Using the correct alloy makes a difference
There are two general types of lead alloy, “soft lead” (mostly pure lead) and “hard lead” (an alloy of lead and a harder metal.) Pure lead melts at 621 degrees F. and has excellent pouring characteristics at 700-800 degrees. A hard lead alloy may solidify too quickly and require more effort to mold good parts.
Soft lead can usually be identified by pressing or scratching your thumb nail into it. If it scratches easily, it is probably soft lead. If you can’t scratch it at all or only with pressure, it is not soft lead. Since soft lead has a relatively low working temperature (700-800 degrees for most applications), it is easy to use. Small jigs and sinkers, as well as spinner jig lures, are much easier to cast when using soft lead. Soft lead is a necessity for use with bendable type sinkers such as split shot or pinch-on sinkers.
HARD LEAD (Tire Weights, etc.)
Because of its molding difficulties, the use of hard lead is not recommended in Do-it molds. Hard lead refers to a lead alloy that has one or more other metals added to make a metal that is harder than pure lead. The other metals can cause the alloy, when poured into a mold, to solidify or “freeze” at temperatures where pure or soft lead is still fluid. Consequently, more heat or a faster rate of pour may be necessary to get complete castings with hard lead. The chief appeal of a hard lead alloy for sinker and lure making is that it can often be purchased at less cost than soft lead. This advantage can be offset by difficulty in molding the metal. The most common source of hard lead is used wheel or tire weights. Since the main function of wheel weights is weight, they often contain a lot of tramp elements. Wheel weight compositions vary widely. If you acquire hard lead, remember that it will likely require more experimentation and effort than soft lead to pour complete castings. It may work well for some medium and large sinkers and lures, but avoid its use in the more difficult to mold small jigs and spinner baits. Do not use hard lead to make sinkers like split shot or pinch-on types. These sinkers must be easily bendable to work correctly. A hard lead alloy will make these sinkers too stiff to bend.
Best molding results will be obtained using soft lead or a lead alloy that is at least 98% lead. Following is a listing of various types of lead and their approximate percentages of tin or antimony.
Commercial Pig Lead - 99.6% lead; Cable Sheathing - 98.5% lead; Battery Lead - 90% lead and 10% antimony; Plumbers Solder - 67% lead and 33% tin; Wheel Weights - (varies) may contain anything from aluminum to zinc, in addition to antimony and lead; Type Metal - 82% lead, 15% antimony and 3% tin.
Effects of other elements to a lead alloy:
Antimony: Adds strength and hardness. May cause premature solidification, wrinkles or other molding flaws. Avoid metals containing antimony.
Zinc: Makes a lead alloy sluggish, limits its ability to flow and requires a higher casting temperature. It can cause roughness, porosity, voids and a grainy or frosted appearance on castings. Avoid metals containing zinc
Aluminum and Iron: Effects castings the way zinc does. Avoid!
Tin: Adds ductility and strengthens lead. Tin melts at a low temperature, 449 degrees F., and generally improves a lead alloy. With some experimentation, pure tin can be used to make lures and sinkers. Tin is an expensive metal, but has no known environmental or health risks. A tin object will weigh only 2/3 that of the same object made of lead. Example: a 3/8 oz. lead jig will only weigh 1/4 oz. if made from pure tin. Tin could be an attractive lead substitute if it was not so expensive and difficult to obtain.