characteristics of nut
shells and fruit pits all shell products do not necessarily meet the
same specifications, nor have the same uses.

Industrial Cleaning and Finishing

Oil, dirt, corrosion products, stain, paint, grease and the like can be
removed from metal surfaces by air-blasting with soft grits prepared
from shells of walnuts, pecans, peach pits, and similar residues. This
method was developed originally for the Navy to use grits from
corn-cobs for cleaning aircraft engines and parts. The method is
inexpensive and foolproof because surfaces are cleaned without change of
dimensions. No pitting or abrasion, such as produced by sand blasting,
occurs. The method is particularly useful with mild steel, nonferrous
metals, alloys, and parts that must be maintained at close tolerances.
Modifications of the blast method are used in finishing molded plastics,
metal die-castings, and machined parts. One manufacturer of precision
instruments states that his company saves $100,000 a year in finishing
parts with shell grits.

Many stamped metal articles and molded plastics are deburred, cleaned,
burnished, and polished by tumbling in drums containing shell grits.
Various grades of grits are required depending upon the nature of the
pieces being finished.

Fillers for Plastics and Plywood Glues

The Laboratory has studied the use of shell flours for use in plastics
and plywood glues. Many of these flours are now in regular commercial
use. Flours for these applications are prepared in various grades, all
finer than 100-mesh. Use of these flours not only improves the
properties of the final products but also reduces the cost of the
products. Molded plastics prepared with fine flour from English walnut
shells have exceptionally fine surface finish.

Insecticide Carriers

The insecticide field provides a good outlet for shell flours. Flour
from walnut shells was the first of this type of material to be used for
this purpose. Often the active ingredient in a finished insecticide is
present in quantities of less than 1 percent. Custom grinders should
plan to recover the flour as a co-product of their operations rather
than attempting to grind to flour alone.

Explosives

Large amounts of shell grits and meal are used as diluents in the
manufacture of dynamite. Material for this use ranges in size from No.
10 to No. 100, the requirements of the individual manufacturers falling
within much narrower limits as to si