That requires careful balance with all those factors where every drop counts.

The baits holds up from cast to cast. They sink the way they were intended and hook the way they’re meant to be.