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We must give American ingenuity credit. Those once vast piles of discarded and worthless tires have been given new life. Shredded they are now sold as playground mulch, an added ingredient for road surfacing for smoother driving, septic system drain fields, and even gravel replacement among other uses. But the real purpose of this article is not about old tires. It is to describe how another commodity that was simply tossed into landfills has been developed by creative entrepreneurs into an extraordinarily useful product, particularly for use in our industry.
Think of pecan pie and your mouth waters for that popular cloying sweet southern style pastry. But think about the pecan shells for a moment that nestled and protected the pecans. They too were once treated like old tires, simply hauled out and dumped wherever they could find space. Not so anymore pecan shells are a hot commodity. They actually now have value after they are separated from the pecan.
The shells are ground into many products ranging from a coarse grind to a very fine particulate made up of individual cells. It is the uniqueness in the basic cell design that makes the product beneficial. Most fibers are long and thin; however, the pecan shell is made up of rounded oval shaped cells called sclereids. This type of particle shape is very free flowing and allows ease of dispersion when mixed with other ingredients. Another key property is the low ash content which results in a non-abrasive fiber.
Coarsely ground pecan shells are used as mulch, in the grill to add smoked pecan flavor and even as an earth-friendly biofuel for the wood stove. Ground into a pecan shell flour they are used in fracking, and as beauty product additive as examples. In the molding and cast industry ground pecan shell flour (ground to 325 mesh screen fineness) is used to created simulated wood when combined with a bonding element such as polyester or polyurethane resin. A ratio of one third pecan shell flour by weight to two-thirds resin is a typical formula for bonded wood.
It is also used as a filler or extender with casting resins. As adding the much less expensive flour helps extend the casting budget while using less of the more expensive resins. It can be also be used as a thickener in liquid latex so that latex can be applied to vertical surfaces without running.
But one downside of pecan shell powder is that it is hydroscopic. That is it retains moisture. So to use it with resin it must be thoroughly dried to prevent the resin from foaming (resins don’t like moisture), This can be accomplish by laying out the pecan shell flour on a cookie sheet and placing it a low temperature oven (150 F) for about one half hour. If you use pecan shell flour as a latex thickener though this isn't necessary as liquid latex is also water based.
What was once tossed aside is now very useful in the studio thanks to an entrepreneur’s bright idea to reclaim a waste product. It is no longer free as there is labor and overhead involved in grinding the shells into flour. But it is still a very economical additive to consider.