The entomological collections community should be aware that there has
been a significant change in the production of polyethylene Ethafoam
made by Dow Chemical Co. This is the foam that many/most entomological
collections use in unit trays for pinned collections. The story is a bit
complicated; however, due to the flammability of a chemical releasing
agent (isobutane/pentane) used in the production of Ethafoam, Dow
patented a new Rapid Release Process technology to allow for off-gasing
of this flammable chemical and so that it could be safely shipped.
Unfortunately, for entomologists, this new process means that small
holes (size of the diameter of a #5 pin) are laser drilled into the foam
in rows spaced about 3/8 inch apart in both directions. This means that
most pins, if they are pinned into one of these holes will swivel and/or
fall out (if tilted). Random pinning will probably only hit a hole
exactly once every 25-30 times; however, this is still potentially
problematic. For most uses of Ethafoam (i.e. cushioning objects) these
holes are not problematic, but for insect collections they are.This new
process and production of "holy" Ethafoam only began in about
January/February of this year.

Apparently there are polyethlene foam manufacturers out there who do not
yet drill holes in the foam (BioQuip has apparently found one). However,
be warned that many of the polyethylene distributors are selling "holy"
foam in sheets or pre-cut. If the other foam manufacturers begin to
produce "holy" foam due to its flammability, entomological collections
may be in trouble.