Home > Knowledge Base > Material Information > Mandrel Dip Molding of Latex Tubing

_What is latex anyway?_

To put it simply, latex is the sap of the rubber tree. Most of the worlds rubber trees are grown in the equatorial region of southeast asia. The latex is harvested in much the same way as maple syrup. The bark is stripped from a small section of the tree trunk in a spiraling pattern. The tree will secrete latex from the bared trunk which runs down and along the spiral cut bark until it reaches the collection vessel.

_How does liquid latex become a speargun band?_

There are a number of manufacturing processes used to make products from natural rubber. The process that best preserves the elastic and tensile properties is called dipping manufacturing or dip molding. It is the process by which rubber gloves, condoms, balloons and latex tubing are produced. Dip molding is superior to extrusion for speargun rubber because of the way it aligns the bond structure at the molecular level. In the case of latex tubing a long mandrel is used as the mold. It is dipped in liquid latex which forms a thin uniform layer on its surface upon removal. The layer is allowed to cure and the process is repeated until the desired diameter is attained. The process is very similar to candle making. Precision is limited and thus the tolerances that rubber manufacturers specify for their tubing. The two U.S. companies that manufacture latex tubing specify a tolerance of +/- 0.02in for medium sized speargun tubing. We list tolerances for every diameter of tubing we sell on the manufacturer's specifications page in this same section of the Knowledge Base.

_Why can't I buy I buy a big continuous roll of speargun tubing?_

One question we hear often is, "Can I buy a continuous spool of tubing?". Most people assume that speargun tubing, like virtually every other kind of tubing, is extruded out of a machine in unlimited lengths. That would be nice and it would save us a ton of work but a draw back of mandrel dipped tubing is that the product length is limited by the length of the mandrel. Furthermore, defects such as bubbles and lumps are common. These defects must be cut out of the finished product. As a consequence, latex tubing is sold by manufacturers in random lengths. Tubing segments rarely exceed 60 feet and average between 20 and 30 feet.

_The Spearit advantage_

Most retailers of speargun tubing will fill an order of 50 feet, with as many as 3 segments totaling 50 feet. At Spearit, we sell a lot of tubing. In a normal year we will take 4 - 6 deliveries, each totaling in the thousands or tens of thousands of feet.

There are several advantages to this high volume for our customers:

  • Fast turnover insures fresh tubing.
  • Large incoming orders allow us to sort and trim the tubing into the rare, long, continuous segments that we offer.
  • Finally there are the savings of quantity purchasing. Savings that we pass on to our customers with our everyday low prices.